Wind/Solar Electrics ??? [Archive]

RST Engineering

December 14th 05, 11:02 PM

After much thought and ponderance, I've come to the conclusion that to
electrify the hangar using Pacific Gas & Electricity (PG&E -- Pigs, Goats,
and Elephants) isn't clever. By the time you get them to hang a meter
($5k), trench from the power pole to the end of the row of hangars, conduit
romex to 35 hangars at a cost somewhere around $50k ($1500 per hangar), and
then pay the monthly electric bill, you could buy a hell of a wind/solar
system and perch it on the (flat) hangar roof.

Before I flail about gathering data, has anybody on these ngs actually
installed a design whereby a hefty solar panel charges a hefty battery to
run a hefty inverter? It doesn't have to be absolutely "clean" sinewave
power as all we are running are fluorescent shop lights (about 400 watts
worth), every now and again a small compressor, a small drill press, a small
grinder, but none of these last few at the same time.

My hit on it is that a 2 kW inverter would be more than enough to handle the
AC side of it, and a bank of 12 volt truck batteries would work for the DC
side of it, but there are the problems of parallelling large batteries, how
to combine the outputs of solar cells and wind generators, and a reasonable
source for all this stuff.

There are issues around protecting the solar cells from hail, which we do
get from time to time, battery acidic gases inside a hangar where a very
expensive lump of aluminum is sitting for months on end, sizing the solar
cell and wind generators, and other considerations along these lines.

Comments appreciated.

Jim

Jim Thompson

December 14th 05, 11:09 PM

"Hefty" solar panels don't come for cheap.

Do you have regular enough winds to use for battery recharging?

On Wed, 14 Dec 2005 15:02:56 -0800, "RST Engineering"
> wrote:

>After much thought and ponderance, I've come to the conclusion that to
>electrify the hangar using Pacific Gas & Electricity (PG&E -- Pigs, Goats,
>and Elephants) isn't clever. By the time you get them to hang a meter
>($5k), trench from the power pole to the end of the row of hangars, conduit
>romex to 35 hangars at a cost somewhere around $50k ($1500 per hangar), and
>then pay the monthly electric bill, you could buy a hell of a wind/solar
>system and perch it on the (flat) hangar roof.
>
>Before I flail about gathering data, has anybody on these ngs actually
>installed a design whereby a hefty solar panel charges a hefty battery to
>run a hefty inverter? It doesn't have to be absolutely "clean" sinewave
>power as all we are running are fluorescent shop lights (about 400 watts
>worth), every now and again a small compressor, a small drill press, a small
>grinder, but none of these last few at the same time.
>
>My hit on it is that a 2 kW inverter would be more than enough to handle the
>AC side of it, and a bank of 12 volt truck batteries would work for the DC
>side of it, but there are the problems of parallelling large batteries, how
>to combine the outputs of solar cells and wind generators, and a reasonable
>source for all this stuff.
>
>There are issues around protecting the solar cells from hail, which we do
>get from time to time, battery acidic gases inside a hangar where a very
>expensive lump of aluminum is sitting for months on end, sizing the solar
>cell and wind generators, and other considerations along these lines.
>
>Comments appreciated.
>
>
>Jim
>

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Dave Stadt

December 14th 05, 11:10 PM

"RST Engineering" > wrote in message
.. .
> After much thought and ponderance, I've come to the conclusion that to
> electrify the hangar using Pacific Gas & Electricity (PG&E -- Pigs, Goats,
> and Elephants) isn't clever. By the time you get them to hang a meter
> ($5k), trench from the power pole to the end of the row of hangars,
conduit
> romex to 35 hangars at a cost somewhere around $50k ($1500 per hangar),
and
> then pay the monthly electric bill, you could buy a hell of a wind/solar
> system and perch it on the (flat) hangar roof.
>
> Before I flail about gathering data, has anybody on these ngs actually
> installed a design whereby a hefty solar panel charges a hefty battery to
> run a hefty inverter? It doesn't have to be absolutely "clean" sinewave
> power as all we are running are fluorescent shop lights (about 400 watts
> worth), every now and again a small compressor, a small drill press, a
small
> grinder, but none of these last few at the same time.
>
> My hit on it is that a 2 kW inverter would be more than enough to handle
the
> AC side of it, and a bank of 12 volt truck batteries would work for the DC
> side of it, but there are the problems of parallelling large batteries,
how
> to combine the outputs of solar cells and wind generators, and a
reasonable
> source for all this stuff.
>
> There are issues around protecting the solar cells from hail, which we do
> get from time to time, battery acidic gases inside a hangar where a very
> expensive lump of aluminum is sitting for months on end, sizing the solar
> cell and wind generators, and other considerations along these lines.
>
> Comments appreciated.
>
>
> Jim

Seems running a generator would be simpler and cheaper.

RST Engineering

December 14th 05, 11:32 PM

"Jim Thompson" > wrote in
message ...

> "Hefty" solar panels don't come for cheap.

That's true, but they are about half the price that they were about ten
years ago. That said, a small Honda generator when you really need a couple
of kW and a few watts of solar panel to keep the aircraft battery batting
and the keepalives on the radios keeping may be the hybrid way to go.

> Do you have regular enough winds to use for battery recharging?

Well, we are at 3000' on the west slope of the Sierra on the top of a small
hill with nothing (literally) between us and Japan except for a wire fence,
and it's down {;-) We get some decent winds, but nothing you can count on.
Today, for example, the peak wind was somewhere around 7 knots and the
average somewhere around 3 or 4 knots. Then again, last week we had a
howler come through here at 40 knots and last for a day. Nothing
dependable.

Jim

RST Engineering

December 14th 05, 11:33 PM

With a small solar panel to keep the continuous load going, not a bad way to
go.

Jim

> Seems running a generator would be simpler and cheaper.
>
>

Matt Whiting

December 14th 05, 11:46 PM

Newps

December 14th 05, 11:54 PM

I use Trojan T-105 6 volt batteries in my 5th wheel. They are far and
away better than any automotive or deep cycle 12 volt battery for even
several times the price. A friend not far from here has a solar setup
like you are contemplating at his hangar. I also have a solar panel on
my camper. Here's a couple of links to get you started. You don't have
to worry about hail, until it comes down the size of softballs they are
impervious to it. I don't know what problems you mean with paralleling
batteries but as long as all the batteries are the same they charge just
fine. Just make sure you have a charge controller. Mine is a 7 amp
because I only have a 75 watt panel. A few hundred watts and about six
6 volt batteries would take care of you.

http://www.trojan-battery.com/

http://www.solar-electric.com/

RST Engineering wrote:

> After much thought and ponderance, I've come to the conclusion that to
> electrify the hangar using Pacific Gas & Electricity (PG&E -- Pigs, Goats,
> and Elephants) isn't clever. By the time you get them to hang a meter
> ($5k), trench from the power pole to the end of the row of hangars, conduit
> romex to 35 hangars at a cost somewhere around $50k ($1500 per hangar), and
> then pay the monthly electric bill, you could buy a hell of a wind/solar
> system and perch it on the (flat) hangar roof.
>
> Before I flail about gathering data, has anybody on these ngs actually
> installed a design whereby a hefty solar panel charges a hefty battery to
> run a hefty inverter? It doesn't have to be absolutely "clean" sinewave
> power as all we are running are fluorescent shop lights (about 400 watts
> worth), every now and again a small compressor, a small drill press, a small
> grinder, but none of these last few at the same time.
>
> My hit on it is that a 2 kW inverter would be more than enough to handle the
> AC side of it, and a bank of 12 volt truck batteries would work for the DC
> side of it, but there are the problems of parallelling large batteries, how
> to combine the outputs of solar cells and wind generators, and a reasonable
> source for all this stuff.
>
> There are issues around protecting the solar cells from hail, which we do
> get from time to time, battery acidic gases inside a hangar where a very
> expensive lump of aluminum is sitting for months on end, sizing the solar
> cell and wind generators, and other considerations along these lines.
>
> Comments appreciated.
>
>
> Jim
>
>

Dave Stadt

December 14th 05, 11:54 PM

The generator can provide battery charging capability should the sun or wind
let you down.

"RST Engineering" > wrote in message
...
> With a small solar panel to keep the continuous load going, not a bad way
to
> go.
>
> Jim
>
> > Seems running a generator would be simpler and cheaper.
> >
> >
>
>

Charlie Edmondson

December 15th 05, 12:13 AM

Martin Riddle

December 15th 05, 12:54 AM

It could be done, but you'll spend about $8-9 a watt with no rebates cause your not grid connected.

Vist the homepower news groups. Or www.homepower.com

You'll need a generator backup, diesel preferred.

Calculations for Autonomy, days with out sun.

Calculations for collector plate angle, for winter months.

Possibly a licensed electrician to install. Depends on local codes.

All systems are only %70-74 of their actual panel ratings, So keep this in mind. (its an efficiency thing)

And probably a large 1000's of amp hours battery bank to meet the autonomy specs.
Assuming 8hrs for lighting, 2K @ 8hrs (24v) is 666AH, usually Autonomy is 4-5 days. So your looking at 2000-3000 of AH battery
capacity. (no cheep truck deep cycles here) Plus you'll need to charge them with the PV's ;D.

Cheers

"RST Engineering" > wrote in message .. .
> After much thought and ponderance, I've come to the conclusion that to
> electrify the hangar using Pacific Gas & Electricity (PG&E -- Pigs, Goats,
> and Elephants) isn't clever. By the time you get them to hang a meter
> ($5k), trench from the power pole to the end of the row of hangars, conduit
> romex to 35 hangars at a cost somewhere around $50k ($1500 per hangar), and
> then pay the monthly electric bill, you could buy a hell of a wind/solar
> system and perch it on the (flat) hangar roof.
>
> Before I flail about gathering data, has anybody on these ngs actually
> installed a design whereby a hefty solar panel charges a hefty battery to
> run a hefty inverter? It doesn't have to be absolutely "clean" sinewave
> power as all we are running are fluorescent shop lights (about 400 watts
> worth), every now and again a small compressor, a small drill press, a small
> grinder, but none of these last few at the same time.
>
> My hit on it is that a 2 kW inverter would be more than enough to handle the
> AC side of it, and a bank of 12 volt truck batteries would work for the DC
> side of it, but there are the problems of parallelling large batteries, how
> to combine the outputs of solar cells and wind generators, and a reasonable
> source for all this stuff.
>
> There are issues around protecting the solar cells from hail, which we do
> get from time to time, battery acidic gases inside a hangar where a very
> expensive lump of aluminum is sitting for months on end, sizing the solar
> cell and wind generators, and other considerations along these lines.
>
> Comments appreciated.
>
>
> Jim
>
>

Vaughn

December 15th 05, 01:31 AM

"RST Engineering" > wrote in message
.. .

Think about a modest solar system for lighting only and a generator for the
rest. I have 100 watts of solar panels and a small charge controller that
easily runs two 60 watt-equivalent compact fluorescent lamps that have been
lighting up my yard every night for the last several years. The battery bank
for that little solar system doubles as the starting battery for my generator.
One of those pad-mounted generators you see at Home Depot could easily handle
the machine shop tools and would probably only see a few hours of use per month.

To get an idea of solar prices, try here: http://www.sunelec.com/index.html

Vaughn

Mike Rapoport

December 15th 05, 04:26 AM

The economics still aren't there for solar in most situations unless PG&E
has a high minimium monthly bill. The place to same money here in Sandpoint
is on sewer and water. The connection fees are high and the minimium bill
is about $40. One well and one leach field could serve numerous hangers.

Mike
MU-2

"RST Engineering" > wrote in message
.. .
> After much thought and ponderance, I've come to the conclusion that to
> electrify the hangar using Pacific Gas & Electricity (PG&E -- Pigs, Goats,
> and Elephants) isn't clever. By the time you get them to hang a meter
> ($5k), trench from the power pole to the end of the row of hangars,
> conduit romex to 35 hangars at a cost somewhere around $50k ($1500 per
> hangar), and then pay the monthly electric bill, you could buy a hell of a
> wind/solar system and perch it on the (flat) hangar roof.
>
> Before I flail about gathering data, has anybody on these ngs actually
> installed a design whereby a hefty solar panel charges a hefty battery to
> run a hefty inverter? It doesn't have to be absolutely "clean" sinewave
> power as all we are running are fluorescent shop lights (about 400 watts
> worth), every now and again a small compressor, a small drill press, a
> small grinder, but none of these last few at the same time.
>
> My hit on it is that a 2 kW inverter would be more than enough to handle
> the AC side of it, and a bank of 12 volt truck batteries would work for
> the DC side of it, but there are the problems of parallelling large
> batteries, how to combine the outputs of solar cells and wind generators,
> and a reasonable source for all this stuff.
>
> There are issues around protecting the solar cells from hail, which we do
> get from time to time, battery acidic gases inside a hangar where a very
> expensive lump of aluminum is sitting for months on end, sizing the solar
> cell and wind generators, and other considerations along these lines.
>
> Comments appreciated.
>
>
> Jim
>

Mike Rapoport

December 15th 05, 04:34 AM

Jim,

Check out http://www.realgoods.com/renew/index.cfm They have a store near
you and also catalog that is very informative on sustainable, off-grid
living and systems.

Mike
MU-2

"RST Engineering" > wrote in message
...
> With a small solar panel to keep the continuous load going, not a bad way
> to go.
>
> Jim
>
>> Seems running a generator would be simpler and cheaper.
>>
>>
>
>

Don Tuite

December 15th 05, 05:00 AM

On Thu, 15 Dec 2005 04:34:35 GMT, "Mike Rapoport"
> wrote:

>Jim,
>
>Check out http://www.realgoods.com/renew/index.cfm They have a store near
>you and also catalog that is very informative on sustainable, off-grid
>living and systems.
>
I've had my reservations about RG ever since they endorsed those
piezoelectric washing-machine tablets.

More than anything though, CE/UL-approved grid-connect inverters (ok
AND EU subsidies, especially in Germany) are helping to increase cell
and panel manufacturing capacity. Which is essential to driving down
cost. I think off-the-grid is fine for hangars and folks in Idaho
with acres and acres of acres, but grid-connect is where the volume
is.

Don

Nathan Young

December 15th 05, 02:35 PM

On Wed, 14 Dec 2005 15:02:56 -0800, "RST Engineering"
> wrote:

>After much thought and ponderance, I've come to the conclusion that to
>electrify the hangar using Pacific Gas & Electricity
<snip>
>My hit on it is that a 2 kW inverter would be more than enough to handle the
>AC side of it, and a bank of 12 volt truck batteries would work for the DC
>side of it, but there are the problems of parallelling large batteries, how
>to combine the outputs of solar cells and wind generators, and a reasonable
>source for all this stuff.
<snip>
>Comments appreciated.

Clever idea. Good luck with it.

Are the hangar doors electric? If so - make sure you have enough
surge current capability to get the motor started. I have a 120V /
1850W generator and it did not have enough juice to raise the door
during a power outage.

-Nathan

Ross Richardson

December 15th 05, 04:06 PM

Hey Jim,

Try looking through this.

http://www.homepower.com/

My son has provide me some literature on renewable energy and I am
convinced with some up front spending you can survive anywere without
the power grid. You may need a 5KW generator at time when the wind,
solar, etc give out.

-------------
Regards, Ross
C-172F 180HP
KSWI

RST Engineering wrote:
> After much thought and ponderance, I've come to the conclusion that to
> electrify the hangar using Pacific Gas & Electricity (PG&E -- Pigs, Goats,
> and Elephants) isn't clever. By the time you get them to hang a meter
> ($5k), trench from the power pole to the end of the row of hangars, conduit
> romex to 35 hangars at a cost somewhere around $50k ($1500 per hangar), and
> then pay the monthly electric bill, you could buy a hell of a wind/solar
> system and perch it on the (flat) hangar roof.
>
> Before I flail about gathering data, has anybody on these ngs actually
> installed a design whereby a hefty solar panel charges a hefty battery to
> run a hefty inverter? It doesn't have to be absolutely "clean" sinewave
> power as all we are running are fluorescent shop lights (about 400 watts
> worth), every now and again a small compressor, a small drill press, a small
> grinder, but none of these last few at the same time.
>
> My hit on it is that a 2 kW inverter would be more than enough to handle the
> AC side of it, and a bank of 12 volt truck batteries would work for the DC
> side of it, but there are the problems of parallelling large batteries, how
> to combine the outputs of solar cells and wind generators, and a reasonable
> source for all this stuff.
>
> There are issues around protecting the solar cells from hail, which we do
> get from time to time, battery acidic gases inside a hangar where a very
> expensive lump of aluminum is sitting for months on end, sizing the solar
> cell and wind generators, and other considerations along these lines.
>
> Comments appreciated.
>
>
> Jim
>
>

RST Engineering

December 15th 05, 04:10 PM

The hangar doors have the Armstrong opening/closing mechanism.

Jim

"Nathan Young" > wrote in message
...
> On Wed, 14 Dec 2005 15:02:56 -0800, "RST Engineering"
> > wrote:

> Clever idea. Good luck with it.
>
> Are the hangar doors electric? If so - make sure you have enough
> surge current capability to get the motor started. I have a 120V /
> 1850W generator and it did not have enough juice to raise the door
> during a power outage.
>
> -Nathan
>

Denny

December 15th 05, 05:06 PM

Hey Jim,
Check the cruising boat and trawler chat groups... THey have off the
grid down to a science..
Solar cells to keep your battery set charged and a generator for surge
loads... Better yet, is a DC alternator on your truck for charging the
batteries adn doing welding on the side.. see here
http://www.ceniehoff.com/products/altDisplay.asp?searchtype=1&volt=&=&make_name=N1602-1&keyword=

denny

Michelle P

December 15th 05, 08:48 PM

Jim,
Try alt.energy.homepower or alt.solar.photovoltaic. Lots of experts there.
Michelle

RST Engineering wrote:

>After much thought and ponderance, I've come to the conclusion that to
>electrify the hangar using Pacific Gas & Electricity (PG&E -- Pigs, Goats,
>and Elephants) isn't clever. By the time you get them to hang a meter
>($5k), trench from the power pole to the end of the row of hangars, conduit
>romex to 35 hangars at a cost somewhere around $50k ($1500 per hangar), and
>then pay the monthly electric bill, you could buy a hell of a wind/solar
>system and perch it on the (flat) hangar roof.
>
>Before I flail about gathering data, has anybody on these ngs actually
>installed a design whereby a hefty solar panel charges a hefty battery to
>run a hefty inverter? It doesn't have to be absolutely "clean" sinewave
>power as all we are running are fluorescent shop lights (about 400 watts
>worth), every now and again a small compressor, a small drill press, a small
>grinder, but none of these last few at the same time.
>
>My hit on it is that a 2 kW inverter would be more than enough to handle the
>AC side of it, and a bank of 12 volt truck batteries would work for the DC
>side of it, but there are the problems of parallelling large batteries, how
>to combine the outputs of solar cells and wind generators, and a reasonable
>source for all this stuff.
>
>There are issues around protecting the solar cells from hail, which we do
>get from time to time, battery acidic gases inside a hangar where a very
>expensive lump of aluminum is sitting for months on end, sizing the solar
>cell and wind generators, and other considerations along these lines.
>
>Comments appreciated.
>
>
>Jim
>
>
>
>

Mike Spera

December 16th 05, 12:17 AM

Try an outfit called "Real Goods". They are a bunch of old hippies who
started out with a lot of alternative energy products. They are now into
consumer goods, but I believe they still do solar. Their older catalogs
have a lot of planning information in them. At one time they were
trying to sell some older used panels that a power company offed when
they shelved a project. It was many years ago, but they may still have
some left.

Running fluorescents is a snap with solar. Any bigger load gets complex
and expensive fast.

Good Luck,
Mike

[email protected]

December 16th 05, 12:20 AM

RST Engineering wrote:
> After much thought and ponderance, I've come to the conclusion that to
> electrify the hangar using Pacific Gas & Electricity (PG&E -- Pigs, Goats,
> and Elephants) isn't clever. By the time you get them to hang a meter
> ($5k), trench from the power pole to the end of the row of hangars, conduit
> romex to 35 hangars at a cost somewhere around $50k ($1500 per hangar), and
> then pay the monthly electric bill, you could buy a hell of a wind/solar
> system and perch it on the (flat) hangar roof.

yes, thats when solar pv starts to look good.

> Before I flail about gathering data, has anybody on these ngs actually
> installed a design whereby a hefty solar panel charges a hefty battery to
> run a hefty inverter?
> It doesn't have to be absolutely "clean" sinewave
> power as all we are running are fluorescent shop lights (about 400 watts
> worth), every now and again a small compressor, a small drill press, a small
> grinder, but none of these last few at the same time.

There are 2 main invertor options, sine or modified sine, which is IRL
rectangular wave. IIRC, iron fl ballasts and motors can overheat on
MSW, so all your apps ideally want sine. However MSW is much cheaper,
and there are workarounds. Fl lights can be run at just slightly
reduced power, or heatsinks added to the ballasts, etc. Electronic
ballast lights would run happily on 150v dc. Motor driven tools would
be fine as is unless youre running them to where they already get
seriously hot, ie heavy use. There are ways round it if it proves to be
an issue.

> My hit on it is that a 2 kW inverter would be more than enough to handle the
> AC side of it, and a bank of 12 volt truck batteries would work for the DC
> side of it, but there are the problems of parallelling large batteries, how
> to combine the outputs of solar cells and wind generators, and a reasonable
> source for all this stuff.

ok, first with those powers it would make more sense to run your
battery back at apx 150v (assuming you want 110v ac) and use a simple
chopper to produce the ac. Your output will then have unregulated
V_peak and regulated constant rms. That should work for all your loads.

You should add a parallel diode across each battery cell, so that one
cell going down has little effect on system performance, and enables
everything to continue running. Ditto with the panels, there its
particularly important to have a diode across every panel when youre
running them at HT.

This avoids parallelling batteries (not that thats needed anyway), plus
reduces cost of invertor and wiring. Also it means you can supply 150v
dc to mains CFL bulbs, electronic ballasted fl lights, and anything
else that rectifies the mains, again cutting down on system cost and
improving reliability. Use a different plug/socket type for the dc
supply.

One way to shave 10-20% off power consumption would be to up your
supply frequency slightly, this would work nicely with magentic ballast
lights and brushed motors, but not induction motors. FWIW brushed
motors can run on dc anyway - but not @ 150v.

Solar pv is cheaper than wind, and has less significantly issues, so
I'd stick to solar.

> There are issues around protecting the solar cells from hail, which we do
> get from time to time, battery acidic gases inside a hangar where a very
> expensive lump of aluminum is sitting for months on end,

Battery case is vented to the outside.

> sizing the solar
> cell and wind generators, and other considerations along these lines.
>
> Comments appreciated.
>
>
> Jim

alt.solar.photovoltaic is the place to go.

Also dont overlook simple ways to cut cost. A minimal cost reflector
outside a window can be used to increase daylight levels, and delay
lighting dwitch on until later in the day, thus reducing system cost.
And of course a switchbank for your lighting will enable you to use the
lights only where theyre wanted at the time. No sense lighting the
whole place up bright when youre only working in one area.

And dont forget batteries dont last forever, you need to account for
future replacement. Beating your PG&E costs should not be difficult, as
long as its designed competently.

NT

wmbjk

December 16th 05, 12:55 AM

>On 15 Dec 2005
>RST Engineering wrote:
>> After much thought and ponderance, I've come to the conclusion that to
>> electrify the hangar using Pacific Gas & Electricity (PG&E -- Pigs, Goats,
>> and Elephants) isn't clever. By the time you get them to hang a meter
>> ($5k), trench from the power pole to the end of the row of hangars, conduit
>> romex to 35 hangars at a cost somewhere around $50k ($1500 per hangar), and
>> then pay the monthly electric bill, you could buy a hell of a wind/solar
>> system and perch it on the (flat) hangar roof.

You might start with a small bank of golf cart batteries from Sam's
Club, and a refurbished inverter/charger from here
http://www.sunelec.com/Distributors_/Trace/invacccltrace.html A Trace
SW would be best, but you'd probably be happy with a DR. Use a Honda
EU2000 for a charger to get started and as a backup later on. Add PV
as your budget allows. Excellent info on home built wind turbines here
http://www.otherpower.com/. There's no problem paralleling solar and
wind charge controllers. Include a proper system monitor like an
E-Meter or TriMetric.

Wayne

Drew Dalgleish

December 16th 05, 03:27 AM

Don Lancaster

December 16th 05, 05:36 PM

Ross Richardson wrote:
> Hey Jim,
>
> Try looking through this.
>
> http://www.homepower.com/
>
> My son has provide me some literature on renewable energy and I am
> convinced with some up front spending you can survive anywere without
> the power grid. You may need a 5KW generator at time when the wind,
> solar, etc give out.
>
>
> -------------
> Regards, Ross
> C-172F 180HP
> KSWI
>
> RST Engineering wrote:
>
>> After much thought and ponderance, I've come to the conclusion that to
>> electrify the hangar using Pacific Gas & Electricity (PG&E -- Pigs,
>> Goats, and Elephants) isn't clever. By the time you get them to hang
>> a meter ($5k), trench from the power pole to the end of the row of
>> hangars, conduit romex to 35 hangars at a cost somewhere around $50k
>> ($1500 per hangar), and then pay the monthly electric bill, you could
>> buy a hell of a wind/solar system and perch it on the (flat) hangar roof.
>>
>> Before I flail about gathering data, has anybody on these ngs actually
>> installed a design whereby a hefty solar panel charges a hefty battery
>> to run a hefty inverter? It doesn't have to be absolutely "clean"
>> sinewave power as all we are running are fluorescent shop lights
>> (about 400 watts worth), every now and again a small compressor, a
>> small drill press, a small grinder, but none of these last few at the
>> same time.
>>
>> My hit on it is that a 2 kW inverter would be more than enough to
>> handle the AC side of it, and a bank of 12 volt truck batteries would
>> work for the DC side of it, but there are the problems of parallelling
>> large batteries, how to combine the outputs of solar cells and wind
>> generators, and a reasonable source for all this stuff.
>>
>> There are issues around protecting the solar cells from hail, which we
>> do get from time to time, battery acidic gases inside a hangar where a
>> very expensive lump of aluminum is sitting for months on end, sizing
>> the solar cell and wind generators, and other considerations along
>> these lines.
>>
>> Comments appreciated.
>>
>>
>> Jim
>>

http://www.tinaja.com/glib/energfun.pdf

--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml email:

Please visit my GURU's LAIR web site at http://www.tinaja.com

Javier Henderson

December 16th 05, 06:01 PM

[email protected]

December 16th 05, 07:01 PM

Javier Henderson wrote:
> RST Engineering wrote:
> > After much thought and ponderance, I've come to the conclusion that to
> > electrify the hangar using Pacific Gas & Electricity (PG&E -- Pigs, Goats,
> > and Elephants) isn't clever. By the time you get them to hang a meter
> > ($5k), trench from the power pole to the end of the row of hangars, conduit
> > romex to 35 hangars at a cost somewhere around $50k ($1500 per hangar), and
> > then pay the monthly electric bill, you could buy a hell of a wind/solar
> > system and perch it on the (flat) hangar roof.
> >
> > Before I flail about gathering data, has anybody on these ngs actually
> > installed a design whereby a hefty solar panel charges a hefty battery to
> > run a hefty inverter? It doesn't have to be absolutely "clean" sinewave
> > power as all we are running are fluorescent shop lights (about 400 watts
> > worth), every now and again a small compressor, a small drill press, a small
> > grinder, but none of these last few at the same time.
> >
> > My hit on it is that a 2 kW inverter would be more than enough to handle the
> > AC side of it, and a bank of 12 volt truck batteries would work for the DC
> > side of it, but there are the problems of parallelling large batteries, how
> > to combine the outputs of solar cells and wind generators, and a reasonable
> > source for all this stuff.
> >
> > There are issues around protecting the solar cells from hail, which we do
> > get from time to time, battery acidic gases inside a hangar where a very
> > expensive lump of aluminum is sitting for months on end, sizing the solar
> > cell and wind generators, and other considerations along these lines.
> >
>
> Hello Jim,
>
> A good friend of mine went a bit overboard...
>
> http://www.solarwarrior.com/
>

Here's a local family that went off the grid using a combination of
solar panels and (bio)diesel generators:

http://leavingthegrid.blogspot.com/

George Ghio

December 17th 05, 01:33 PM

wrote:

>
> There are 2 main invertor options, sine or modified sine, which is IRL
> rectangular wave. IIRC, iron fl ballasts and motors can overheat on
> MSW, so all your apps ideally want sine. However MSW is much cheaper,
> and there are workarounds. Fl lights can be run at just slightly
> reduced power, or heatsinks added to the ballasts, etc. Electronic
> ballast lights would run happily on 150v dc. Motor driven tools would
> be fine as is unless youre running them to where they already get
> seriously hot, ie heavy use. There are ways round it if it proves to be
> an issue.

Small point.

Why would anybody modify a sine wave?

When people try to sell a "Modified Sine wave" inverter they are either
ignorant or shysters.

Alan Adrian

December 17th 05, 03:12 PM

No doubt you are correct....

But a "modified sine wave" inverter is a way for someone to tell you that
you are buying a device which doesn't put out a proper sine wave... rather
one which consists of an approximate sinusoidal curve made up from square
bits...

So it's not a modified sine wave, but rather a near sine wave with lots of
edges... Inferior in every way (but price) to a real sine wave inverter...

Al...

"George Ghio" > wrote in message
...
>
>
> wrote:
>
>>
>> There are 2 main invertor options, sine or modified sine, which is IRL
>> rectangular wave. IIRC, iron fl ballasts and motors can overheat on
>> MSW, so all your apps ideally want sine. However MSW is much cheaper,
>> and there are workarounds. Fl lights can be run at just slightly
>> reduced power, or heatsinks added to the ballasts, etc. Electronic
>> ballast lights would run happily on 150v dc. Motor driven tools would
>> be fine as is unless youre running them to where they already get
>> seriously hot, ie heavy use. There are ways round it if it proves to be
>> an issue.
>
> Small point.
>
> Why would anybody modify a sine wave?
>
> When people try to sell a "Modified Sine wave" inverter they are either
> ignorant or shysters.
>

Frank Bemelman

December 17th 05, 03:50 PM

"Spehro Pefhany" > schreef in bericht
...
> On Sun, 18 Dec 2005 00:33:33 +1100, the renowned George Ghio
> > wrote:
>
> >
> >
> wrote:
> >
> >>
> >> There are 2 main invertor options, sine or modified sine, which is IRL
> >> rectangular wave. IIRC, iron fl ballasts and motors can overheat on
> >> MSW, so all your apps ideally want sine. However MSW is much cheaper,
> >> and there are workarounds. Fl lights can be run at just slightly
> >> reduced power, or heatsinks added to the ballasts, etc. Electronic
> >> ballast lights would run happily on 150v dc. Motor driven tools would
> >> be fine as is unless youre running them to where they already get
> >> seriously hot, ie heavy use. There are ways round it if it proves to be
> >> an issue.
> >
> >Small point.
> >
> >Why would anybody modify a sine wave?
> >
> >When people try to sell a "Modified Sine wave" inverter they are either
> >ignorant or shysters.
>
> To paraphrase a classic George Carlin routine- "I'll tell you what
> 'modified sine wave' means-- no f*cking sine waves".

I would label the boxes with a nice star shaped
sticker "powerful harmonic sine waves".

--
Thanks, Frank.
(remove 'q' and '.invalid' when replying by email)

Spehro Pefhany

December 17th 05, 03:53 PM

On Sun, 18 Dec 2005 00:33:33 +1100, the renowned George Ghio
> wrote:

>
>
wrote:
>
>>
>> There are 2 main invertor options, sine or modified sine, which is IRL
>> rectangular wave. IIRC, iron fl ballasts and motors can overheat on
>> MSW, so all your apps ideally want sine. However MSW is much cheaper,
>> and there are workarounds. Fl lights can be run at just slightly
>> reduced power, or heatsinks added to the ballasts, etc. Electronic
>> ballast lights would run happily on 150v dc. Motor driven tools would
>> be fine as is unless youre running them to where they already get
>> seriously hot, ie heavy use. There are ways round it if it proves to be
>> an issue.
>
>Small point.
>
>Why would anybody modify a sine wave?
>
>When people try to sell a "Modified Sine wave" inverter they are either
>ignorant or shysters.

To paraphrase a classic George Carlin routine- "I'll tell you what
'modified sine wave' means-- no f*cking sine waves".

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

[email protected]

December 17th 05, 04:20 PM

Alan Adrian > wrote:

>No doubt you are correct....

No. GG is the ignorant one again. MSW is professional EE talk.

>> When people try to sell a "Modified Sine wave" inverter they are either
>> ignorant or shysters.

Nick

Steve Spence

December 17th 05, 07:55 PM

wrote:
> Alan Adrian > wrote:
>
>
>>No doubt you are correct....
>
>
> No. GG is the ignorant one again. MSW is professional EE talk.

I'd rather call it professional sales talk. It's not a modified sine
wave, it's a modified square wave to approximate a sine wave, and in
many cases, sufficiently close enough. We run our whole house on a MSW
unit. Trace's DR series inverters were MSW.

>
>
>>>When people try to sell a "Modified Sine wave" inverter they are either
>>>ignorant or shysters.

nope, just normal sales folk. unfortunately, it became an industry term.

>
>
> Nick
>

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

George Ghio

December 18th 05, 02:54 AM

No, what is being marketed is a "Modified Square Wave" inverter.

The ignorant can be forgiven.

The shyster wants you to believe that you are buying a better inverter
than it really is.

Buyer beware.

Alan Adrian wrote:
> No doubt you are correct....
>
> But a "modified sine wave" inverter is a way for someone to tell you that
> you are buying a device which doesn't put out a proper sine wave... rather
> one which consists of an approximate sinusoidal curve made up from square
> bits...
>
> So it's not a modified sine wave, but rather a near sine wave with lots of
> edges... Inferior in every way (but price) to a real sine wave inverter...
>
> Al...
>
> "George Ghio" > wrote in message
> ...
>
>>
wrote:
>>
>>
>>>There are 2 main invertor options, sine or modified sine, which is IRL
>>>rectangular wave. IIRC, iron fl ballasts and motors can overheat on
>>>MSW, so all your apps ideally want sine. However MSW is much cheaper,
>>>and there are workarounds. Fl lights can be run at just slightly
>>>reduced power, or heatsinks added to the ballasts, etc. Electronic
>>>ballast lights would run happily on 150v dc. Motor driven tools would
>>>be fine as is unless youre running them to where they already get
>>>seriously hot, ie heavy use. There are ways round it if it proves to be
>>>an issue.
>>
>>Small point.
>>
>>Why would anybody modify a sine wave?
>>
>>When people try to sell a "Modified Sine wave" inverter they are either
>>ignorant or shysters.
>>
>
>
>

George Ghio

December 18th 05, 02:57 AM

Hi Nick

MSW is a shysters sales pitch which misrepresents the product.

Sort of like someone selling bilge pumps as suitable for continuous duty.

wrote:
> Alan Adrian > wrote:
>
>
>>No doubt you are correct....
>
>
> No. GG is the ignorant one again. MSW is professional EE talk.
>
>
>>>When people try to sell a "Modified Sine wave" inverter they are either
>>>ignorant or shysters.
>
>
> Nick
>

George Ghio

December 18th 05, 03:05 AM

Steve Spence wrote:
> wrote:
>
>> Alan Adrian > wrote:
>>
>>
>>> No doubt you are correct....
>>
>>
>>
>> No. GG is the ignorant one again. MSW is professional EE talk.
>
>
> I'd rather call it professional sales talk. It's not a modified sine
> wave, it's a modified square wave to approximate a sine wave, and in
> many cases, sufficiently close enough. We run our whole house on a MSW
> unit. Trace's DR series inverters were MSW.

I have nothing against the modified sq. wave inverters.

Misrepresenting a product is lying.
>
>>
>>
>>>> When people try to sell a "Modified Sine wave" inverter they are
>>>> either ignorant or shysters.
>
>
> nope, just normal sales folk. unfortunately, it became an industry term.
>
>>
Nope, shysters or ignorant. The ignorant don't know any better and the
shyster is a lier and a thief. No point doing business with either of
them. "Modified Sq. Wave" is just that. Sine Wave is not stepped.

Both types of inverter have uses and can provide good service. But a lie
is a lie.

>>
>> Nick
>>
>
>

[email protected]

December 18th 05, 06:12 AM

Frank Bemelman wrote:
> "Spehro Pefhany" > schreef in bericht
> ...
> > On Sun, 18 Dec 2005 00:33:33 +1100, the renowned George Ghio

> > >When people try to sell a "Modified Sine wave" inverter they are either
> > >ignorant or shysters.
> >
> > To paraphrase a classic George Carlin routine- "I'll tell you what
> > 'modified sine wave' means-- no f*cking sine waves".
>
> I would label the boxes with a nice star shaped
> sticker "powerful harmonic sine waves".

ha, youre a natural :)

NT

wmbjk

December 18th 05, 02:51 PM

On Sun, 18 Dec 2005 14:05:32 +1100, George Ghio >
wrote:

>I have nothing against the modified sq. wave inverters.
>
>Misrepresenting a product is lying.

Using industry-accepted terminology to describe a product does not
constitute lying.

>Nope, shysters or ignorant. The ignorant don't know any better and the
>shyster is a lier and a thief. No point doing business with either of
>them.

No point in doing business with the ignorant? Sounds like a good idea
considering the following Ghioism....

>"Modified Sq. Wave" is just that. Sine Wave is not stepped.

<sigh> You might correct your error by listing some popular "sine"
wave inverters, and the number of steps in their "not stepped"
waveforms.

Wayne

George Ghio

December 19th 05, 05:35 AM

wmbjk wrote:
> On Sun, 18 Dec 2005 14:05:32 +1100, George Ghio >
> wrote:
>
>
>>I have nothing against the modified sq. wave inverters.
>>
>>Misrepresenting a product is lying.
>
>
> Using industry-accepted terminology to describe a product does not
> constitute lying.

When a lie becomes industry-accepted terminology then the industry is in
deep ****.
>
>
>>Nope, shysters or ignorant. The ignorant don't know any better and the
>>shyster is a lier and a thief. No point doing business with either of
>>them.
>
>
> No point in doing business with the ignorant? Sounds like a good idea
> considering the following Ghioism....
>
>
>>"Modified Sq. Wave" is just that. Sine Wave is not stepped.
>
>
> <sigh> You might correct your error by listing some popular "sine"
> wave inverters, and the number of steps in their "not stepped"
> waveforms.

Yes Mildred there really are true sine wave inverters that are not just
a sq. wave with many, many steps.

Do your own ****ing search.
>
> Wayne

wmbjk

December 19th 05, 02:34 PM

On Mon, 19 Dec 2005 16:35:16 +1100, George Ghio >
wrote:

>wmbjk wrote:
>> On Sun, 18 Dec 2005 14:05:32 +1100, George Ghio >
>> wrote:

>When a lie becomes industry-accepted terminology then the industry is in
>deep ****.

It was never a "lie" except in your ignorant vernacular. And for an
industry in "deep ****" it seems to be doing rather well overall.

>>>"Modified Sq. Wave" is just that. Sine Wave is not stepped.
>>
>>
>> <sigh> You might correct your error by listing some popular "sine"
>> wave inverters, and the number of steps in their "not stepped"
>> waveforms.
>
>Yes Mildred there really are true sine wave inverters that are not just
>a sq. wave with many, many steps.

Another unsupported claim by Mr. Hole Digger. But at least you've
admitted in weasel-speak that some <snorf> "sine" wave inverters *do*
have stepped waveforms. Would you say that they're manufactured and
sold by liars?

>Do your own ****ing search.

I take that to mean that you won't be providing any examples of sine
wave inverters with stepless waveforms. What a shocker.

Wayne

Steve Spence

December 19th 05, 03:04 PM

wmbjk wrote:
> On Mon, 19 Dec 2005 16:35:16 +1100, George Ghio >
> wrote:
>
>
>>wmbjk wrote:
>>
>>>On Sun, 18 Dec 2005 14:05:32 +1100, George Ghio >
>>>wrote:
>
>
>>When a lie becomes industry-accepted terminology then the industry is in
>>deep ****.
>
>
> It was never a "lie" except in your ignorant vernacular. And for an
> industry in "deep ****" it seems to be doing rather well overall.
>
>
>>>>"Modified Sq. Wave" is just that. Sine Wave is not stepped.
>>>
>>>
>>><sigh> You might correct your error by listing some popular "sine"
>>>wave inverters, and the number of steps in their "not stepped"
>>>waveforms.
>>
>>Yes Mildred there really are true sine wave inverters that are not just
>>a sq. wave with many, many steps.
>
>
> Another unsupported claim by Mr. Hole Digger. But at least you've
> admitted in weasel-speak that some <snorf> "sine" wave inverters *do*
> have stepped waveforms. Would you say that they're manufactured and
> sold by liars?
>
>
>>Do your own ****ing search.
>
>
> I take that to mean that you won't be providing any examples of sine
> wave inverters with stepless waveforms. What a shocker.
>
> Wayne

although I find myself in agreement with george (very scary, especially
after his recent voltage driven LED faux pas) that the moniker "Modified
Sine Wave" is a misleading term, and should be changed to "Modified
Square Wave" in order to more accurately reflect the technology, you
seemed to have gotten under his skin a bit. Congrats.

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

wmbjk

December 19th 05, 03:32 PM

On Mon, 19 Dec 2005 10:04:21 -0500, Steve Spence
> wrote:

>wmbjk wrote:
>> On Mon, 19 Dec 2005 16:35:16 +1100, George Ghio >
>> wrote:
>>
>>
>>>wmbjk wrote:
>>>
>>>>On Sun, 18 Dec 2005 14:05:32 +1100, George Ghio >
>>>>wrote:
>>
>>
>>>When a lie becomes industry-accepted terminology then the industry is in
>>>deep ****.
>>
>>
>> It was never a "lie" except in your ignorant vernacular. And for an
>> industry in "deep ****" it seems to be doing rather well overall.
>>
>>
>>>>>"Modified Sq. Wave" is just that. Sine Wave is not stepped.
>>>>
>>>>
>>>><sigh> You might correct your error by listing some popular "sine"
>>>>wave inverters, and the number of steps in their "not stepped"
>>>>waveforms.
>>>
>>>Yes Mildred there really are true sine wave inverters that are not just
>>>a sq. wave with many, many steps.
>>
>>
>> Another unsupported claim by Mr. Hole Digger. But at least you've
>> admitted in weasel-speak that some <snorf> "sine" wave inverters *do*
>> have stepped waveforms. Would you say that they're manufactured and
>> sold by liars?
>>
>>
>>>Do your own ****ing search.
>>
>>
>> I take that to mean that you won't be providing any examples of sine
>> wave inverters with stepless waveforms. What a shocker.
>>
>> Wayne
>
>although I find myself in agreement with george (very scary, especially
>after his recent voltage driven LED faux pas) that the moniker "Modified
>Sine Wave" is a misleading term, and should be changed to "Modified
>Square Wave" in order to more accurately reflect the technology,

If only he'd stopped at making that point. But Judge Ghio had to
pontificate about liars, ignorance, and shysters. He just never knows
when to shut up. Anyway, the term is unlikely to ever be changed, and
it's a pretty minor issue IMO.

> you
>seemed to have gotten under his skin a bit. Congrats.

It's sooooo easy, since he *always* defends his mistakes with more
mistakes. The topper was "never wrong mate". Now *that's* funny.
Apparently the weasel definition of "never" is "most of the time".

Wayne

[email protected]

December 19th 05, 04:30 PM

> the moniker "Modified Sine Wave" is a misleading term, and should be
> changed to "Modified Square Wave"

I would prefer "stepped sine wave". But I can accept the term "modified
sine wave" as marketing speak that has been on lots of UPS boxes for 20
years. (UPS itself being inaccurate for a standby power source.)

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5

John Larkin

December 19th 05, 04:51 PM

On Mon, 19 Dec 2005 16:30:20 +0000 (UTC),
wrote:

>> the moniker "Modified Sine Wave" is a misleading term, and should be
>> changed to "Modified Square Wave"
>
>I would prefer "stepped sine wave". But I can accept the term "modified
>sine wave" as marketing speak that has been on lots of UPS boxes for 20
>years. (UPS itself being inaccurate for a standby power source.)

A chirped-frequency, nanosecond-wide, random-amplitude pulse train is
a modified sine wave.

John

RST Engineering

December 19th 05, 06:49 PM

Plonk!

Jim

"George Ghio" > wrote in message
...
>
> Do your own ****ing search.

Rich Grise

December 19th 05, 07:26 PM

On Mon, 19 Dec 2005 08:51:30 -0800, John Larkin wrote:
> wrote:
>
>>> the moniker "Modified Sine Wave" is a misleading term, and should be
>>> changed to "Modified Square Wave"
>>
>>I would prefer "stepped sine wave". But I can accept the term "modified
>>sine wave" as marketing speak that has been on lots of UPS boxes for 20
>>years. (UPS itself being inaccurate for a standby power source.)
>
> A chirped-frequency, nanosecond-wide, random-amplitude pulse train is
> a modified sine wave.
>
> John

;-)

Thanks!
Rich

[email protected]

December 19th 05, 08:50 PM

In alt.solar.photovoltaic John Larkin > wrote:

> A chirped-frequency, nanosecond-wide, random-amplitude pulse train is
> a modified sine wave.

I will accept that definition as offered.
Does that preclude having any other valid definitions?

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5

Steve Spence

December 20th 05, 03:07 AM

wrote:
>>the moniker "Modified Sine Wave" is a misleading term, and should be
>>changed to "Modified Square Wave"
>
>
> I would prefer "stepped sine wave". But I can accept the term "modified
> sine wave" as marketing speak that has been on lots of UPS boxes for 20
> years. (UPS itself being inaccurate for a standby power source.)
>

I believe "stepped sine wave" to be an oxymoron. UPS (uninterruptable
power supply) isn't so wrong, as from the computer's POV, the power
never was interrupted. Of course, we know the difference between
"online" and "backup".

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

philkryder

December 20th 05, 07:51 AM

Steve - How many equal "steps" are necessary for the MSW inverter to be
a sufficiently close approximation to a "rotary" sine wave?

Roger

December 20th 05, 10:01 AM

On Wed, 14 Dec 2005 15:33:27 -0800, "RST Engineering"
> wrote:

>With a small solar panel to keep the continuous load going, not a bad way to
>go.

I recently talked to a guy down in Florida, where the sun is more
direct and shows up much more often than here in Michigan. He said a
decent solar powered system to run a medium size (what's medium size?)
house was about $20,000 for the installation.

You can plan on replacing lead acid batteries about every 3 years or
so. Nickel Metal Hydride (NiMH) are about the same, except the car
manufacturers are claiming much longer life using computer controlled
charging. Time will tell.

Solar panels are still darned expensive. Using a mix of solar and
wind you charge different banks with solid state regulators and
switches.

The inverter only needs to be sized large enough to handle the
expected load. As long as you are not running electronics the wave
form is not much of a problem...except... for radio interference. Some
switching supplies (which are very efficient) are very noisy.

You can get one whale of a nice liquid cooled Honda Generator that
runs quiet and will supply enough juice to run a good size house
continuously. I have a 9,500 Watt continuous generator that will
power our whole house on about a gallon an hour. Maybe a tad less. It
burns way less than the little 4400 watt portable I used to have and
it is *much* quieter. Unfortunately I spend $1,200 and it's not a
quiet Honda. OTOH fortunately I purchased it from Lowe's a couple of
weeks after the Y2K fiasco. People had cleaned them out and were then
returning the "unused" generators. They finally said "No more". Some
of those "unused" generators looked like they'd been sitting out in
salt spray for a couple of months. Mine was more than 50% off and it
was still in the box. It was one of the few that they hadn't sold.
They had a lot of them cheap for a few months. The one store here in
town must have had 50 or more although most of them weren't 9500 watt
units.

Currently Home Depot has some 15KW "home generators" complete with
transfer switch that will do an automatic transfer, as well as
exercising once a week. They'll run on Gas, Natural Gas, or LP gas
and come in a small enclosure that looks like a whole house air
conditioner. I'd like to try one of those, but my wife says I spent
more than enough on what we have and we can drag that heavy cable out
to the generator shed for a lot less than $2,200 <:-))

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

>
>Jim
>
>> Seems running a generator would be simpler and cheaper.
>>
>>
>
Roger

Roger

December 20th 05, 10:04 AM

On Thu, 15 Dec 2005 05:00:15 GMT, Don Tuite
> wrote:

>On Thu, 15 Dec 2005 04:34:35 GMT, "Mike Rapoport"
> wrote:
>
>>Jim,
>>
>>Check out http://www.realgoods.com/renew/index.cfm They have a store near
>>you and also catalog that is very informative on sustainable, off-grid
>>living and systems.
>>
>I've had my reservations about RG ever since they endorsed those
>piezoelectric washing-machine tablets.
>
>More than anything though, CE/UL-approved grid-connect inverters (ok
>AND EU subsidies, especially in Germany) are helping to increase cell
>and panel manufacturing capacity. Which is essential to driving down

There have been several "breakthroughs" that could *potentially* cut
the cost of the solar cells to less than half of current and at the
same time increase the efficiency by a substantial margin.

There were a lot of weasel words in the press release so ... who
knows. IF, how soon, and how much.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
>cost. I think off-the-grid is fine for hangars and folks in Idaho
>with acres and acres of acres, but grid-connect is where the volume
>is.
>
>Don

George Ghio

December 20th 05, 12:02 PM

wmbjk wrote:

> I take that to mean that you won't be providing any examples of sine
> wave inverters with stepless waveforms. What a shocker.
>
> Wayne

Take it to mean that you can't prove that true sine wave inverters don't
exist.

Modified Square Wave inverters = True

Modified Sine Wave inverters = False

Ron Rosenfeld

December 20th 05, 12:55 PM

On Wed, 14 Dec 2005 15:02:56 -0800, "RST Engineering"
> wrote:

>After much thought and ponderance, I've come to the conclusion that to
>electrify the hangar using Pacific Gas & Electricity (PG&E -- Pigs, Goats,
>and Elephants) isn't clever. By the time you get them to hang a meter
>($5k), trench from the power pole to the end of the row of hangars, conduit
>romex to 35 hangars at a cost somewhere around $50k ($1500 per hangar), and
>then pay the monthly electric bill, you could buy a hell of a wind/solar
>system and perch it on the (flat) hangar roof.
>
>Before I flail about gathering data, has anybody on these ngs actually
>installed a design whereby a hefty solar panel charges a hefty battery to
>run a hefty inverter? It doesn't have to be absolutely "clean" sinewave
>power as all we are running are fluorescent shop lights (about 400 watts
>worth), every now and again a small compressor, a small drill press, a small
>grinder, but none of these last few at the same time.
>
>My hit on it is that a 2 kW inverter would be more than enough to handle the
>AC side of it, and a bank of 12 volt truck batteries would work for the DC
>side of it, but there are the problems of parallelling large batteries, how
>to combine the outputs of solar cells and wind generators, and a reasonable
>source for all this stuff.
>
>There are issues around protecting the solar cells from hail, which we do
>get from time to time, battery acidic gases inside a hangar where a very
>expensive lump of aluminum is sitting for months on end, sizing the solar
>cell and wind generators, and other considerations along these lines.
>
>Comments appreciated.
>
>
>Jim
>

Jim,

As one who lives "off-the-grid" in eastern Maine, (and for similar reasons,
I might add -- excess costs to run power here), perhaps I can be of some
assistance. We use both wind and solar to power our home, and also have a
backup generator. The problems of coordinating all these things has been
solved with readily available technology. As has all of the other issues
you mentioned.

In order to make an intelligent decision and design an economical system,
your very first step has to be to estimate your electricity usage as
accurately as possible. In addition to adding up your daily consumption in
kWh or amp-hours, you also have to consider peak loads. And, especially
since you may be using a compressor, you will also have to consider the
startup surge -- with a compressor this may be five to ten times the
running amps. That information should be decipherable from the motor face
plate.

The next step is to assess your solar resource, and there is information on
the web available for that. Being at an airport, my advice is to forget
about wind. You need to have a wind turbine on a tower high enough to get
out of turbulent air, in order to make it worthwhile. The required height
would encroach upon the FAA mandated clear zones.

I'd be happy to help if you like.

Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

[email protected]

December 20th 05, 03:16 PM

In alt.solar.photovoltaic Steve Spence > wrote:
> I believe "stepped sine wave" to be an oxymoron.

I (obviously) don't agree with that. Gotta call it something. It's not a
sine wave, but if you squint at the oscilloscope a little, it looks more
like a sine wave than a square wave.

> UPS (uninterruptable power supply) isn't so wrong, as from the computer's
> POV, the power never was interrupted.

Ah, from a particular Point of View... if that's the criterion, then the
square/modified/lumpy/sine wave is a sine wave for most applications.

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5

Steve Spence

December 20th 05, 03:28 PM

philkryder wrote:
> Steve - How many equal "steps" are necessary for the MSW inverter to be
> a sufficiently close approximation to a "rotary" sine wave?
>

That depends on what you are driving. A laser printer requires closer
representation than a computer. The manufacturer of a particular load
could tell you that information. The old test of whether something was
sine or some version of square was a lamp dimmer. On a square wave unit
the light goes full bright. We have a touch lamp that will not change
state on MSW, but will on generator.

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

Rich Grise

December 20th 05, 04:05 PM

On Mon, 19 Dec 2005 23:51:48 -0800, philkryder wrote:

> Steve - How many equal "steps" are necessary for the MSW inverter to be
> a sufficiently close approximation to a "rotary" sine wave?

It depends how you count "steps". I once worked with an inverter that
used two, count'em, two, output transformers, each driven by a plain
vanilla square wave, but they were in series, and the regulation
took place by controlling the phase of the two square waves - 120
times a second, the two secondaries flipped from "buck" to "boost".
The output waveform was essentially a positive pulse, then zero, then
a negative pulse, then zero, then another positive pulse, and so on.

It ran everything we plugged into it, even an induction motor bench
grinder. Lamps are trivial, and series motors, like a hand drill,
don't care.

We didn't plug a computer into it, however, or anything with an SMPS,
so I guess my recommendation would be to check the spec on what it
is you're plugging into it.

Good Luck!
Rich

RST Engineering $jw$

December 20th 05, 06:29 PM

It seems as though we are trying to build a cathedral foundation to hold an
outhouse. It isn't like I'm LIVING in the hangar, nor am I there working
all day every day. Sure, lights when you are elbow deep inside an engine
are nice, but hardly bleeding edge solar design. What? Ten fluorescent
fixtures with 80 watts of bulbs each? A drop cord with another 20 watt
fluorescent bulb? Perhaps a hand drill twice a day WHEN you are working in
the hangar?

As to the compressor, drill press, grinder etc., a gas generator for the few
times a month you need them is quite in order and certainly less expensive
in both the short and long term than gearing up for 100% solar for the
peaks. And, if you design the system correctly, letting the gas generator
run for an hour every time you fire up and letting the batteries take a full
charge from an inexpensive battery charger can add to the output of the
solar system.

I've done a little digging and it seems that Great Plains has the best
pricing on solar panels. Harbor Freight has a little better pricing, but I
need something that I can reliably get month in and month out (I'm the
guinea pig for about 50 hangars) and I can never rely on Harbor Freight to
have what I need when I need it.

My best guess after doing a little educated digging is that I can come up
with a system I can live with for a little over 1 AMU.

(For those of you not on the aviation newsgroups, an AMU is a measure of
money used to disguise the true cost of airplane ownership from other ...
ummm ... family members who might think that clothes, food, and other
nonessentials take priority over flying. 1 AMU = $1000US.)

Jim

> In order to make an intelligent decision and design an economical system,
> your very first step has to be to estimate your electricity usage as
> accurately as possible. In addition to adding up your daily consumption
> in
> kWh or amp-hours, you also have to consider peak loads. And, especially
> since you may be using a compressor, you will also have to consider the
> startup surge -- with a compressor this may be five to ten times the
> running amps. That information should be decipherable from the motor face
> plate.

Rich Grise

December 20th 05, 06:50 PM

On Tue, 20 Dec 2005 10:29:12 -0800, RST Engineering (jw) wrote:

> My best guess after doing a little educated digging is that I can come
> up with a system I can live with for a little over 1 AMU.
>
> (For those of you not on the aviation newsgroups, an AMU is a measure of
> money used to disguise the true cost of airplane ownership from other
> ... ummm ... family members who might think that clothes, food, and
> other nonessentials take priority over flying. 1 AMU = $1000US.)
>

"Aircraft Monetary Unit?"

I've heard that a boat is a hole in the water lined with wood, into
which one pours money. ;-)

Do airplane people have a similar saying? I have only a little bit of
experience with airplanes - I logged 4 hours in a Cessna 150 before the
local flight school got shut down because of fuel considerations, and
I've sat in a DC-9 simulator, and had a simulated airplane ride where
I drove, but I've never gotten into any of the cameraderie, like one
would do as a skydiver.

Yeah, that's it - the best experiences I've ever had with airplanes
has been either abusing them or jumping out of them. ;-P

But, do airplane guys use the term "money hole" like boat and house
owners?

You can't "pour" anything _up_, you know, albeit I have heard that
humans were created by water to transport itself uphill. ;-)

Cheers!
Rich

Peter R.

December 20th 05, 06:54 PM

Rich Grise > wrote:

> You can't "pour" anything _up_, you know, albeit I have heard that
> humans were created by water to transport itself uphill. ;-)

How about suck, as in "an airplane is a rather small hole in the sky made
of aluminum or cloth and wood that sucks the money right out of the owner?"

--
Peter

Ray Andraka

December 20th 05, 07:25 PM

Rich Grise wrote:

> But, do airplane guys use the term "money hole" like boat and house
> owners?
>

>
We drill expensive holes in the sky

RST Engineering $jw$

December 20th 05, 07:59 PM

Boring $100 holes in the sky ... going fifty miles for a $100 hamburger ...
standing in front of a fan tearing up $100 bills ... dozens more.

Jim

"Rich Grise" > wrote in message
t...

> I've heard that a boat is a hole in the water lined with wood, into
> which one pours money. ;-)
>
> Do airplane people have a similar saying?

Ron Rosenfeld

December 20th 05, 08:50 PM

On Tue, 20 Dec 2005 10:29:12 -0800, "RST Engineering $jw$"
> wrote:

>It seems as though we are trying to build a cathedral foundation to hold an
>outhouse. It isn't like I'm LIVING in the hangar, nor am I there working
>all day every day. Sure, lights when you are elbow deep inside an engine
>are nice, but hardly bleeding edge solar design. What? Ten fluorescent
>fixtures with 80 watts of bulbs each? A drop cord with another 20 watt
>fluorescent bulb? Perhaps a hand drill twice a day WHEN you are working in
>the hangar?

It's not a matter of building a cathedral foundation, but rather trying to
design the least expensive foundation.

But I guess if you're going to light 35 hangars with ten fluorescent
fixtures that are on for a few minutes each day, you won't need much.

>
>As to the compressor, drill press, grinder etc., a gas generator for the few
>times a month you need them is quite in order and certainly less expensive
>in both the short and long term than gearing up for 100% solar for the
>peaks.

Very reasonable, and what I would suggest depending on how much the surge
is. Of course, that means you'll have to have wiring so that those items
will plug directly into the generator, rather than going through the
inverter.

>And, if you design the system correctly, letting the gas generator
>run for an hour every time you fire up and letting the batteries take a full
>charge from an inexpensive battery charger can add to the output of the
>solar system.

It is extremely inefficient to bring the batteries up to full charge using
the gas generator. Batteries charge more slowly as they approach full
charge. Better get a reliable generator, then.

>

>I've done a little digging and it seems that Great Plains has the best
>pricing on solar panels. Harbor Freight has a little better pricing, but I
>need something that I can reliably get month in and month out (I'm the
>guinea pig for about 50 hangars) and I can never rely on Harbor Freight to
>have what I need when I need it.
>
>My best guess after doing a little educated digging is that I can come up
>with a system I can live with for a little over 1 AMU.

Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

daestrom

December 20th 05, 11:33 PM

"philkryder" > wrote in message
oups.com...
> Steve - How many equal "steps" are necessary for the MSW inverter to be
> a sufficiently close approximation to a "rotary" sine wave?
>

Careful. Even true 'rotary' generators don't always put out a true sine
wave.

Even the very, very large commercial generators used in power plants, don't
put out a 'pure' sine wave. The number of stator slots and rotor geometry
cause a small amount of harmonics. The exact connections of windings is
often used to help improve the fundamental and minimize some of the higher
harmonics (6th, 9th and 11th are some of the more troubling ones).

After it passes through several transformers, getting to the substation,
most of the harmonics have been filtered out by the characteristics of the
transformers.

So the question, as usual, boils down to 'how good, is good enough?'

daestrom

[email protected]

December 20th 05, 11:57 PM

I've heard that a boat is a hole in the water lined with wood, into
which one pours money. ;-)

Do airplane people have a similar saying?

An Airplane is a large mobile fan into which the owner is obliged to
throw handfuls of money (to watch it blow away).

David Johnson

SolarFlare

December 21st 05, 12:28 AM

Modified Semantic Wave is correct.

"George Ghio" > wrote in message
...
>
>
> wmbjk wrote:
>
> > I take that to mean that you won't be providing any
examples of sine
> > wave inverters with stepless waveforms. What a
shocker.
> >
> > Wayne
>
> Take it to mean that you can't prove that true sine
wave inverters don't
> exist.
>
> Modified Square Wave inverters = True
>
> Modified Sine Wave inverters = False
>

SolarFlare

December 21st 05, 12:44 AM

We previously went through this crap with CD players.
The sampling frequency was chosen to be 44.1 kHz, well
beyond the range of human hearing. No filtering would
be needed.

Except for one thing...when they played the CD back
unfiltered, people would find their tweeters melting
for some weird reason....44.1kHz! at huge powers!

Out came the drawing board and complex analogue (and
expensive) filters were designed until one day some
smart engineer discovered they could double the freq.
in a computer and put out 88.2 kHz sampling noise and
use a less efficient and less expensive filter.

Well, the audio hype that came out then was "2 times
oversampling" followed by 4x, 8x, 16x & 32x
"oversampling". Shister and ignorant marketing people
explained this as "reading the CD 16 times repeatedly
and eliminating the digital errors" "You can eliminate
scratches with this"

In reality the "oversampling" technique was the
development of a digital filter that made the analogue
filter into a simple capacitor to eliminate the
sampling noise.

Any square wave can be filtered enough to produce a
pure sine wave. The trick is the cost. Huge core
inductors and capacitors to handle and smooth out big
quantities of power cost money to design and money to
produce. Not to mention the sheer weight of the beasts.

Multistep waveforms can be filtered much easier. This
is analogous the "oversampling" technique used in CD
players of years past. Digital filtering is much easier
and cheaper than the equivalent analogue filtering.
It's not like an inverter, these days, doesn't have a
computer chip inside then anyway.

How little distortion do you need anyway? Most of it
can be accomplished inside the computer and then just
amplified to useful power levels. At a cost, of course,
and a marketing tool for more money...always.

"daestrom" > wrote in
message
...
>
> "philkryder" > wrote in message
>
oups.com...
> > Steve - How many equal "steps" are necessary for
the MSW inverter to be
> > a sufficiently close approximation to a "rotary"
sine wave?
> >
>
> Careful. Even true 'rotary' generators don't always
put out a true sine
> wave.
>
> Even the very, very large commercial generators used
in power plants, don't
> put out a 'pure' sine wave. The number of stator
slots and rotor geometry
> cause a small amount of harmonics. The exact
connections of windings is
> often used to help improve the fundamental and
minimize some of the higher
> harmonics (6th, 9th and 11th are some of the more
troubling ones).
>
> After it passes through several transformers, getting
to the substation,
> most of the harmonics have been filtered out by the
characteristics of the
> transformers.
>
> So the question, as usual, boils down to 'how good,
is good enough?'
>
> daestrom
>
>

George Ghio

December 21st 05, 04:54 AM

Tell us why anyone would modify a sine wave.

SolarFlare wrote:
> Modified Semantic Wave is correct.
>
> "George Ghio" > wrote in message
> ...
>
>>
>>wmbjk wrote:
>>
>>
>>>I take that to mean that you won't be providing any
>
> examples of sine
>
>>>wave inverters with stepless waveforms. What a
>
> shocker.
>
>>>Wayne
>>
>>Take it to mean that you can't prove that true sine
>
> wave inverters don't
>
>>exist.
>>
>>Modified Square Wave inverters = True
>>
>>Modified Sine Wave inverters = False
>>
>
>
>

philkryder

December 21st 05, 06:50 AM

"....We have a touch lamp that will not change
state on MSW, but will on generator"

Do you know if these new smaller Inverter style generators are a close
enough approximation for things like the laser printer?

Just how good are the "sine" like waves on them?

I thought someone was going to put a 'scope on one...

philkryder

December 21st 05, 07:00 AM

"....It depends how you count "steps"."

Indeed.

I suppose something like "the number of distinct voltage changes per
cycle" might be a good first approximation of something to call steps
and to count.

In your example I would count something like "3" or maybe "2" or "4" -
I always have trouble with boundary conditions...

In any case, it seems that the device you had was effective.
And the only thing I could imagine as having fewer steps would be a
similar device that didn't have the pause at zero...

And yet it was effective -
I wonder if it would have worked with the light dimmer mentioned
above...

[email protected]

December 21st 05, 07:35 AM

Steve Spence wrote:
> philkryder wrote:
> > Steve - How many equal "steps" are necessary for the MSW inverter to be
> > a sufficiently close approximation to a "rotary" sine wave?
> >
>
> That depends on what you are driving. A laser printer requires closer
> representation than a computer. The manufacturer of a particular load
> could tell you that information. The old test of whether something was
> sine or some version of square was a lamp dimmer. On a square wave unit
> the light goes full bright. We have a touch lamp that will not change
> state on MSW, but will on generator.

A lot of ac loads are quite happy on dc. Almost anything that rectifies
the mains waveform will run fine on dc of V_mains x 1.414.

NT

[email protected]

December 21st 05, 07:37 AM

[email protected]

December 21st 05, 01:34 PM

George Ghio > wrote:

>Tell us why anyone would modify a sine wave.

It's called "engineering," George.

Nick

Matt Whiting

December 21st 05, 02:29 PM

George Ghio wrote:

> Tell us why anyone would modify a sine wave.

To vary the power delivered to a load. Chopping off part of a sine wave
cycle is a standard means of power control.

Matt

Keith Williams

December 21st 05, 03:10 PM

In article >,
says...
> We previously went through this crap with CD players.
> The sampling frequency was chosen to be 44.1 kHz, well
> beyond the range of human hearing. No filtering would
> be needed.

Your story is ready for Snopes (sounds good, but less than the
truth). To get to a 20kHz bandwidth the signal must be sampled at
greater than 40kHz (see Nyquist). If *everything* above the
nyquist limit isn't filtered these artifacts will be aliased.
Given that most engineer's junkbox doesn't contain perfect filters,
2kHz is left for the filter, thus a sampling rate of 44.1kHz.
T'was a trade-off of device complexity and data storage (running
time).

> Except for one thing...when they played the CD back
> unfiltered, people would find their tweeters melting
> for some weird reason....44.1kHz! at huge powers!

BS. Were it unfiltered aliasing would make the CD sound terrible.
The filter has to be in there for any sampled system. They didn't
"all of a sudden" figure out that they needed a filter.

> Out came the drawing board and complex analogue (and
> expensive) filters were designed until one day some
> smart engineer discovered they could double the freq.
> in a computer and put out 88.2 kHz sampling noise and
> use a less efficient and less expensive filter.

Less expensive filter because there is more headroom.

<snip>

--
Keith

Rich Grise

December 21st 05, 03:48 PM

On Tue, 20 Dec 2005 23:00:43 -0800, philkryder wrote:

> "....It depends how you count "steps"."
>
> Indeed.
>
> I suppose something like "the number of distinct voltage changes per
> cycle" might be a good first approximation of something to call steps
> and to count.
>
> In your example I would count something like "3" or maybe "2" or "4" -
> I always have trouble with boundary conditions...

Heh. Programmers run into this all of the time - it's called "the
fencepost effect". If you have a 100' fence, and there's a post
every 10', how many posts do you need?

Or this one: Imagine a short staircase, say to a "sunken living
room" or some such, of 3 steps:

------------
|
-----
|
-----
|
---------------------------

Now, if you had three apples, you'd be able to count them, 1, 2, 3, and
point at the middle one.

OK, now go up those three steps, counting along, and point at the middle
one. Then go down, counting again, and _now_ point at the middle one.

Isn't that cute? ;-)

> In any case, it seems that the device you had was effective.
> And the only thing I could imagine as having fewer steps would be a
> similar device that didn't have the pause at zero...
>
> And yet it was effective -
> I wonder if it would have worked with the light dimmer mentioned
> above...

I think very probably not very well, if at all, based on what others have
said.

But, if you're on an inverter already, I think there'd be a more efficient
kind of light dimmer that you could find, maybe that runs off the battery
voltage. Or sync up your triac or SCR dimmer to the inverter itself -
hmmmm.... (this one had a sync in/out so that they could be paralleled.)

Thanks!
Rich

Rich Grise

December 21st 05, 03:50 PM

On Tue, 20 Dec 2005 23:35:15 -0800, meow2222 wrote:

> Steve Spence wrote:
>> philkryder wrote:
>> > Steve - How many equal "steps" are necessary for the MSW inverter to be
>> > a sufficiently close approximation to a "rotary" sine wave?
>> >
>>
>> That depends on what you are driving. A laser printer requires closer
>> representation than a computer. The manufacturer of a particular load
>> could tell you that information. The old test of whether something was
>> sine or some version of square was a lamp dimmer. On a square wave unit
>> the light goes full bright. We have a touch lamp that will not change
>> state on MSW, but will on generator.
>
> A lot of ac loads are quite happy on dc. Almost anything that rectifies
> the mains waveform will run fine on dc of V_mains x 1.414.
>
> NT

Well, don't plug a 120VAC wall wart into 170VDC!

Or should we alert the Darwin committee? ;-)

Thanks!
Rich

[email protected]

December 21st 05, 06:40 PM

wrote....

"A lot of ac loads are quite happy on dc. Almost anything that
rectifies
the mains waveform will run fine on dc of V_mains x 1.414. "

....unless there is a transformer at the input to the power supply. Only
thing that'll happen then is the transformer might get hot.

Randy

Steve Spence

December 21st 05, 07:06 PM

philkryder wrote:
> "....We have a touch lamp that will not change
> state on MSW, but will on generator"
>
> Do you know if these new smaller Inverter style generators are a close
> enough approximation for things like the laser printer?
>
> Just how good are the "sine" like waves on them?
>
> I thought someone was going to put a 'scope on one...
>

I don't have one (inverter/generator) to test. If it's a SW then yes, it
will work. The HONDA EM50is claims to be a sine wave unit.

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

Steve Spence

December 21st 05, 07:07 PM

wrote:
> Steve Spence wrote:
>
>>philkryder wrote:
>>
>>>Steve - How many equal "steps" are necessary for the MSW inverter to be
>>>a sufficiently close approximation to a "rotary" sine wave?
>>>
>>
>>That depends on what you are driving. A laser printer requires closer
>>representation than a computer. The manufacturer of a particular load
>>could tell you that information. The old test of whether something was
>>sine or some version of square was a lamp dimmer. On a square wave unit
>>the light goes full bright. We have a touch lamp that will not change
>>state on MSW, but will on generator.
>
>
> A lot of ac loads are quite happy on dc. Almost anything that rectifies
> the mains waveform will run fine on dc of V_mains x 1.414.
>
> NT
>

My fridge and well pump are not among these devices.

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

Steve Spence

December 21st 05, 07:09 PM

wrote:
> George Ghio > wrote:
>
>
>>Tell us why anyone would modify a sine wave.
>
>
> It's called "engineering," George.
>
> Nick
>

Really... Wouldn't they rather modify a square wave to approximate a
sine wave? What would be the point of modifying a sine wave, when a sine
wave (or close approximation) is the required result?

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

Rich Grise

December 21st 05, 11:16 PM

On Wed, 21 Dec 2005 14:06:05 -0500, Steve Spence wrote:

> philkryder wrote:
>> "....We have a touch lamp that will not change
>> state on MSW, but will on generator"
>>
>> Do you know if these new smaller Inverter style generators are a close
>> enough approximation for things like the laser printer?
>>
>> Just how good are the "sine" like waves on them?
>>
>> I thought someone was going to put a 'scope on one...
>>
>
> I don't have one (inverter/generator) to test. If it's a SW then yes, it
> will work. The HONDA EM50is claims to be a sine wave unit.

It seems pretty obvious that a mechanical generator should put out a
relatively pure sine wave - it's just this big rotating magnetic field and
a couple of coils, after all. :-)

As a matter of fact, it's a little hard for me to visualize how someone
would make anything _other than_ a plain vanilla sine wave using just
a rotating magnet and a coil.

Thanks!
Rich

Rich Grise

December 21st 05, 11:25 PM

On Wed, 21 Dec 2005 14:09:10 -0500, Steve Spence wrote:

> wrote:
>> George Ghio > wrote:
>>
>>
>>>Tell us why anyone would modify a sine wave.
>>
>>
>> It's called "engineering," George.
>>
>> Nick
>>
>
> Really... Wouldn't they rather modify a square wave to approximate a
> sine wave? What would be the point of modifying a sine wave, when a sine
> wave (or close approximation) is the required result?

I hope you're not serious here.

They don't make a sine wave and modify it, they make a rectangular
wave and call it a "modified sine wave" because it passes enough tests
for harmonics and crap that it will run most stuff, and they can get
away with it. ;-)

Anybody wanna do an FFT of various duty-cycle waveforms, and give us real
THD information, and how that relates to power factor, and etc, and etc,
and etc?

The one inverter I've ever had my hands on the guts of made a waveform
like this:

---- ---- ----
| | | | | |
- - - - - -
| | | | | etc.
- ---- ----

And the regulator was just based on an ordinary rectifier - they didn't
care about RMS, or it was scaled to get "close enough".

But I do wonder, what does the harmonic content really do when you vary
the duty cycle?

Some years ago, in the USAF, I saw some pulses on a spectrum analyzer,
and they had some really pretty envelopes. :-)

Thanks,
Rich

Steve Spence

December 22nd 05, 02:29 AM

Rich Grise wrote:
> On Wed, 21 Dec 2005 14:06:05 -0500, Steve Spence wrote:
>
>
>>philkryder wrote:
>>
>>>"....We have a touch lamp that will not change
>>>state on MSW, but will on generator"
>>>
>>>Do you know if these new smaller Inverter style generators are a close
>>>enough approximation for things like the laser printer?
>>>
>>>Just how good are the "sine" like waves on them?
>>>
>>>I thought someone was going to put a 'scope on one...
>>>
>>
>>I don't have one (inverter/generator) to test. If it's a SW then yes, it
>>will work. The HONDA EM50is claims to be a sine wave unit.
>
>
> It seems pretty obvious that a mechanical generator should put out a
> relatively pure sine wave - it's just this big rotating magnetic field and
> a couple of coils, after all. :-)
>
> As a matter of fact, it's a little hard for me to visualize how someone
> would make anything _other than_ a plain vanilla sine wave using just
> a rotating magnet and a coil.
>
> Thanks!
> Rich
>
>

Inverter units do not provide mechanically driven electrical output to
the load, they run it through an inverter for frequency and voltage control.

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

Steve Spence

December 22nd 05, 02:33 AM

Rich Grise wrote:
> On Wed, 21 Dec 2005 14:09:10 -0500, Steve Spence wrote:
>
>
wrote:
>>
>>>George Ghio > wrote:
>>>
>>>
>>>
>>>>Tell us why anyone would modify a sine wave.
>>>
>>>
>>>It's called "engineering," George.
>>>
>>>Nick
>>>
>>
>>Really... Wouldn't they rather modify a square wave to approximate a
>>sine wave? What would be the point of modifying a sine wave, when a sine
>>wave (or close approximation) is the required result?
>
>
> I hope you're not serious here.
>
> They don't make a sine wave and modify it, they make a rectangular
> wave and call it a "modified sine wave" because it passes enough tests
> for harmonics and crap that it will run most stuff, and they can get
> away with it. ;-)
>
> Anybody wanna do an FFT of various duty-cycle waveforms, and give us real
> THD information, and how that relates to power factor, and etc, and etc,
> and etc?
>
> The one inverter I've ever had my hands on the guts of made a waveform
> like this:
>
> ---- ---- ----
> | | | | | |
> - - - - - -
> | | | | | etc.
> - ---- ----
>
> And the regulator was just based on an ordinary rectifier - they didn't
> care about RMS, or it was scaled to get "close enough".
>
> But I do wonder, what does the harmonic content really do when you vary
> the duty cycle?
>
> Some years ago, in the USAF, I saw some pulses on a spectrum analyzer,
> and they had some really pretty envelopes. :-)
>
> Thanks,
> Rich
>

That's my point. There are modified square wave inverters (marketed as
Modified Sine Wave), and there are "Sine Wave" inverters, which are
really MSW's with such fine steps that finicky equipment can't tell the
difference. There are a few folks on this group trying to justify the
"Modified Sine Wave" sales moniker but there is no logic to it. Folks
who should know better, but can't find it easy to "agree" with george
even for a moment. It even kills me to do it, but hey, he has a point
for once.

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

Roger

December 22nd 05, 02:47 AM

On Wed, 21 Dec 2005 23:25:58 GMT, Rich Grise >
wrote:

>On Wed, 21 Dec 2005 14:09:10 -0500, Steve Spence wrote:
>
>> wrote:
>>> George Ghio > wrote:
>>>
>>>
>>>>Tell us why anyone would modify a sine wave.
>>>
>>>
>>> It's called "engineering," George.
>>>
>>> Nick
>>>
>>
>> Really... Wouldn't they rather modify a square wave to approximate a
>> sine wave? What would be the point of modifying a sine wave, when a sine
>> wave (or close approximation) is the required result?

I only am posting this back to RAO as it's the only NG I receive out
of the list.

>
>I hope you're not serious here.
>
>They don't make a sine wave and modify it, they make a rectangular
>wave and call it a "modified sine wave" because it passes enough tests
>for harmonics and crap that it will run most stuff, and they can get
>away with it. ;-)

Switching supplies are very efficient. Unfortunately things making sin
waves from DC are not. The faster you can turn the transistors on and
off the less heat and more power you can get out of a still smaller,
lighter, and *cheaper* power supply, or inverter.

Without digging too deep, a square wave contains an almost infinite
frequency range on the rise and fall times. Most likely many
thousands of times higher in frequency than the fundamental square
wave.

If you poke said square wave with all it's noise into an L/C filter
it'll round it off into more of an approximation of a sin wave. You
only have to get rid of enough of the spikes/harmonics to keep from
confusing what ever you plan on running off the thing.
>
>Anybody wanna do an FFT of various duty-cycle waveforms, and give us real
>THD information, and how that relates to power factor, and etc, and etc,
>and etc?

You want power factor too?
Lordy, when I think of the caps we used to switch in on the power
mains at work depending on load. I doubt current and voltage were
ever in phase. Well, maybe with the exception of the time we fired
back up after doing PM on some switch gear and some one had forgotten
to remove the jumpers. Boy, but that was noisy! It actually bent the
cabinet doors into shallow U-shapes and those things were made of 1/8"
thick steel and about 7 or 8 feet tall.

>
>The one inverter I've ever had my hands on the guts of made a waveform
>like this:
>
> ---- ---- ----
> | | | | | |
> - - - - - -
> | | | | | etc.
>- ---- ----
>
>And the regulator was just based on an ordinary rectifier - they didn't
>care about RMS, or it was scaled to get "close enough".
>
They were just after "close enough". That's why the 400 watt PS in
one computer here weighs about a pound. The 500 watt in two others are
about 4# and the 630 is still heavier. BUT the 200 watt PS for my ham
rig weighs over 30#. I have a 600 watt (12 VDC @ 50 A) PS under the
desk that must weigh about 60 or 70#, None of the computer Power
supplies cost much over $50. I think the 400 was about $35. The big
one for the ham rig was several hundred dollars.

I have seen inverters that did a pretty good job on the output wave
form, but they were expensive and not nearly as efficient as the cheap
ones as a good portion of their work went into heat.

>But I do wonder, what does the harmonic content really do when you vary
>the duty cycle?

I would *guess* they would get pretty drastic at some portions
depending on just how hard the thing is working. There's not much
power in them so I'd expect to see them round off under load, but does
the inverter use dynamic filtering or hard filtering? Which is a good
way of saying I don't really know. <:-))

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
>
>Some years ago, in the USAF, I saw some pulses on a spectrum analyzer,
>and they had some really pretty envelopes. :-)
>
>Thanks,
>Rich

Roger

December 22nd 05, 02:52 AM

On Wed, 21 Dec 2005 14:29:00 GMT, Matt Whiting >
wrote:

>George Ghio wrote:
>
>> Tell us why anyone would modify a sine wave.
>
>To vary the power delivered to a load. Chopping off part of a sine wave
>cycle is a standard means of power control.
>

That makes three phase SCR (Silicon controlled rectifiers and not
saturable core reactors) interesting as chopping off part of the wave
form develops spikes and harmonics that tend to make the control of
one phase interact with the others.

I've built a lot of them for single phase control, but I never once
was able to build one for three phase that didn't interact. Turn one
up and maybe another would go up, Turn the second down and the other
two might go up or down. Twas interesting<:-)) which is probably why
Saturable core reactors are so popular in industry. Now there is a
controller that is a tad on the weighty side.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

>
>Matt

Roger

December 22nd 05, 02:54 AM

On 20 Dec 2005 22:50:51 -0800, "philkryder" >
wrote:

>"....We have a touch lamp that will not change
>state on MSW, but will on generator"
>
>Do you know if these new smaller Inverter style generators are a close
>enough approximation for things like the laser printer?
>
>Just how good are the "sine" like waves on them?
>
>I thought someone was going to put a 'scope on one...

The quality of the wave form is directly proportional to the money you
put into it.

I've used a small generator to power just about everything in here.
I've since upped that to 9,500 watts continuous which seems to work
well. It does tend to mess with the clocks if we're on generator
power for more than a few hours.

I've never had any problems with the computers of printers though.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Roger

December 22nd 05, 02:55 AM

On Wed, 21 Dec 2005 23:16:55 GMT, Rich Grise >
wrote:

>On Wed, 21 Dec 2005 14:06:05 -0500, Steve Spence wrote:
>
>> philkryder wrote:
>>> "....We have a touch lamp that will not change
>>> state on MSW, but will on generator"
>>>
>>> Do you know if these new smaller Inverter style generators are a close
>>> enough approximation for things like the laser printer?
>>>
>>> Just how good are the "sine" like waves on them?
>>>
>>> I thought someone was going to put a 'scope on one...
>>>
>>
>> I don't have one (inverter/generator) to test. If it's a SW then yes, it
>> will work. The HONDA EM50is claims to be a sine wave unit.
>
>It seems pretty obvious that a mechanical generator should put out a
>relatively pure sine wave - it's just this big rotating magnetic field and
>a couple of coils, after all. :-)
>
>As a matter of fact, it's a little hard for me to visualize how someone
>would make anything _other than_ a plain vanilla sine wave using just
>a rotating magnet and a coil.

Purchase a cheap one. They must try. <:-))

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
>
>Thanks!
>Rich
>

SolarFlare

December 22nd 05, 02:59 AM

When a scope is put on the waveform the shape is a
"modified sine wave"

This is not a hard concept.

"Steve Spence" > wrote in
message ...
> That's my point. There are modified square wave
inverters (marketed as
> Modified Sine Wave), and there are "Sine Wave"
inverters, which are
> really MSW's with such fine steps that finicky
equipment can't tell the
> difference. There are a few folks on this group
trying to justify the
> "Modified Sine Wave" sales moniker but there is no
logic to it. Folks
> who should know better, but can't find it easy to
"agree" with george
> even for a moment. It even kills me to do it, but
hey, he has a point
> for once.
>
>
> --
> Steve Spence
> Dir., Green Trust, http://www.green-trust.org
> Contributing Editor, http://www.off-grid.net
> http://www.rebelwolf.com/essn.html

SolarFlare

December 22nd 05, 03:06 AM

I guess you have no experience with creating digital
waveforms with a D/A converter and computer algoryths
then.

"Keith Williams" > wrote in message
T...

> BS. Were it unfiltered aliasing would make the CD
sound terrible.
> The filter has to be in there for any sampled system.
They didn't
> "all of a sudden" figure out that they needed a
filter.
>
> --
> Keith

Matt Whiting

December 22nd 05, 03:10 AM

Roger wrote:
> On Wed, 21 Dec 2005 14:29:00 GMT, Matt Whiting >
> wrote:
>
>
>>George Ghio wrote:
>>
>>
>>>Tell us why anyone would modify a sine wave.
>>
>>To vary the power delivered to a load. Chopping off part of a sine wave
>>cycle is a standard means of power control.
>>
>
>
> That makes three phase SCR (Silicon controlled rectifiers and not
> saturable core reactors) interesting as chopping off part of the wave
> form develops spikes and harmonics that tend to make the control of
> one phase interact with the others.
>
> I've built a lot of them for single phase control, but I never once
> was able to build one for three phase that didn't interact. Turn one
> up and maybe another would go up, Turn the second down and the other
> two might go up or down. Twas interesting<:-)) which is probably why
> Saturable core reactors are so popular in industry. Now there is a
> controller that is a tad on the weighty side.

The application I'm familiar with (well I was 10 years ago) was
electrically fired glass melting units. The resistive load didn't much
care about cross phase interference. :-)

Matt

George Ghio

December 22nd 05, 09:49 AM

No, it's not, it's a modified square wave

SolarFlare wrote:
> When a scope is put on the waveform the shape is a
> "modified sine wave"
>
> This is not a hard concept.
>
>
> "Steve Spence" > wrote in
> message ...
>
>>That's my point. There are modified square wave
>
> inverters (marketed as
>
>>Modified Sine Wave), and there are "Sine Wave"
>
> inverters, which are
>
>>really MSW's with such fine steps that finicky
>
> equipment can't tell the
>
>>difference. There are a few folks on this group
>
> trying to justify the
>
>>"Modified Sine Wave" sales moniker but there is no
>
> logic to it. Folks
>
>>who should know better, but can't find it easy to
>
> "agree" with george
>
>>even for a moment. It even kills me to do it, but
>
> hey, he has a point
>
>>for once.
>>
>>
>>--
>>Steve Spence
>>Dir., Green Trust, http://www.green-trust.org
>>Contributing Editor, http://www.off-grid.net
>>http://www.rebelwolf.com/essn.html
>
>
>

Roger

December 22nd 05, 11:04 AM

On Wed, 21 Dec 2005 15:48:32 GMT, Rich Grise >
wrote:

>On Tue, 20 Dec 2005 23:00:43 -0800, philkryder wrote:
>
>> "....It depends how you count "steps"."
>>
>> Indeed.
>>
>> I suppose something like "the number of distinct voltage changes per
>> cycle" might be a good first approximation of something to call steps
>> and to count.
>>
>> In your example I would count something like "3" or maybe "2" or "4" -
>> I always have trouble with boundary conditions...
>
>Heh. Programmers run into this all of the time - it's called "the
>fencepost effect". If you have a 100' fence, and there's a post
>every 10', how many posts do you need?

(100/10)+1 = 11
I used to farm.

>
>Or this one: Imagine a short staircase, say to a "sunken living
>room" or some such, of 3 steps:
>
>
> ------------
> |
> -----
> |
> -----
> |
> ---------------------------

There are only two steps. on the stairway. The others are landings

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Roger

December 22nd 05, 11:16 AM

On Thu, 22 Dec 2005 03:10:59 GMT, Matt Whiting >
wrote:

>Roger wrote:
>> On Wed, 21 Dec 2005 14:29:00 GMT, Matt Whiting >
>> wrote:
>>
>>
>>>George Ghio wrote:
>>>
>>>
>>>>Tell us why anyone would modify a sine wave.
>>>
>>>To vary the power delivered to a load. Chopping off part of a sine wave
>>>cycle is a standard means of power control.
>>>
>>
>>
>> That makes three phase SCR (Silicon controlled rectifiers and not
>> saturable core reactors) interesting as chopping off part of the wave
>> form develops spikes and harmonics that tend to make the control of
>> one phase interact with the others.
>>
>> I've built a lot of them for single phase control, but I never once
>> was able to build one for three phase that didn't interact. Turn one
>> up and maybe another would go up, Turn the second down and the other
>> two might go up or down. Twas interesting<:-)) which is probably why
>> Saturable core reactors are so popular in industry. Now there is a
>> controller that is a tad on the weighty side.
>
>The application I'm familiar with (well I was 10 years ago) was
>electrically fired glass melting units. The resistive load didn't much
>care about cross phase interference. :-)

The ones I'm referring to were large ovens with, I'd presume,
resistive elements as well. I finally gave up and purchased a
comercial unit.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
>
>Matt

Steve Spence

December 22nd 05, 03:22 PM

SolarFlare wrote:
> When a scope is put on the waveform the shape is a
> "modified sine wave"
>
> This is not a hard concept.
>
>

Actually it's not a modified sine wave, it's still a square wave with
many fine steps.
Again, it's a marketing term, not a technical one. You don't "modify"
the sine wave, you modify the square wave to approximate a sine wave.

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

Rich Grise

December 22nd 05, 03:40 PM

On Thu, 22 Dec 2005 10:22:48 -0500, Steve Spence wrote:

> SolarFlare wrote:
>> When a scope is put on the waveform the shape is a
>> "modified sine wave"
>>
>> This is not a hard concept.
>>
>>
>
>
> Actually it's not a modified sine wave, it's still a square wave with
> many fine steps.
> Again, it's a marketing term, not a technical one. You don't "modify"
> the sine wave, you modify the square wave to approximate a sine wave.

I like that one, but "approximated sine wave" just doesn't have the
same marketing ring to it. :-)

Cheers!
Rich

[email protected]

December 22nd 05, 04:58 PM

Why don't you ask this in the wind/solar electric NG you dumbass MoFo.

December 22nd 05, 06:02 PM

In article >,
Rich Grise > wrote:

> will work. The HONDA EM50is claims to be a sine wave unit.
>
> It seems pretty obvious that a mechanical generator should put out a
> relatively pure sine wave - it's just this big rotating magnetic field and
> a couple of coils, after all. :-)
>
> As a matter of fact, it's a little hard for me to visualize how someone
> would make anything _other than_ a plain vanilla sine wave using just
> a rotating magnet and a coil.
>
> Thanks!
> Rich

Except that if you actually had any understanding of the product you
were expounding upon, you would know that the generator portion of this
product, produces DC Current, that is then supplied to an internal
inverter, which then converts the DC current into AC current. The only
question being debated about the product is, if produces a true Sinewave
output, or a modified Squarewave output, during the conversion process.

Apparently you seem to lack visulization capabilities altogether.....

Me

daestrom

December 22nd 05, 08:36 PM

"Roger" > wrote in message
...
> On Wed, 21 Dec 2005 14:29:00 GMT, Matt Whiting >
> wrote:
>
>>George Ghio wrote:
>>
>>> Tell us why anyone would modify a sine wave.
>>
>>To vary the power delivered to a load. Chopping off part of a sine wave
>>cycle is a standard means of power control.
>>
>
> That makes three phase SCR (Silicon controlled rectifiers and not
> saturable core reactors) interesting as chopping off part of the wave
> form develops spikes and harmonics that tend to make the control of
> one phase interact with the others.
>
> I've built a lot of them for single phase control, but I never once
> was able to build one for three phase that didn't interact. Turn one
> up and maybe another would go up, Turn the second down and the other
> two might go up or down. Twas interesting<:-)) which is probably why
> Saturable core reactors are so popular in industry. Now there is a
> controller that is a tad on the weighty side.
>

Also, some old systems used self-saturating reactors (magnetic amplifiers,
'magamps') for instrumentation. Things could take some severe environments,
but calibration tended to drift a lot. Required fairly frequent 'trip &
cals' to keep them in spec.

daestrom

daestrom

December 22nd 05, 08:43 PM

"Keith Williams" > wrote in message
T...
> In article >,
> says...
<snip>
>> Except for one thing...when they played the CD back
>> unfiltered, people would find their tweeters melting
>> for some weird reason....44.1kHz! at huge powers!
>
> BS. Were it unfiltered aliasing would make the CD sound terrible.
> The filter has to be in there for any sampled system. They didn't
> "all of a sudden" figure out that they needed a filter.
>

Aliasing happens on the analog to digital conversion, not the digital to
analog conversion. That's why low-pass filters are put 'in front' of analog
to digital converters.

When going from digital to analog, all you *really* need is a sample/hold
circuit to maintain output until the next digital sample comes through for
conversion. But the step change from one sample to the next, if done with a
very fast slew rate can introduce some harmonics (rapid step changes are
always rich in high harmonics). But this is *not* aliasing ala Nyquist.
These can be 'smoothed' with a variety of filter circuits.

daestrom

Joel Kolstad

December 22nd 05, 11:05 PM

"daestrom" > wrote in message
...
> Aliasing happens on the analog to digital conversion, not the digital to
> analog conversion. That's why low-pass filters are put 'in front' of analog
> to digital converters.

You might not call it 'aliasing' -- it's arguably more appropriate to call it
'imaging' -- but a DAC that only outputs unit impulses scaled by the desired
output level creates infinitely many replicas of a band-limited sampled input
signal. Adding a first order (sample-and-) hold thereby gets you infinitely
many replicas scaled by a sinc function and -- as you mention -- typically
needs to be corrected or 'smoothed.' It isn't uncommon to purposely make use
of one the replicas, though, just as it isn't uncommon to sub-sample a
band-limited signal at well below its center frequency.

> But this is *not* aliasing ala Nyquist.

It's all just linear system convolution with sample functions, hold functions,
etc. 'Nyquist aliasing' is one of those kinda vauge terms where it's usually
clear from the context what's meant, but it doesn't have any particularly
formal meaning. (I can't tell you how many times I've seen people stating
something like, 'The Nyquist theorem requires sampling at at least twice the
highest frequency present in the signal," when of course it says no such
thing.)

---Joel Kolstad

Jim Carter

December 23rd 05, 12:26 AM

Finally, an excellent example of the purpose of a kill file...

> -----Original Message-----
> From: ]
> Posted At: Thursday, December 22, 2005 10:59 AM
> Posted To: rec.aviation.owning
> Conversation: Wind/Solar Electrics ???
> Subject: Re: Wind/Solar Electrics ???
>
> Why don't you ask this in the wind/solar electric NG you dumbass MoFo.

SolarFlare

December 23rd 05, 02:56 AM

Well, it ain't a perfect sinewave..it's a modified one.

"Rich Grise" > wrote in message
...
> On Thu, 22 Dec 2005 10:22:48 -0500, Steve Spence
wrote:
>
> > SolarFlare wrote:
> >> When a scope is put on the waveform the shape is a
> >> "modified sine wave"
> >>
> >> This is not a hard concept.
> >>
> >>
> >
> >
> > Actually it's not a modified sine wave, it's still
a square wave with
> > many fine steps.
> > Again, it's a marketing term, not a technical one.
You don't "modify"
> > the sine wave, you modify the square wave to
approximate a sine wave.
>
> I like that one, but "approximated sine wave" just
doesn't have the
> same marketing ring to it. :-)
>
> Cheers!
> Rich
>
>

SolarFlare

December 23rd 05, 02:59 AM

We still use saturable reactor based battery chargers
with a solid state feedback system for voltage and
current regulation. Still the latest and greatest, most
reliable technology we have in chargers. Not completely
mag amps but same idea.

Our mag amps use all went out years ago. I don't
remember ever having to recal them.

Wow! takes me back a ways...LOL

"daestrom" > wrote in
message
...
>
> "Roger" > wrote
in message
> ...
> > On Wed, 21 Dec 2005 14:29:00 GMT, Matt Whiting
>
> > wrote:
> >
> >>George Ghio wrote:
> >>
> >>> Tell us why anyone would modify a sine wave.
> >>
> >>To vary the power delivered to a load. Chopping
off part of a sine wave
> >>cycle is a standard means of power control.
> >>
> >
> > That makes three phase SCR (Silicon controlled
rectifiers and not
> > saturable core reactors) interesting as chopping
off part of the wave
> > form develops spikes and harmonics that tend to
make the control of
> > one phase interact with the others.
> >
> > I've built a lot of them for single phase control,
but I never once
> > was able to build one for three phase that didn't
interact. Turn one
> > up and maybe another would go up, Turn the second
down and the other
> > two might go up or down. Twas interesting<:-))
which is probably why
> > Saturable core reactors are so popular in industry.
Now there is a
> > controller that is a tad on the weighty side.
> >
>
> Also, some old systems used self-saturating reactors
(magnetic amplifiers,
> 'magamps') for instrumentation. Things could take
some severe environments,
> but calibration tended to drift a lot. Required
fairly frequent 'trip &
> cals' to keep them in spec.
>
> daestrom
>
>

SolarFlare

December 23rd 05, 03:01 AM

Three risers though.

"Roger" > wrote in
message
...
> >Or this one: Imagine a short staircase, say to a
"sunken living
> >room" or some such, of 3 steps:
> >
> >
> > ------------
> > |
> > -----
> > |
> > -----
> > |
>
---------------------------
>
> There are only two steps. on the stairway. The
others are landings
>
> Roger Halstead (K8RI & ARRL life member)
> (N833R, S# CD-2 Worlds oldest Debonair)
> www.rogerhalstead.com

philkryder

December 23rd 05, 03:49 AM

"MSW is a shysters sales pitch which misrepresents the product. "

Are there deterministic tests that tell when a device has a "good
enough" sine wave?
Or is there some sort of accepted "spec"?

I saw in another post where one of the EU2000 hondas had a beautiful
"looking" wave form, but failed to run a furnace.

What can we use to "know for sure" that the wave form of a device is
adequate BEFORE buying it?

Thanks
Phil

Rich Grise

December 23rd 05, 03:54 AM

On Thu, 22 Dec 2005 22:01:02 -0500, SolarFlare top-posted:

> Three risers though.

Yabbut, that misses the point of the gag. It's easy to point at the three
risers:

.. ------------
.. | <-- 1
, -----
.. | <--2
.. -----
.. | <-- 3
.. -------------

And, obviously, the middle one is #2.

But, while stepping up or down the stairs, the way most people count steps,
if you're going down, (to the right) you'd go:

.. ------------
.. | 1
, -----
.. | 2
.. -----
.. | 3
.. -------------

And count 3 steps. But if you're going up, which is right-to-left in
this exsample, you'd go:

3
.. ------------
.. | 2
, -----
.. | 1
.. -----
.. |
.. -------------

because where you started from is zero in either case, but step 2 is
different if you're going up or down.

Hope This Hemps!^H^H^H^Hlps! %-}
Rich

>
> "Roger" > wrote in
> message
> ...
>> >Or this one: Imagine a short staircase, say to a
> "sunken living
>> >room" or some such, of 3 steps:
>> >
>> >
>> > ------------
>> > |
>> > -----
>> > |
>> > -----
>> > |
>>
> ---------------------------
>>
>> There are only two steps. on the stairway. The
> others are landings
>>
>> Roger Halstead (K8RI & ARRL life member)
>> (N833R, S# CD-2 Worlds oldest Debonair)
>> www.rogerhalstead.com

[email protected]

December 23rd 05, 10:02 AM

Joel Kolstad > wrote:

>(I can't tell you how many times I've seen people stating something like,
>'The Nyquist theorem requires sampling at at least twice the highest
>frequency present in the signal," when of course it says no such thing.)

What do you think it means?

Nick

[email protected]

December 23rd 05, 10:07 AM

philkryder > wrote:

>Are there deterministic tests that tell when a device has a "good
>enough" sine wave? Or is there some sort of accepted "spec"?

I've seen a 5% total harmonic distortion spec. How many steps is that?

>What can we use to "know for sure" that the wave form of a device is
>adequate BEFORE buying it?

Try it out? I got a local dealer to start up an EU2000 and run it with
and without a muffler.

Nick

wmbjk

December 23rd 05, 03:04 PM

>On 22 Dec 2005 19:49:37 -0800, "philkryder" >
>wrote:

>>What can we use to "know for sure" that the wave form of a device is
>>adequate BEFORE buying it?

I've purchased a couple of ~$1500 machines from a local welding
supplier on condition that if there were any problems running them off
my SW inverters then the machines could be returned in as-new
condition the following day and I'd buy a different model instead.
That flexibility, and being able to see the machines in person, made
the extra cost of buying locally worthwhile.

Wayne

Joel Kolstad

December 23rd 05, 05:36 PM

> wrote in message
...
> Joel Kolstad > wrote:
>>(I can't tell you how many times I've seen people stating something like,
>>'The Nyquist theorem requires sampling at at least twice the highest
>>frequency present in the signal," when of course it says no such thing.)
>
> What do you think it means?

It means that perfect reconstruction of a signal requires sampling at at least
twice the _bandwidth_ of the signal present to insure that no aliasing occurs.

Two important points here:

1) It's the bandwidth of the signal that matters, not the highest frequency
present (this is kind of the analog version of the digitial guys' "it's the
edge rate that matters, not the clock speed"). This fact is frequently used
to great advantage in radio receivers (and plenty of other designs, I'm sure).
2) The assumption that aliasing is inherently detrimental is not always true.
I've seen designs where well-defined bandpass filters were stuck in front of
an ADC and the aliasing was used _to advantage_ to let the ADC sample at much
closer to 2x then one could have obtained with more traditional filter design.
(Although I'd admit that this seems to have been more common when ADCs were
slower and you had to use all the tricks you could to get performance out of
them.)

---Joel

December 23rd 05, 06:40 PM

In article . com>,
"philkryder" > wrote:

> "MSW is a shysters sales pitch which misrepresents the product. "
>
> Are there deterministic tests that tell when a device has a "good
> enough" sine wave?
> Or is there some sort of accepted "spec"?
>
> I saw in another post where one of the EU2000 hondas had a beautiful
> "looking" wave form, but failed to run a furnace.
>
> What can we use to "know for sure" that the wave form of a device is
> adequate BEFORE buying it?
>
> Thanks
> Phil
>

You can use a college education in Electrical Engineering, and $40K
worth of test equipment, to "KNOW FOR SURE"...... or you can fool
around and see what works........ or you can ask one who already
did the previous, and figured it out, and then actually believe what
they tell you........ other than that your on your own......

Me

daestrom

December 23rd 05, 06:46 PM

> wrote in message
...
> Joel Kolstad > wrote:
>
>>(I can't tell you how many times I've seen people stating something like,
>>'The Nyquist theorem requires sampling at at least twice the highest
>>frequency present in the signal," when of course it says no such thing.)
>
> What do you think it means?
>

Nyquist figured out that higher frequency components of the input signal
will 'alias' and you will lose the ability to tell them from lower frequency
components. In order to avoid 'losing information' and not being able to
tell whether a particular sample stream was from a low or high frequency
component, Nyquist's theorem states you must sample at least twice as fast
as the highest component present.
http://www.cs.cf.ac.uk/Dave/Multimedia/node149.html
http://www.efunda.com/designstandards/sensors/methods/dsp_nyquist.cfm

A lot of folks mistake it to think you need to sample at least twice as fast
as the 'signal of interest' also, and try to ignore high frequency
components of the input because they're 'not interested in that noise'. But
what Nyquist proved was that any frequency in the sampled signal that is
more than 1/2 the sample frequency will 'alias' and 'wrap around' and be
*indistinguisable* from a frequency component that is less than 1/2 the
sample frequency.

For example, if sampling at 1000 hz, and the sampled signal is a 900 hz
'pure sine wave', the sampled data would look *exactly* the same as if you
had sampled a 100 hz 'pure sine wave'. They would be 'indistinguisable'.
So if/when you try to convert the sampled data back to analog, how do you
know whether it should reconstruct a 100 hz wave, or 900 hz? You don't, so
you have a conundrum.

So, to avoid losing this 'information' of being able to tell if you had a
100 hz or 900 hz input, the standard thing to do is filter the input so that
there is *no* 900 hz input. Then, the resulting sample data must have come
from the 100 hz component. And if/when you want to reconstruct it, you
*know* it should form a 100 hz signal because no 900 hz signal could
possibly been present (you eliminated it before sampling).

And as Joel mentioned earlier, since most low-pass filters do not have
perfect 'cutoff' (IIRC, simple first-orders 'roll off' at something like 3
db/decade), it is more common to eliminate any frequency component that is
more than about 40% of the sampling frequency.

daestrom

Spehro Pefhany

December 23rd 05, 07:09 PM

On Fri, 23 Dec 2005 18:46:49 GMT, the renowned "daestrom"
> wrote:

>
> wrote in message
...
>> Joel Kolstad > wrote:
>>
>>>(I can't tell you how many times I've seen people stating something like,
>>>'The Nyquist theorem requires sampling at at least twice the highest
>>>frequency present in the signal," when of course it says no such thing.)
>>
>> What do you think it means?
>>
>
>Nyquist figured out that higher frequency components of the input signal
>will 'alias' and you will lose the ability to tell them from lower frequency
>components. In order to avoid 'losing information' and not being able to
>tell whether a particular sample stream was from a low or high frequency
>component, Nyquist's theorem states you must sample at least twice as fast
>as the highest component present.
<snip>

More than twice the bandwidth.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

SolarFlare

December 23rd 05, 07:25 PM

With risers it is the same confusion.

"Rich Grise" > wrote in
message
t...
> On Thu, 22 Dec 2005 22:01:02 -0500, SolarFlare
top-posted:
>
> > Three risers though.
>
> Yabbut, that misses the point of the gag. It's easy
to point at the three
> risers:
>
> . ------------
> . | <-- 1
> , -----
> . | <--2
> . -----
> . | <-- 3
> . -------------
>
> And, obviously, the middle one is #2.
>
> But, while stepping up or down the stairs, the way
most people count steps,
> if you're going down, (to the right) you'd go:
>
>
> . ------------
> . | 1
> , -----
> . | 2
> . -----
> . | 3
> . -------------
>
> And count 3 steps. But if you're going up, which is
right-to-left in
> this exsample, you'd go:
>
>
> 3
> . ------------
> . | 2
> , -----
> . | 1
> . -----
> . |
> . -------------
>
> because where you started from is zero in either
case, but step 2 is
> different if you're going up or down.
>
> Hope This Hemps!^H^H^H^Hlps! %-}
> Rich
>
>
> >
> > "Roger" > wrote
in
> > message
> > ...
> >> >Or this one: Imagine a short staircase, say to a
> > "sunken living
> >> >room" or some such, of 3 steps:
> >> >
> >> >
> >> > ------------
> >> > |
> >> > -----
> >> > |
> >> > -----
> >> > |
> >>
> > ---------------------------
> >>
> >> There are only two steps. on the stairway. The
> > others are landings
> >>
> >> Roger Halstead (K8RI & ARRL life member)
> >> (N833R, S# CD-2 Worlds oldest Debonair)
> >> www.rogerhalstead.com
>

[email protected]

December 23rd 05, 07:43 PM

Joel Kolstad > wrote:

>1) It's the bandwidth of the signal that matters, not the highest frequency
>present...

One might say "the highest frequency present" is the highest frequency
non-zero component of the power spectrum.

Nick

Joel Kolstad

December 23rd 05, 08:07 PM

> wrote in message
...
> Joel Kolstad > wrote:
>>1) It's the bandwidth of the signal that matters, not the highest frequency
>>present...
> One might say "the highest frequency present" is the highest frequency
> non-zero component of the power spectrum.

Sure, but the point is that you can sample a signal that's has all (of a good
approximation thereof, e.g., 99%) of its energy between 144-148MHz (this is
the 2m amateur radio band) at 10MSps and recover everything. I.e., the
bandwidth of the signal is only 4MHz, so you only have to sample at something
>8MSps.

Ray Andraka

December 23rd 05, 08:36 PM

Joel Kolstad wrote:

Hey Joel, what are you doing over here. Are you a pilot too?

I've used this for subsampling, although you have to be very careful of
clock jitter when you sub-sample. a couple picoseconds of jitter on the
sampling of a 100 MHz signal is going to add substantial noise to the
signal.

(subsampling, for those here who haven't a clue what we are talking
about...this is an airplane owner's forum after all...is taking
advantage of the nyquist theorum to sample at less than the frequencyt
of the signal when the bandwidth of the signal is narrow. For example,
if you have a signal centered at 100 Mhz that only has a 10 MHz
bandwidth, you can sample it at something less than 100 MHz and still
recover all of the information. The more generally held belief is that
you would need to sample it at greater than 200 MHz in order to not lose
information).

Joel Kolstad

December 23rd 05, 08:56 PM

"Ray Andraka" > wrote in message
news:deZqf.31975$Mi5.3388@dukeread07...
> Hey Joel, what are you doing over here. Are you a pilot too?

Hi Ray!

Hmmm... no, I'm not a pilot, I just got sucked in by the cross-posting
(starting from sci.electronics.design) and the topic has drifted considerably
since it started.

> I've used this for subsampling, although you have to be very careful of
> clock jitter when you sub-sample. a couple picoseconds of jitter on the
> sampling of a 100 MHz signal is going to add substantial noise to the
> signal.

Yes it is... I suspect that's why that projects such as GNURadio (which
sub-samples using something like 80 or 100MSps ADCs) tend not to be as
sensitive as more traditional analog receivers. (Someone made the comment
that the FM decoder in GNURadio doesn't really even work as well as a $5
transistor radio, which is true enough albeit perhaps missing the point of how
cool/fun it is to be able to write any modulator/demodulator you like if
you're not looking for the ultimate sensitivty.)

>(For example, if you have a signal centered at 100 Mhz that only has a 10
>MHz bandwidth, you can sample it at something less than 100 MHz and still
>recover all of the information. The more generally held belief is that you
>would need to sample it at greater than 200 MHz in order to not lose
>information).

I believe that folks who think you need to sample at 200MHz (the intuitively
reaosnable answer) are those who were never made to /had the opportunity to
open up an undergraduate signals & systems book. :-) Thinking about things
like modulation are so much cleaner in the frequency domain once one gets the
whole "multiplication in one domain is convolution in the other" bit down.

---Joel

George Ghio

December 23rd 05, 10:31 PM

Yes this is the problem. While there are people who will tell you
anything to make a sale, how do you know what you are really getting.

One test is the "Modified Square Wave" test.

When you hear these words you know you are dealing either with a shyster
or an ignorant person who should not be selling things he does not
understand.

It is hard, what with a flood of imports at bargain basement prices.

Still, as long as people are willing to believe that a $59 3000W
"modified sine wave" inverter from Walmart, Cost Co, etc, etc has the
same specs as a $900 3000W sine inverter is, at best, fooling themselves.

I buy inverters from known manufacturers who are willing to provide spec
sheets that out line the full parameters of the inverter. You know
things like:

Efficiency curves
Max continuous output
1/2 hour rating
Surge
Standby
Max DC in

Well everything really.

I did build a kit inverter, once, years ago. It had a max rating of
150W, Which it met.

It had a half hour rating of 0W

And a surge of about 300W

Still it did the job it was built to do for many years.

Put your supplier on the spot. Tell them your load and buy on the
condition that what they are selling you will do what they claim or you
get a full refund, no questions asked.

philkryder wrote:
> "MSW is a shysters sales pitch which misrepresents the product. "
>
> Are there deterministic tests that tell when a device has a "good
> enough" sine wave?
> Or is there some sort of accepted "spec"?
>
> I saw in another post where one of the EU2000 hondas had a beautiful
> "looking" wave form, but failed to run a furnace.
>
> What can we use to "know for sure" that the wave form of a device is
> adequate BEFORE buying it?
>
> Thanks
> Phil
>

George Ghio

December 23rd 05, 10:33 PM

A fine example of the correct approach.

wmbjk wrote:
>>On 22 Dec 2005 19:49:37 -0800, "philkryder" >
>>wrote:
>
>
>>>What can we use to "know for sure" that the wave form of a device is
>>>adequate BEFORE buying it?
>
>
> I've purchased a couple of ~$1500 machines from a local welding
> supplier on condition that if there were any problems running them off
> my SW inverters then the machines could be returned in as-new
> condition the following day and I'd buy a different model instead.
> That flexibility, and being able to see the machines in person, made
> the extra cost of buying locally worthwhile.
>
> Wayne

wmbjk

December 24th 05, 12:52 AM

On Sat, 24 Dec 2005 09:31:50 +1100, George Ghio >
wrote:

>One test is the "Modified Square Wave" test.
>
>When you hear these words you know you are dealing either with a shyster
>or an ignorant person who should not be selling things he does not
>understand.

The only thing your test proves is that you're irrationally
judgmental.

>It is hard, what with a flood of imports at bargain basement prices.
>
>Still, as long as people are willing to believe that a $59 3000W
>"modified sine wave" inverter from Walmart, Cost Co, etc, etc has the
>same specs as a $900 3000W sine inverter is, at best, fooling themselves.

Why do you give buyers so little credit? And where does one buy a
3000W sine-wave inverter for $900?

Wayne

wmbjk

December 24th 05, 12:53 AM

On Sat, 24 Dec 2005 09:33:02 +1100, George Ghio >
wrote:

>>>On 22 Dec 2005 19:49:37 -0800, "philkryder" >
>>>wrote:

>>>>What can we use to "know for sure" that the wave form of a device is
>>>>adequate BEFORE buying it?

>wmbjk wrote:

>> I've purchased a couple of ~$1500 machines from a local welding
>> supplier on condition that if there were any problems running them off
>> my SW inverters then the machines could be returned in as-new
>> condition the following day and I'd buy a different model instead.
>> That flexibility, and being able to see the machines in person, made
>> the extra cost of buying locally worthwhile.
>>
>> Wayne

>A fine example of the correct approach.

Oh crap. Since your agreement has to be counted as a negative, now
anyone reading will have to wait for someone credible to concur.

Wayne

[email protected]

December 24th 05, 07:57 AM

George Ghio wrote:

> I did build a kit inverter, once, years ago. It had a max rating of
> 150W, Which it met.
>
> It had a half hour rating of 0W
>
> And a surge of about 300W

I'm still scratching my head over that one.

NT

[email protected]

December 24th 05, 08:01 AM

Joel Kolstad wrote:
> > wrote in message
> ...
> > Joel Kolstad > wrote:
> >>1) It's the bandwidth of the signal that matters, not the highest frequency
> >>present...
> > One might say "the highest frequency present" is the highest frequency
> > non-zero component of the power spectrum.
>
> Sure, but the point is that you can sample a signal that's has all (of a good
> approximation thereof, e.g., 99%) of its energy between 144-148MHz (this is
> the 2m amateur radio band) at 10MSps and recover everything. I.e., the
> bandwidth of the signal is only 4MHz, so you only have to sample at something
> >8MSps.

IIUC that woudl demodulate the signal too?

NT

Steve Spence

December 24th 05, 02:42 PM

wrote:
> George Ghio wrote:
>
>
>>I did build a kit inverter, once, years ago. It had a max rating of
>>150W, Which it met.
>>
>>It had a half hour rating of 0W
>>
>>And a surge of about 300W
>
>
> I'm still scratching my head over that one.
>
>
> NT
>

That's standard with george's posts. Don't get a splinter.

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

daestrom

December 24th 05, 05:10 PM

"Joel Kolstad" > wrote in message
...
> > wrote in message
> ...
>> Joel Kolstad > wrote:
>>>1) It's the bandwidth of the signal that matters, not the highest
>>>frequency
>>>present...
>> One might say "the highest frequency present" is the highest frequency
>> non-zero component of the power spectrum.
>
> Sure, but the point is that you can sample a signal that's has all (of a
> good approximation thereof, e.g., 99%) of its energy between 144-148MHz
> (this is the 2m amateur radio band) at 10MSps and recover everything.
> I.e., the bandwidth of the signal is only 4MHz, so you only have to sample
> at something
> >8MSps.
>

Only if you demodulate the signal first.

daestrom

daestrom

December 24th 05, 05:10 PM

"Spehro Pefhany" > wrote in message
...
> On Fri, 23 Dec 2005 18:46:49 GMT, the renowned "daestrom"
> > wrote:
>
>>
> wrote in message
...
>>> Joel Kolstad > wrote:
>>>
>>>>(I can't tell you how many times I've seen people stating something
>>>>like,
>>>>'The Nyquist theorem requires sampling at at least twice the highest
>>>>frequency present in the signal," when of course it says no such thing.)
>>>
>>> What do you think it means?
>>>
>>
>>Nyquist figured out that higher frequency components of the input signal
>>will 'alias' and you will lose the ability to tell them from lower
>>frequency
>>components. In order to avoid 'losing information' and not being able to
>>tell whether a particular sample stream was from a low or high frequency
>>component, Nyquist's theorem states you must sample at least twice as fast
>>as the highest component present.
> <snip>
>
> More than twice the bandwidth.
>
>

So, if I have a signal with a 1000 hz carrier, with a bandwidth of 50 hz,
you think I can sample it at just 150 hz and get accurate reproduction?
That's just wrong.

It is the maximum frequency component in the signal that is important. The
bandwidth is not related unless the lower edge of the band is at 0 hz
(whereupon the upper side of the band is equal to the max frequency).

daestrom

daestrom

December 24th 05, 05:15 PM

"George Ghio" > wrote in message
...
> Yes this is the problem. While there are people who will tell you anything
> to make a sale, how do you know what you are really getting.
>
> One test is the "Modified Square Wave" test.
>
> When you hear these words you know you are dealing either with a shyster
> or an ignorant person who should not be selling things he does not
> understand.
>

Judging from your previous posts, I think you mean when you hear "Modified
*sine* wave", then you know you are dealing with shyster or an ignorant
person...."

A salesperson that says their unit puts out a modified *square* wave would
be a sign[sic] of a knowledgable salesperson.

daestrom

SolarFlare

December 24th 05, 05:17 PM

Off your medication again Steve?

"Steve Spence" > wrote in
message ...
> wrote:
> > George Ghio wrote:
> >
> >
> >>I did build a kit inverter, once, years ago. It had
a max rating of
> >>150W, Which it met.
> >>
> >>It had a half hour rating of 0W
> >>
> >>And a surge of about 300W
> >
> >
> > I'm still scratching my head over that one.
> >
> >
> > NT
> >
>
> That's standard with george's posts. Don't get a
splinter.
>
> --
> Steve Spence
> Dir., Green Trust, http://www.green-trust.org
> Contributing Editor, http://www.off-grid.net
> http://www.rebelwolf.com/essn.html

SolarFlare

December 24th 05, 05:18 PM

Simple hetrodyne system will do that. No demodulating
required.

"daestrom" > wrote in
message
...
>
> "Joel Kolstad" > wrote
in message
> ...

> > Sure, but the point is that you can sample a signal
that's has all (of a
> > good approximation thereof, e.g., 99%) of its
energy between 144-148MHz
> > (this is the 2m amateur radio band) at 10MSps and
recover everything.
> > I.e., the bandwidth of the signal is only 4MHz, so
you only have to sample
> > at something
> > >8MSps.
> >
>
> Only if you demodulate the signal first.
>
> daestrom
>
>

SolarFlare

December 24th 05, 05:22 PM

You can represent the bandwidth with double the
sampling rate as the bandwidth frequency but there is a
component missing from the sample information that has
to be known and is not part of the samples. Namely the
base frequency has to be added back into the formula.

"daestrom" > wrote in
message
...
>
> So, if I have a signal with a 1000 hz carrier, with a
bandwidth of 50 hz,
> you think I can sample it at just 150 hz and get
accurate reproduction?
> That's just wrong.
>
> It is the maximum frequency component in the signal
that is important. The
> bandwidth is not related unless the lower edge of the
band is at 0 hz
> (whereupon the upper side of the band is equal to the
max frequency).
>
> daestrom
>
>

December 24th 05, 06:28 PM

In article >,
"daestrom" > wrote:

> "Spehro Pefhany" > wrote in message
> ...
> > On Fri, 23 Dec 2005 18:46:49 GMT, the renowned "daestrom"
> > > wrote:
> >
> >>
> > wrote in message
> ...
> >>> Joel Kolstad > wrote:
> >>>
> >>>>(I can't tell you how many times I've seen people stating something
> >>>>like,
> >>>>'The Nyquist theorem requires sampling at at least twice the highest
> >>>>frequency present in the signal," when of course it says no such thing.)
> >>>
> >>> What do you think it means?
> >>>
> >>
> >>Nyquist figured out that higher frequency components of the input signal
> >>will 'alias' and you will lose the ability to tell them from lower
> >>frequency
> >>components. In order to avoid 'losing information' and not being able to
> >>tell whether a particular sample stream was from a low or high frequency
> >>component, Nyquist's theorem states you must sample at least twice as fast
> >>as the highest component present.
> > <snip>
> >
> > More than twice the bandwidth.
> >
> >
>
> So, if I have a signal with a 1000 hz carrier, with a bandwidth of 50 hz,
> you think I can sample it at just 150 hz and get accurate reproduction?
> That's just wrong.
>
> It is the maximum frequency component in the signal that is important. The
> bandwidth is not related unless the lower edge of the band is at 0 hz
> (whereupon the upper side of the band is equal to the max frequency).
>
> daestrom
>
>

You are getting your terms confused here guys. Nyquist requires that
you input both the Center Frequency, and Bandwidth when determining
the Sampling Rate. If the sampling is done at BaseBand then only the
Bandwidth is relevent. If the sampling is not done at baseband, then
the Center Frequency, and Bandwidth are required to determine samling
rate. Example, if the Bandwith of the signal is 3Kc and the sampling is
done at BaseBand then sample rate needed would 6Kc. If the sampling is
done at 100 Mhz with the same 3Kc bandwidth, then a 200.006 Mhz sampling
rate would be required.

It is much easyier to do DSP at baseBand, than at IF Frequencies, and if
you do DSP at IF Frequencies, the lower the IF Frequency, the easyier it
is to do, and the slower the DSP has to run.

Me

SolarFlare

December 24th 05, 06:49 PM

If only the baseband frequency is sampled at 6kHz then
information is missing to recreate the original 100kHz
and the sampling information is insufficient to
recreate the original signal.

This is analogous to saying the number 1234 can be
represented by
(1234-234) / 1000 = 1

If I supply the number 1.0 you can regenerate the
number 1234 from it? Not true, without the rest of the
sampling information. The sample is incomplete.

Bandwidth sampling only cannot recreate the original
signal.

"Me" > wrote in message
...
> In article
>,
> "daestrom" >
wrote:
>
> > "Spehro Pefhany"
> wrote in message
> > ...
> > > On Fri, 23 Dec 2005 18:46:49 GMT, the renowned
"daestrom"
> > > > wrote:
> > >
> > >>
> > > wrote in message
> > ...
> > >>> Joel Kolstad >
wrote:
> > >>>
> > >>>>(I can't tell you how many times I've seen
people stating something
> > >>>>like,
> > >>>>'The Nyquist theorem requires sampling at at
least twice the highest
> > >>>>frequency present in the signal," when of
course it says no such thing.)
> > >>>
> > >>> What do you think it means?
> > >>>
> > >>
> > >>Nyquist figured out that higher frequency
components of the input signal
> > >>will 'alias' and you will lose the ability to
tell them from lower
> > >>frequency
> > >>components. In order to avoid 'losing
information' and not being able to
> > >>tell whether a particular sample stream was from
a low or high frequency
> > >>component, Nyquist's theorem states you must
sample at least twice as fast
> > >>as the highest component present.
> > > <snip>
> > >
> > > More than twice the bandwidth.
> > >
> > >
> >
> > So, if I have a signal with a 1000 hz carrier, with
a bandwidth of 50 hz,
> > you think I can sample it at just 150 hz and get
accurate reproduction?
> > That's just wrong.
> >
> > It is the maximum frequency component in the signal
that is important. The
> > bandwidth is not related unless the lower edge of
the band is at 0 hz
> > (whereupon the upper side of the band is equal to
the max frequency).
> >
> > daestrom
> >
> >
>
> You are getting your terms confused here guys.
Nyquist requires that
> you input both the Center Frequency, and Bandwidth
when determining
> the Sampling Rate. If the sampling is done at
BaseBand then only the
> Bandwidth is relevent. If the sampling is not done
at baseband, then
> the Center Frequency, and Bandwidth are required to
determine samling
> rate. Example, if the Bandwith of the signal is 3Kc
and the sampling is
> done at BaseBand then sample rate needed would 6Kc.
If the sampling is
> done at 100 Mhz with the same 3Kc bandwidth, then a
200.006 Mhz sampling
> rate would be required.
>
> It is much easyier to do DSP at baseBand, than at IF
Frequencies, and if
> you do DSP at IF Frequencies, the lower the IF
Frequency, the easyier it
> is to do, and the slower the DSP has to run.
>
> Me

wmbjk

December 24th 05, 09:20 PM

On 23 Dec 2005 23:57:27 -0800, wrote:

>George Ghio wrote:
>
>> I did build a kit inverter, once, years ago. It had a max rating of
>> 150W, Which it met.
>>
>> It had a half hour rating of 0W
>>
>> And a surge of about 300W

>I'm still scratching my head over that one.
>
>
>NT

He previously wrote about using either a 150 Ohm rheostat (other times
referred to as 150A or 200A), or 300k nichrome wire to control a few
Amps of field current on a small 12V automotive alternator. According
to the "designer" (who often refers to himself as a "solar power
consultant"), 150 Ohms didn't allow sufficiently low output, hence the
need for the nichrome wire. And as we all know, the prime
consideration on a home-power generator is low output. <snorf> Similar
wisdom surely underpins his other projects. For instance, liberal
application of 300k wire might be useful when building a max 150, peak
300, zero Watt inverter, or most any zero Watt inverter for that
matter. Perhaps strung around the property in large coils like razor
wire at Slinky Manor. ;-)

Wayne

George Ghio

December 25th 05, 06:46 AM

Take the credit when you can as it does not happen that often.

wmbjk wrote:
> On Sat, 24 Dec 2005 09:33:02 +1100, George Ghio >
> wrote:
>
>
>>>>On 22 Dec 2005 19:49:37 -0800, "philkryder" >
>>>>wrote:
>
>
>>>>>What can we use to "know for sure" that the wave form of a device is
>>>>>adequate BEFORE buying it?
>
>
>>wmbjk wrote:
>
>
>>>I've purchased a couple of ~$1500 machines from a local welding
>>>supplier on condition that if there were any problems running them off
>>>my SW inverters then the machines could be returned in as-new
>>>condition the following day and I'd buy a different model instead.
>>>That flexibility, and being able to see the machines in person, made
>>>the extra cost of buying locally worthwhile.
>>>
>>>Wayne
>
>
>>A fine example of the correct approach.
>
>
> Oh crap. Since your agreement has to be counted as a negative, now
> anyone reading will have to wait for someone credible to concur.
>
> Wayne

George Ghio

December 25th 05, 06:48 AM

Which part don't you understand

wrote:
> George Ghio wrote:
>
>
>>I did build a kit inverter, once, years ago. It had a max rating of
>>150W, Which it met.
>>
>>It had a half hour rating of 0W
>>
>>And a surge of about 300W
>
>
> I'm still scratching my head over that one.
>
>
> NT
>

George Ghio

December 25th 05, 06:50 AM

I'll pay that. Thank you for the correction. Spent too many hours under
the car, I guess.

daestrom wrote:
> "George Ghio" > wrote in message
> ...
>
>>Yes this is the problem. While there are people who will tell you anything
>>to make a sale, how do you know what you are really getting.
>>
>>One test is the "Modified Square Wave" test.
>>
>>When you hear these words you know you are dealing either with a shyster
>>or an ignorant person who should not be selling things he does not
>>understand.
>>
>
>
> Judging from your previous posts, I think you mean when you hear "Modified
> *sine* wave", then you know you are dealing with shyster or an ignorant
> person...."
>
> A salesperson that says their unit puts out a modified *square* wave would
> be a sign[sic] of a knowledgable salesperson.
>
> daestrom
>
>

Roger

December 25th 05, 07:39 AM

On Thu, 22 Dec 2005 20:36:17 GMT, "daestrom"
> wrote:

>
>"Roger" > wrote in message
...
>> On Wed, 21 Dec 2005 14:29:00 GMT, Matt Whiting >
>> wrote:
>>
>>>George Ghio wrote:
>>>
>>>> Tell us why anyone would modify a sine wave.
>>>
>>>To vary the power delivered to a load. Chopping off part of a sine wave
>>>cycle is a standard means of power control.
>>>
>>
>> That makes three phase SCR (Silicon controlled rectifiers and not
>> saturable core reactors) interesting as chopping off part of the wave
>> form develops spikes and harmonics that tend to make the control of
>> one phase interact with the others.
>>
>> I've built a lot of them for single phase control, but I never once
>> was able to build one for three phase that didn't interact. Turn one
>> up and maybe another would go up, Turn the second down and the other
>> two might go up or down. Twas interesting<:-)) which is probably why
>> Saturable core reactors are so popular in industry. Now there is a
>> controller that is a tad on the weighty side.
>>
>
>Also, some old systems used self-saturating reactors (magnetic amplifiers,
>'magamps') for instrumentation. Things could take some severe environments,
>but calibration tended to drift a lot. Required fairly frequent 'trip &
>cals' to keep them in spec.

For the small and large stuff we used solid state SCRs while the
intermediate still used saturable core reactors. 10 years ago I think
they still had some mag amps, but the ones we had were pretty stable.

They use larger SCRs now, but I have the silicon wafer out of one that
is over 1 1/2" in diameter. They operated up to 480 and 1000 Amps
and ran near maximum for many hours. The SCRs themselves were about
the size of a hockey puck or slightly larger.

Now there was some power and I'd guess they use much larger systems
now.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
>
>daestrom
>

Hal Murray

December 25th 05, 11:29 AM

>So, if I have a signal with a 1000 hz carrier, with a bandwidth of 50 hz,
>you think I can sample it at just 150 hz and get accurate reproduction?
>That's just wrong.

No, that's the whole point of this discussion.

You have to understand aliasing. The signal you want aliases
down into the baseband. Your anti-aliaising filter has
to get rid of all the junk you don't want. In this case it
includes the baseband. Since there is no baseband signal
(or other out-of-band junk) you can reconstruct the original
signal.

It's a common trick with software radios.

You do need some extra information that doesn't go in through
the A/D channel. That's the design of the system, in particular
what the anti-aliasing filter lets through.

Maybe the reason that this is so confusing is that you also need
that info the the normal/baseband case. But since that's the normal
case we don't bother mentioning it.

--
The suespammers.org mail server is located in California. So are all my
other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's. I hate spam.

wmbjk

December 25th 05, 03:29 PM

On Sun, 25 Dec 2005 17:50:50 +1100, George Ghio >
wrote:

>> "George Ghio" > wrote in message
>> ...
>>
>>>Yes this is the problem. While there are people who will tell you anything
>>>to make a sale, how do you know what you are really getting.
>>>
>>>One test is the "Modified Square Wave" test.
>>>
>>>When you hear these words you know you are dealing either with a shyster
>>>or an ignorant person who should not be selling things he does not
>>>understand.

>daestrom wrote:>>
>> Judging from your previous posts, I think you mean when you hear "Modified
>> *sine* wave", then you know you are dealing with shyster or an ignorant
>> person...."
>>
>> A salesperson that says their unit puts out a modified *square* wave would
>> be a sign[sic] of a knowledgable salesperson.
>>
>> daestrom

>I'll pay that. Thank you for the correction. Spent too many hours under
>the car, I guess.

OHMYGOD! A blunder admitted! Who the hell are you and what have you
done with George Ghio?

Wayne

PS It's in everyone's best interest that you not be found out, so
don't forget to hide your pod.

SolarFlare

December 25th 05, 06:58 PM

Where is the baseband information stored if it isn't
encoded into the sampling?

"Hal Murray" > wrote in message
...
> >So, if I have a signal with a 1000 hz carrier, with
a bandwidth of 50 hz,
> >you think I can sample it at just 150 hz and get
accurate reproduction?
> >That's just wrong.
>
> No, that's the whole point of this discussion.
>
> You have to understand aliasing. The signal you want
aliases
> down into the baseband. Your anti-aliaising filter
has
> to get rid of all the junk you don't want. In this
case it
> includes the baseband. Since there is no baseband
signal
> (or other out-of-band junk) you can reconstruct the
original
> signal.
>
> It's a common trick with software radios.
>
> You do need some extra information that doesn't go in
through
> the A/D channel. That's the design of the system, in
particular
> what the anti-aliasing filter lets through.
>
> Maybe the reason that this is so confusing is that
you also need
> that info the the normal/baseband case. But since
that's the normal
> case we don't bother mentioning it.
>
> --
> The suespammers.org mail server is located in
California. So are all my
> other mailboxes. Please do not send unsolicited bulk
e-mail or unsolicited
> commercial e-mail to my suespammers.org address or
any of my other addresses.
> These are my opinions, not necessarily my employer's.
I hate spam.
>

Hal Murray

December 25th 05, 09:19 PM

>Where is the baseband information stored if it isn't
>encoded into the sampling?

I'm not sure what you are asking.

If you have a 1 MHz carrier with 1 KHz of bandwidth,
you might do something like sample at 10 KHz so
your anti-alias filter has some room to work with.
Then you feed the signal into a FFT and throw away
the buckets that the filter didn't get rid of.

You often pick the sampling frequency so the FFT buckets
(after aliasing) come out on convenient numbers.

If by "baseband" you mean the raw signal between 0 and X,
there isn't any information between 0 and X-tiny in a typical
narrow band modulated signal.

If you are doing the aliasing trick, the anti-aliasing filter
has to block the baseband junk (noise) or it will get into the
A/D and confuse things. It's the reverse of the "normal" anti-alias
filter that gets rid of the noise above the baseband so it doesn't
alias down and trash your signal.

--
The suespammers.org mail server is located in California. So are all my
other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's. I hate spam.

George Ghio

December 25th 05, 11:20 PM

George is alive and well and full of Christmas cheer.

Merry Christmas to all and may you all have a great solar new year.

Even you Wayne.

wmbjk wrote:
> On Sun, 25 Dec 2005 17:50:50 +1100, George Ghio >
> wrote:
>
>
>>>"George Ghio" > wrote in message
...
>>>
>>>
>>>>Yes this is the problem. While there are people who will tell you anything
>>>>to make a sale, how do you know what you are really getting.
>>>>
>>>>One test is the "Modified Square Wave" test.
>>>>
>>>>When you hear these words you know you are dealing either with a shyster
>>>>or an ignorant person who should not be selling things he does not
>>>>understand.
>
>
>>daestrom wrote:>>
>>
>>>Judging from your previous posts, I think you mean when you hear "Modified
>>>*sine* wave", then you know you are dealing with shyster or an ignorant
>>>person...."
>>>
>>>A salesperson that says their unit puts out a modified *square* wave would
>>>be a sign[sic] of a knowledgable salesperson.
>>>
>>>daestrom
>
>
>>I'll pay that. Thank you for the correction. Spent too many hours under
>>the car, I guess.
>
>
> OHMYGOD! A blunder admitted! Who the hell are you and what have you
> done with George Ghio?
>
> Wayne
>
> PS It's in everyone's best interest that you not be found out, so
> don't forget to hide your pod.

SolarFlare

December 26th 05, 03:13 AM

You too George.

Merry Christmas to Wayne and all his socks.

"George Ghio" > wrote in message
...
> George is alive and well and full of Christmas cheer.
>
> Merry Christmas to all and may you all have a great
solar new year.
>
> Even you Wayne.
>
> wmbjk wrote:
> > On Sun, 25 Dec 2005 17:50:50 +1100, George Ghio
>
> > wrote:
> >
> >
> >>>"George Ghio" > wrote in
message
> ...
> >>>
> >>>
> >>>>Yes this is the problem. While there are people
who will tell you anything
> >>>>to make a sale, how do you know what you are
really getting.
> >>>>
> >>>>One test is the "Modified Square Wave" test.
> >>>>
> >>>>When you hear these words you know you are
dealing either with a shyster
> >>>>or an ignorant person who should not be selling
things he does not
> >>>>understand.
> >
> >
> >>daestrom wrote:>>
> >>
> >>>Judging from your previous posts, I think you mean
when you hear "Modified
> >>>*sine* wave", then you know you are dealing with
shyster or an ignorant
> >>>person...."
> >>>
> >>>A salesperson that says their unit puts out a
modified *square* wave would
> >>>be a sign[sic] of a knowledgable salesperson.
> >>>
> >>>daestrom
> >
> >
> >>I'll pay that. Thank you for the correction. Spent
too many hours under
> >>the car, I guess.
> >
> >
> > OHMYGOD! A blunder admitted! Who the hell are you
and what have you
> > done with George Ghio?
> >
> > Wayne
> >
> > PS It's in everyone's best interest that you not
be found out, so
> > don't forget to hide your pod.

SolarFlare

December 26th 05, 05:14 AM

The point is the sampling rate has to be done at just
over double the frequency of the signal and not the
bandwidth.

"Hal Murray" > wrote in message
...
> >Where is the baseband information stored if it isn't
> >encoded into the sampling?
>
> I'm not sure what you are asking.
>
> If you have a 1 MHz carrier with 1 KHz of bandwidth,
> you might do something like sample at 10 KHz so
> your anti-alias filter has some room to work with.
> Then you feed the signal into a FFT and throw away
> the buckets that the filter didn't get rid of.
>
> You often pick the sampling frequency so the FFT
buckets
> (after aliasing) come out on convenient numbers.
>
> If by "baseband" you mean the raw signal between 0
and X,
> there isn't any information between 0 and X-tiny in a
typical
> narrow band modulated signal.
>
> If you are doing the aliasing trick, the
anti-aliasing filter
> has to block the baseband junk (noise) or it will get
into the
> A/D and confuse things. It's the reverse of the
"normal" anti-alias
> filter that gets rid of the noise above the baseband
so it doesn't
> alias down and trash your signal.
>
> --
> The suespammers.org mail server is located in
California. So are all my
> other mailboxes. Please do not send unsolicited bulk
e-mail or unsolicited
> commercial e-mail to my suespammers.org address or
any of my other addresses.
> These are my opinions, not necessarily my employer's.
I hate spam.
>

Hal Murray

December 26th 05, 07:23 AM

>The point is the sampling rate has to be done at just
>over double the frequency of the signal and not the
>bandwidth.

I'm sorry that I'm not smart enough to describe it in a way
that you can understand.

Maybe if you google for software-radio you will find something
that explains it in a way that makes sense.

--
The suespammers.org mail server is located in California. So are all my
other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's. I hate spam.

Rich Grise, but drunk

December 27th 05, 12:52 AM

On Sun, 25 Dec 2005 17:50:50 +1100, George Ghio wrote:

On Sun, 25 Dec 2005 17:50:50 +1100, George Ghio top-posted:

> I'll pay that. Thank you for the correction. Spent too many hours under
> the car, I guess.
>

Just out of curiosity, is top-posting de rigeur on the
rec.ovulation.awning NG? Someone has crossposted this to sci.erectionics.
desire, and the convention there is to bottom- or mid- (or interspersed- )
post.

Just wondering - the clsoest I've been to aviating is I logged 4 hrs.
worth of lessons in a C-150, and onec I sat in the Republic Airlines
DC-9 simulator - that was a trip! My only other associations with
aircarft other than as a passenter is that I worked at a place that sold
little tiiny 28V 40A PSUs, and I'd rather jump out of an airplane (with
a proper aprachute, of course), than try to land one. ;-)

Thanks!
Rich

> daestrom wrote:
>> "George Ghio" > wrote in message
>> ...
>>
>>>Yes this is the problem. While there are people who will tell you anything
>>>to make a sale, how do you know what you are really getting.
>>>
>>>One test is the "Modified Square Wave" test.
>>>
>>>When you hear these words you know you are dealing either with a shyster
>>>or an ignorant person who should not be selling things he does not
>>>understand.
>>>
>>
>>
>> Judging from your previous posts, I think you mean when you hear "Modified
>> *sine* wave", then you know you are dealing with shyster or an ignorant
>> person...."
>>
>> A salesperson that says their unit puts out a modified *square* wave would
>> be a sign[sic] of a knowledgable salesperson.
>>
>> daestrom
>>
>>

SolarFlare

December 27th 05, 01:56 AM

Which one do you have trouble reading?

"Rich Grise, but drunk" > wrote in
message
...
> Just out of curiosity, is top-posting de rigeur on
the
> rec.ovulation.awning NG? Someone has crossposted this
to sci.erectionics.
> desire, and the convention there is to bottom- or
mid- (or interspersed- )
> post.

[email protected]

December 27th 05, 07:16 AM

George Ghio wrote:
> wrote:
> > George Ghio wrote:

> >>I did build a kit inverter, once, years ago. It had a max rating of
> >>150W, Which it met.
> >>
> >>It had a half hour rating of 0W
> >>
> >>And a surge of about 300W

> > I'm still scratching my head over that one.

> Which part don't you understand

I didnt seriously think you were going to stand by the above specs.
Since you are, enough said.

NT

[email protected]

December 27th 05, 07:21 AM

wmbjk wrote:
> On 23 Dec 2005 23:57:27 -0800, wrote:
>
> >George Ghio wrote:
> >
> >> I did build a kit inverter, once, years ago. It had a max rating of
> >> 150W, Which it met.
> >>
> >> It had a half hour rating of 0W
> >>
> >> And a surge of about 300W
>
> >I'm still scratching my head over that one.
> >
> >
> >NT
>
> He previously wrote about using either a 150 Ohm rheostat (other times
> referred to as 150A or 200A), or 300k nichrome wire to control a few
> Amps of field current on a small 12V automotive alternator. According
> to the "designer" (who often refers to himself as a "solar power
> consultant"), 150 Ohms didn't allow sufficiently low output, hence the
> need for the nichrome wire. And as we all know, the prime
> consideration on a home-power generator is low output. <snorf> Similar
> wisdom surely underpins his other projects. For instance, liberal
> application of 300k wire might be useful when building a max 150, peak
> 300, zero Watt inverter, or most any zero Watt inverter for that
> matter. Perhaps strung around the property in large coils like razor
> wire at Slinky Manor. ;-)
>
> Wayne

:) The trouble is he may actually BE a solar consultant. Nothing
stopping him afaik. At least not for a few years anyway. :)

NT

Ray Andraka

December 27th 05, 04:08 PM

daestrom wrote:
> So, if I have a signal with a 1000 hz carrier, with a bandwidth of 50 hz,
> you think I can sample it at just 150 hz and get accurate reproduction?
> That's just wrong.
>
> It is the maximum frequency component in the signal that is important. The
> bandwidth is not related unless the lower edge of the band is at 0 hz
> (whereupon the upper side of the band is equal to the max frequency).
>
> daestrom
>
>
No, it is correct. If you have a signal with a 1000 Hz carrier and a 50
Hz Bandwidth, you can indeed sample it at 150 Hz and get accurate
reproduction...provided the rest of the spectrum is clear. That
requirement is typically provided with an anti-alias filter. In this
case, the anti-alias filter has to be a BAND-PASS filter centered on
1000 Hz rather than the low pass filter associated with baseband
sampling. This works because sampling folds the spectrum (aliasing) so
that parts of the frequency band with higher frequency than the sampling
frequency get folded back onto baseband. As long as the full spectrum
only has energy in a bandwidth less than or equal to half the sample
rate, you get all of the information necessary to reconstruct the
original signal (assuming you know the characteristics of the fixed
anti-alias filter so that you know which image to select when you unfold
the spectrum). If there was signal energy outside of the Fs/2
bandwidth, it adds to signal inside the bandwidth during the folding
that sampling causes, and then you lose information since there is no
way to separate the energy if it has been added with other energy by
folding.

Ray Andraka

December 27th 05, 04:10 PM

SolarFlare wrote:

> The point is the sampling rate has to be done at just
> over double the frequency of the signal and not the
> bandwidth.
>

No, that is not correct. It only needs to be sampled at > 2x the
bandwidth, assuming the spectrum has been properly filtered to energy
outside the signal of interest. See my earlier post.

Ray Andraka

December 27th 05, 04:23 PM

SolarFlare wrote:

> If only the baseband frequency is sampled at 6kHz then
> information is missing to recreate the original 100kHz
> and the sampling information is insufficient to
> recreate the original signal.
>
>
> This is analogous to saying the number 1234 can be
> represented by
> (1234-234) / 1000 = 1
>
> If I supply the number 1.0 you can regenerate the
> number 1234 from it? Not true, without the rest of the
> sampling information. The sample is incomplete.
>
> Bandwidth sampling only cannot recreate the original
> signal.
>

You've used the wrong part of 1234 for your example. The proper analogy
would be to say that 1234 can be represented by 234 in a 3 digit decimal
number system. In that case, the overflow caused by exceeding 999
results in 1234 aliasing onto 234. If you know that all your input
numbers are between 1000 and 1999, then 234 is sufficient information to
represent 1234 with no ambiguity.

The anti-alias filter on your sampling system performs the bracketing to
make sure that all the possible inputs are constrained to be within a
bandwidth of your center frequency +/- BW/2, so when sampled there is no
aliasing. In essence, that filter is the constraint that makes it work.

BTW, the same holds true for baseband sampling: The numbers in a
baseband system based on your example are assumed to be less than 1000,
so that 234 accurately represents 234. In that case if you put in 1234,
it would also map to 234 and you'd have an ambiguity. It just so
happens that in the baseband case, the representation is the same as the
original signal for signals within the bandwidth allowed by Fs/2. With
other than baseband, the representation is not the same as the number
represented, but the constraints imposed by the system allow you to
reconstruct the original value without ambiguity.

daestrom

December 27th 05, 10:49 PM

"Ray Andraka" > wrote in message
news:0Gdsf.34358$Mi5.34121@dukeread07...
> daestrom wrote:
>> So, if I have a signal with a 1000 hz carrier, with a bandwidth of 50 hz,
>> you think I can sample it at just 150 hz and get accurate reproduction?
>> That's just wrong.
>>
>> It is the maximum frequency component in the signal that is important.
>> The bandwidth is not related unless the lower edge of the band is at 0 hz
>> (whereupon the upper side of the band is equal to the max frequency).
>>
>> daestrom
>>
>>
> No, it is correct. If you have a signal with a 1000 Hz carrier and a 50
> Hz Bandwidth, you can indeed sample it at 150 Hz and get accurate
> reproduction...provided the rest of the spectrum is clear. That
> requirement is typically provided with an anti-alias filter. In this
> case, the anti-alias filter has to be a BAND-PASS filter centered on 1000
> Hz rather than the low pass filter associated with baseband sampling.
> This works because sampling folds the spectrum (aliasing) so that parts of
> the frequency band with higher frequency than the sampling frequency get
> folded back onto baseband. As long as the full spectrum only has energy
> in a bandwidth less than or equal to half the sample rate, you get all of
> the information necessary to reconstruct the original signal (assuming you
> know the characteristics of the fixed anti-alias filter so that you know
> which image to select when you unfold the spectrum). If there was signal
> energy outside of the Fs/2 bandwidth, it adds to signal inside the
> bandwidth during the folding that sampling causes, and then you lose
> information since there is no way to separate the energy if it has been
> added with other energy by folding.

You are in effect demodulating the incoming signal and sampling the result,
not sampling the incoming signal. You are 'throwing away' the information
that would tell you what the carrier freq is.

Now, in radio that may be all well and good, since demodulation is a
necessary part of reception anyway. But some of us were talking about
reproducing the incoming signal, not stripping out the low freq component of
some carrier.

Note that if the carrier is an exact multiple of the sample rate, *then* an
unmodulated carrier will produce no 'alias' signal. But 150 doesn't go
evenly into 1000.

If you have a completely unmodulated 1000 hz signal, passed through a 50 hz
wide band-pass, centered around 1000 hz and sampled at 150 hz, your sampled
data is indistinguisable from that of a 25 hz signal. Even knowing the
band-pass filter's characteristic doesn't tell me if the carrier was
unmodulated 1000 hz, or if there was a true 30 hz signal modulating it.

daestrom

George Ghio

December 27th 05, 11:24 PM

Ah I see. Non compus mentis is your base state.

Let's See if we can clear up the story for you.

150W max continuous rating. Didn't think that would have been to hard to
glean from the post if someone knew how inverters are rated.

0W half hour rating. That would indicate that the inverter in question
does not, in fact, have a half hour rating.

300W surge.This means that the inverter will supply 300W for a couple of
seconds or less. Enough to start a small motor or a TV.

Sorry you are TSP.

wrote:
> George Ghio wrote:
>
wrote:
>>
>>>George Ghio wrote:
>
>
>>>>I did build a kit inverter, once, years ago. It had a max rating of
>>>>150W, Which it met.
>>>>
>>>>It had a half hour rating of 0W
>>>>
>>>>And a surge of about 300W
>
>
>>>I'm still scratching my head over that one.
>
>
>>Which part don't you understand
>
>
> I didnt seriously think you were going to stand by the above specs.
> Since you are, enough said.
>
>
> NT
>

Ray Andraka

December 28th 05, 02:53 AM

daestrom wrote:
> "Ray Andraka" > wrote in message
> news:0Gdsf.34358$Mi5.34121@dukeread07...
>
>>daestrom wrote:
>>
>>>So, if I have a signal with a 1000 hz carrier, with a bandwidth of 50 hz,
>>>you think I can sample it at just 150 hz and get accurate reproduction?
>>>That's just wrong.
>>>
>>>It is the maximum frequency component in the signal that is important.
>>>The bandwidth is not related unless the lower edge of the band is at 0 hz
>>>(whereupon the upper side of the band is equal to the max frequency).
>>>
>>>daestrom
>>>
>>>
>>
>>No, it is correct. If you have a signal with a 1000 Hz carrier and a 50
>>Hz Bandwidth, you can indeed sample it at 150 Hz and get accurate
>>reproduction...provided the rest of the spectrum is clear. That
>>requirement is typically provided with an anti-alias filter. In this
>>case, the anti-alias filter has to be a BAND-PASS filter centered on 1000
>>Hz rather than the low pass filter associated with baseband sampling.
>>This works because sampling folds the spectrum (aliasing) so that parts of
>>the frequency band with higher frequency than the sampling frequency get
>>folded back onto baseband. As long as the full spectrum only has energy
>>in a bandwidth less than or equal to half the sample rate, you get all of
>>the information necessary to reconstruct the original signal (assuming you
>>know the characteristics of the fixed anti-alias filter so that you know
>>which image to select when you unfold the spectrum). If there was signal
>>energy outside of the Fs/2 bandwidth, it adds to signal inside the
>>bandwidth during the folding that sampling causes, and then you lose
>>information since there is no way to separate the energy if it has been
>>added with other energy by folding.
>
>
> You are in effect demodulating the incoming signal and sampling the result,
> not sampling the incoming signal. You are 'throwing away' the information
> that would tell you what the carrier freq is.
>
> Now, in radio that may be all well and good, since demodulation is a
> necessary part of reception anyway. But some of us were talking about
> reproducing the incoming signal, not stripping out the low freq component of
> some carrier.
>
> Note that if the carrier is an exact multiple of the sample rate, *then* an
> unmodulated carrier will produce no 'alias' signal. But 150 doesn't go
> evenly into 1000.
>
> If you have a completely unmodulated 1000 hz signal, passed through a 50 hz
> wide band-pass, centered around 1000 hz and sampled at 150 hz, your sampled
> data is indistinguisable from that of a 25 hz signal. Even knowing the
> band-pass filter's characteristic doesn't tell me if the carrier was
> unmodulated 1000 hz, or if there was a true 30 hz signal modulating it.
>
> daestrom
>
>

The information that tells you the frequency of the carrier is not
discarded, but is partially implied by the system, just as it is with a
baseband system. Remember, sampling is essentially the mixing of the
signal with an impulse train, followed by a sample rate decimation
without any filtering. The choice of frequencies in this example are
unfortunate because there is in fact some interference between the
positive and negative frequency images of the original signal. When
dealing with real-only inputs, you need to be judicious in selecting the
sample frequency so that the frequency folding does not fold the
negative image (that is a reflection of the positive image and is always
present for a real signal) onto the positive image. Still, that doesn't
mean that the sample frequency has to be a sub-multiple of the carrier.
For example, 160 Hz sampling works (as does 210 Hz) with a 1000Hz
signal that has a 50Hz bandwidth because it puts both the positive and
negative frequency images into the sampled spectrum without overlap.
There is sufficient information there to reconstruct the original signal
if the center frequency of the anti-alias filter is known.

And yes, you are correct that the sampled signal is indistinguishable
from one which it aliases onto: but those other frequencies are not
present in the signal thanks to the anti-alias filter. The point is
that the anti-alias filter needn't be a low pass filter. It can be a
band pass filter as long as the bandwidth is less than half the sample
frequency. If the input signal is a real signal, there are additional
considerations to make sure that the postive and negative frequeyncy
images do not overlap when the spectrum is folded.

George Ghio

December 28th 05, 03:06 AM

George Ghio wrote:
> Ah I see. Non compus mentis is your base state.
>
> Let's See if we can clear up the story for you.
>
> 150W max continuous rating. Didn't think that would have been to hard to
> glean from the post if someone knew how inverters are rated.
>
> 0W half hour rating. That would indicate that the inverter in question
> does not, in fact, have a half hour rating.
>
> 300W surge.This means that the inverter will supply 300W for a couple of
> seconds or less. Enough to start a small motor or a TV.
>
> Sorry you are TSP.
>
> wrote:
>
>> George Ghio wrote:
>>
>>> wrote:
>>>
>>>> George Ghio wrote:
>>
>>
>>
>>>>> I did build a kit inverter, once, years ago. It had a max rating of
>>>>> 150W, Which it met.
>>>>>
>>>>> It had a half hour rating of 0W
>>>>>
>>>>> And a surge of about 300W
>>
>>
>>
>>>> I'm still scratching my head over that one.
>>
>>
>>
>>> Which part don't you understand
>>
>>
>>
>> I didnt seriously think you were going to stand by the above specs.
>> Since you are, enough said.
>>
>>
>> NT
>>

daestrom

December 29th 05, 10:52 PM

"Ray Andraka" > wrote in message
news:C7nsf.35562$Mi5.29016@dukeread07...
> daestrom wrote:
>> "Ray Andraka" > wrote in message
>> news:0Gdsf.34358$Mi5.34121@dukeread07...
>>
>>>daestrom wrote:
>>>
>>>>So, if I have a signal with a 1000 hz carrier, with a bandwidth of 50
>>>>hz, you think I can sample it at just 150 hz and get accurate
>>>>reproduction? That's just wrong.
>>>>
>>>>It is the maximum frequency component in the signal that is important.
>>>>The bandwidth is not related unless the lower edge of the band is at 0
>>>>hz (whereupon the upper side of the band is equal to the max frequency).
>>>>
>>>>daestrom
>>>>
>>>>
>>>
>>>No, it is correct. If you have a signal with a 1000 Hz carrier and a 50
>>>Hz Bandwidth, you can indeed sample it at 150 Hz and get accurate
>>>reproduction...provided the rest of the spectrum is clear. That
>>>requirement is typically provided with an anti-alias filter. In this
>>>case, the anti-alias filter has to be a BAND-PASS filter centered on 1000
>>>Hz rather than the low pass filter associated with baseband sampling.
>>>This works because sampling folds the spectrum (aliasing) so that parts
>>>of the frequency band with higher frequency than the sampling frequency
>>>get folded back onto baseband. As long as the full spectrum only has
>>>energy in a bandwidth less than or equal to half the sample rate, you get
>>>all of the information necessary to reconstruct the original signal
>>>(assuming you know the characteristics of the fixed anti-alias filter so
>>>that you know which image to select when you unfold the spectrum). If
>>>there was signal energy outside of the Fs/2 bandwidth, it adds to signal
>>>inside the bandwidth during the folding that sampling causes, and then
>>>you lose information since there is no way to separate the energy if it
>>>has been added with other energy by folding.
>>
>>
>> You are in effect demodulating the incoming signal and sampling the
>> result, not sampling the incoming signal. You are 'throwing away' the
>> information that would tell you what the carrier freq is.
>>
>> Now, in radio that may be all well and good, since demodulation is a
>> necessary part of reception anyway. But some of us were talking about
>> reproducing the incoming signal, not stripping out the low freq component
>> of some carrier.
>>
>> Note that if the carrier is an exact multiple of the sample rate, *then*
>> an unmodulated carrier will produce no 'alias' signal. But 150 doesn't
>> go evenly into 1000.
>>
>> If you have a completely unmodulated 1000 hz signal, passed through a 50
>> hz wide band-pass, centered around 1000 hz and sampled at 150 hz, your
>> sampled data is indistinguisable from that of a 25 hz signal. Even
>> knowing the band-pass filter's characteristic doesn't tell me if the
>> carrier was unmodulated 1000 hz, or if there was a true 30 hz signal
>> modulating it.
>>
>> daestrom
>>
>>
>
> The information that tells you the frequency of the carrier is not
> discarded, but is partially implied by the system, just as it is with a
> baseband system. Remember, sampling is essentially the mixing of the
> signal with an impulse train, followed by a sample rate decimation without
> any filtering. The choice of frequencies in this example are unfortunate
> because there is in fact some interference between the positive and
> negative frequency images of the original signal.

Actually, I kind of chose those numbers for that very reason ;-)

When
> dealing with real-only inputs, you need to be judicious in selecting the
> sample frequency so that the frequency folding does not fold the negative
> image (that is a reflection of the positive image and is always present
> for a real signal) onto the positive image. Still, that doesn't mean that
> the sample frequency has to be a sub-multiple of the carrier. For example,
> 160 Hz sampling works (as does 210 Hz) with a 1000Hz signal that has a
> 50Hz bandwidth because it puts both the positive and negative frequency
> images into the sampled spectrum without overlap. There is sufficient
> information there to reconstruct the original signal if the center
> frequency of the anti-alias filter is known.
>
> And yes, you are correct that the sampled signal is indistinguishable from
> one which it aliases onto: but those other frequencies are not present in
> the signal thanks to the anti-alias filter. The point is that the
> anti-alias filter needn't be a low pass filter. It can be a band pass
> filter as long as the bandwidth is less than half the sample frequency.
> If the input signal is a real signal, there are additional considerations
> to make sure that the postive and negative frequeyncy images do not
> overlap when the spectrum is folded.

So what you're saying is, *if* you know the carrier frequency and band-width
of the signal imposed on that carrier, you can design a system that will be
able to reproduce the imposed signal using a relatively low sample rate (low
when compared to the carrier frequency).

But if the carrier frequency changes, then you need to modify the sample
rate to avoid a lot of aliasing issues. So in radio reception, the sample
rate is adjusted along with tuning the receiver? Or is this done at the
intermediate frequency which is fixed so that sample rate adjustment is
fixed with the intermediate frequency? (do they even still use
superheterodyning in tuners?? ;-)

It's been a long time since I did any RF stuff. But A/D and D/A stuff at AF
and lower has been quite a passion for me for some time. And the basic
Nyquist hasn't changed.

daestrom

Joel Kolstad

December 30th 05, 01:04 AM

"daestrom" > wrote in message
...
> So what you're saying is, *if* you know the carrier frequency and band-width
> of the signal imposed on that carrier, you can design a system that will be
> able to reproduce the imposed signal using a relatively low sample rate (low
> when compared to the carrier frequency).

It's a litle more general than that -- you only need to know that your signal
lies inbetween some lower and upper frequencies and that bandwidth is
(generally) less than 1/2 of the sample rate of the ADC.

> But if the carrier frequency changes, then you need to modify the sample
> rate to avoid a lot of aliasing issues.

Assuming all the "information" (the carrier and whatever sideband(s) you care
about) is still within your bandpass frequencies, you've lost nothing and
there is no aliasing with any non-zero signals.

> So in radio reception, the sample rate is adjusted along with tuning the
> receiver?

Not usually, although there are so many ways to build 'a radio,' I'm sure this
approach has been implemented at some point in time.

It pretty common to digitize significantly more of a radio band than the
bandwidth of the signal you're interested in and then just digitally track &
demodulate the one signal you need from the many that are present. This is
popular because none of the 'fundamental' settings of the system (local
oscillator frequencies, IF frequencies, ADC sample rate, anti-alias filters,
etc.) change; this makes the architecture inexpensive and highly flexible.
The downside is that sensitivity can be poor if there are other, stronger
sides in the band that you've digitized but aren't really interested in... A
common fix for this problem is to stick an adjustable notch filter somewhere
in the analog path, but of course that adds cost again... etc, etc, etc... we
sit around all day making these tradeoffs. :-) Another common fix is to
switch to frequency hopping spread spectrum modulation like Bluetooth uses.
(From a certain point of view, people like the cell phone carriers have it
easy in that they _own_ the spectrum they're operating in and know _exactly_
what signals should be present, their power levels, etc. -- That makes their
radio designs noticeably simpler and cheaper than "general purpose" wideband
receivers that are used by, e.g., the military, hams, etc.)

> Or is this done at the intermediate frequency which is fixed so that sample
> rate adjustment is fixed with the intermediate frequency?

This is quite common.

> (do they even still use superheterodyning in tuners?? ;-)

Superheterodyning is still common to get the RF down to an IF that can be
digitized directly. As Ray mentioned earlier, the problem with trying to
digitize, say, a narrowband 900MHz signal using a 5Msps ADC is that the effect
of any clock jitter going into the ADC gets multiplied by the 900/5, so at
some point obtaining a decent oscillator becomes impractically expensive.

---Joel

SolarFlare

December 30th 05, 01:05 AM

OK let's go with your analogy example of 1234 being
represnted by 234 only.

You have no way of decoding 234 into 1234 without
passing information of 1000 as your baseband info and
therefore the the number 1234 has not been successfuly
representedm as being reproduced without further
information.

Now we could further argue algorythms as part of the
information or part of the sample.

"Ray Andraka" > wrote in message
news:WUdsf.34360$Mi5.17847@dukeread07...
> You've used the wrong part of 1234 for your example.
The proper analogy
> would be to say that 1234 can be represented by 234
in a 3 digit decimal
> number system. In that case, the overflow caused by
exceeding 999
> results in 1234 aliasing onto 234. If you know that
all your input
> numbers are between 1000 and 1999, then 234 is
sufficient information to
> represent 1234 with no ambiguity.
>

SolarFlare

December 30th 05, 01:06 AM

Your sampling of only the bandwidth information is not
complete for decoding.

"Ray Andraka" > wrote in message
news:zIdsf.34359$Mi5.7331@dukeread07...
> SolarFlare wrote:
>
> > The point is the sampling rate has to be done at
just
> > over double the frequency of the signal and not the
> > bandwidth.
> >
>
>
> No, that is not correct. It only needs to be sampled
at > 2x the
> bandwidth, assuming the spectrum has been properly
filtered to energy
> outside the signal of interest. See my earlier post.

SolarFlare

December 30th 05, 01:46 AM

Now you have to provide samples ***AND*** changing
information with an algorthm to decode successfully.
Your samples are then not complete and useless without
other information supplied.

Superhetrodyning in a radio assumes a variable
superhetrodyning frequency when it gets decoded

Let's see you regenerate the original carrier and
information from that without the carrier frequency
known.

When you listen to the audio on your radio can you tell
the carrier frequency without the dial?

"Joel Kolstad" > wrote in
message ...
> Assuming all the "information" (the carrier and
whatever sideband(s) you care
> about) is still within your bandpass frequencies,
you've lost nothing and
> there is no aliasing with any non-zero signals.

> Superheterodyning is still common to get the RF down
to an IF that can be
> digitized directly. As Ray mentioned earlier, the
problem with trying to
> digitize, say, a narrowband 900MHz signal using a
5Msps ADC is that the effect
> of any clock jitter going into the ADC gets
multiplied by the 900/5, so at
> some point obtaining a decent oscillator becomes
impractically expensive.
>
> ---Joel
>
>

Joel Kolstad

December 30th 05, 03:41 AM

"SolarFlare" > wrote in message
...
> Now you have to provide samples ***AND*** changing
> information with an algorthm to decode successfully.
> Your samples are then not complete and useless without
> other information supplied.

This is true, but it's pretty much true for all communication systems, not
just sub-sampled digital ones. What changes is that sometimes the extra
'information' supplied can be done by something as sophisticated as a human's
brain as he tunes across the dial to find the 'best' sound -- this
corresponding to finding the carrier. (At some point this becomes a very
philosophical discussion... 'information' only has _meaning_ to an observer
who presumably knows something about or has a hunch as to what they're
observing is. Although one can compute the 'information' within signal in an
attempt to ascertain whether it resembles a random process or whether it's
conveying what we may 'intelligence.' Hence you can probably recognize the
difference between someone speaking random jibberish and an actual language
even without knowing that language, but on the other hand a good way to
conceal information is to make it appear almost completely random -- when in
fact it isn't --, which is exactly what cryptography does.)

> Let's see you regenerate the original carrier and
> information from that without the carrier frequency
> known.

Example: Take an antenna that's about a meter long... feed its output to an
LNA and then a reasonably steep bandpass filter passing 144-148MHz... sample
with a 16 bit, 12MSps ADC (I chose 12 just because it shifts 144MHz to
baseband, although there's no reason you can't use any frequency >8Msps).
Feed this digital word to a 16 bit DAC clocked at 10MSps. Lowpass filter the
DAC's output with a reasonably steep 4MHz low-pass filter. Feed this signal
to one port of a mixer and 144MHz to the other port. Poof! There's your
original signal back again! Feed this through another 144-148MHz bandpass
filter if you don't like the image response at 140-144MHz.

There are a few caveats here:

1) Clock jitter will tend to broaden out the specctra of the original signals
a bit (how good is your clock?)
2) The track & hold (analog) circuitry in the ADC has to be good to a couple
hundred MHz to avoid distortion.
3) Your noise floor is limited to no better than ~-100dB (and potentially
_much_ worse if you haven't been careful in your layout, power supply
decoupling, etc.). Note that everything described above also applies to
switched capacitor circuits (a technology whose time has just about passed,
but a neat idea); in that case analog noise rather than quantization noise
will dictate the noise floor (and realistically it'll probably be much worse
than -100dB...)
4) A typical DAC holds its output (e.g., a first-order hold) rather than
generating impulses, so the spectrum reproduced has a sin(x)/x profile to it
(frequencies closer to 148MHz will have less gain than those at 144MHz); this
can be fixed in the digital domain with the use of a FIR or IIR filter. In
some systems the droop is small enough that people just ignore it.

This example is reasonably practical. Strictly speaking, to make it simlper
you can just bandpass filter the output of the DAC directly and be OK, but the
sin(x) profile along with the limited analog bandwidth of the DAC tend to make
this approach impractical (you end up with very little SNR); this approach if
often used for proof-of-concept demos, though.

If you happen to have a carrier at 146.23MHz in the input signal, it'll most
certainly still be there in the output signal, yet the system didn't have to
'know' where the carrier was.

> When you listen to the audio on your radio can you tell
> the carrier frequency without the dial?

Sure, I can measure it! In fact, a much more interesting problem is how one
generates a carrier when none exists in the first place. There are plenty of
modulation schemes out there specifically don't use a carrier to either save
power (TV transmissions -- which have a very small albeit not eliminated
carrier -- are a good example of this) or to conceal transmissions (in
military systems nothing attracts unwanted attention more than a carrier some
60dB above the noise floor).

---Joel

Ray Andraka

December 30th 05, 04:10 PM

daestrom wrote:

>
> So what you're saying is, *if* you know the carrier frequency and band-width
> of the signal imposed on that carrier, you can design a system that will be
> able to reproduce the imposed signal using a relatively low sample rate (low
> when compared to the carrier frequency).
>
> But if the carrier frequency changes, then you need to modify the sample
> rate to avoid a lot of aliasing issues. So in radio reception, the sample
> rate is adjusted along with tuning the receiver? Or is this done at the
> intermediate frequency which is fixed so that sample rate adjustment is
> fixed with the intermediate frequency? (do they even still use
> superheterodyning in tuners?? ;-)
>
> It's been a long time since I did any RF stuff. But A/D and D/A stuff at AF
> and lower has been quite a passion for me for some time. And the basic
> Nyquist hasn't changed.
>
> daestrom
>
>

The carrier frequency has nothing to do with it. What is important is
the bandwidth and the center frequency of the pass-band. Note that your
signal needn't take up the whole bandwidth, and in a typical radio
system the signal you are tuning to is a very small fraction of the
pass-band. In any case, the pass band is defined by the anti-alias
filter, so practically speaking, it is a fixed, known pass band.
Therefore your *if* is satisfied.

What subsampling buys you is a way to sample an IF that is at a higher
frequency than the sample rate of your system, which may be limited
either by the ADC or by your computational power.

BTW, I never said nyquist changed. I was simply stating that it is more
general than the commonly held belief that the sample rate has to be at
least 2x the highest frequency. The truth is, the sample rate has to be
at least 2x the bandwidth of the signal.

Ray Andraka

December 30th 05, 04:30 PM

SolarFlare wrote:

> OK let's go with your analogy example of 1234 being
> represnted by 234 only.
>
> You have no way of decoding 234 into 1234 without
> passing information of 1000 as your baseband info and
> therefore the the number 1234 has not been successfuly
> representedm as being reproduced without further
> information.
>
> Now we could further argue algorythms as part of the
> information or part of the sample.
>
>

Likewise, you have no way of discerning 234 is actually 234 and not 1234
with a 3 digit decimal number system. The problem is not unique to
sub-sampling, it exists at baseband as well. The only difference is
that at baseband the representation looks the same as the signal. In
either case, you need to know the fixed constraints of the system to
fully comprehend the meaning of the representation. For example, in a 3
decimal digit system, you have no way of knowing that 234 really is 234
and not 1234 or 2234 unless you also know that the inputs are limited to
the range 0 to 999. The only way around that is to have an infinite
number of "symbols" to represent all the possible data when the set of
possible data is infinite. As soon as that set is not infinite, we can
take advantage of our knowledge of the system to reduce the set of
symbols to a manageable number of elements. I'd argue that any
engineering requires a set of implied constraints in order to make the
problem solvable.

In the case of the subsampling, we know by design what the pass-band of
the anti-alias filter is. That is a constant parameter designed into
the system, so presumably it is know to designers of all the components
of the system.

In the example case, then, we set as a system constraint the fact that
all inputs are in the range of 1000 to 1234. That constraint is a
constant, and is implied by the design. No information is lost by not
transmitting the constant that is already known throughout the system.
Doing so simply wastes bandwidth on your communications channel.

Richard Henry

December 30th 05, 10:28 PM

"Ray Andraka" > wrote in message
news:wZctf.58905$4l5.50283@dukeread05...
> daestrom wrote:
>
> >
> > So what you're saying is, *if* you know the carrier frequency and
band-width
> > of the signal imposed on that carrier, you can design a system that will
be
> > able to reproduce the imposed signal using a relatively low sample rate
(low
> > when compared to the carrier frequency).
> >
> > But if the carrier frequency changes, then you need to modify the sample
> > rate to avoid a lot of aliasing issues. So in radio reception, the
sample
> > rate is adjusted along with tuning the receiver? Or is this done at the
> > intermediate frequency which is fixed so that sample rate adjustment is
> > fixed with the intermediate frequency? (do they even still use
> > superheterodyning in tuners?? ;-)
> >
> > It's been a long time since I did any RF stuff. But A/D and D/A stuff
at AF
> > and lower has been quite a passion for me for some time. And the basic
> > Nyquist hasn't changed.
> >
> > daestrom
> >
> >
>
> The carrier frequency has nothing to do with it. What is important is
> the bandwidth and the center frequency of the pass-band. Note that your
> signal needn't take up the whole bandwidth, and in a typical radio
> system the signal you are tuning to is a very small fraction of the
> pass-band. In any case, the pass band is defined by the anti-alias
> filter, so practically speaking, it is a fixed, known pass band.
> Therefore your *if* is satisfied.
>
> What subsampling buys you is a way to sample an IF that is at a higher
> frequency than the sample rate of your system, which may be limited
> either by the ADC or by your computational power.
>
> BTW, I never said nyquist changed. I was simply stating that it is more
> general than the commonly held belief that the sample rate has to be at
> least 2x the highest frequency. The truth is, the sample rate has to be
> at least 2x the bandwidth of the signal.

After proper filtering of the input.

SolarFlare

December 31st 05, 02:38 AM

You still had to supply the constraints so the sampling
is not complete for any waveform.

This is like supplying $234 to buy that big screen TV
when you have to supply $1000 under the table to
actualy get it delivered. All the money is not upfront
and the $234 is a lie.

"Ray Andraka" > wrote in message
news:2gdtf.58906$4l5.30943@dukeread05...
> SolarFlare wrote:
>
> > OK let's go with your analogy example of 1234 being
> > represnted by 234 only.
> >
> > You have no way of decoding 234 into 1234 without
> > passing information of 1000 as your baseband info
and
> > therefore the the number 1234 has not been
successfuly
> > representedm as being reproduced without further
> > information.
> >
> > Now we could further argue algorythms as part of
the
> > information or part of the sample.
> >
> >
>
> Likewise, you have no way of discerning 234 is
actually 234 and not 1234
> with a 3 digit decimal number system. The problem is
not unique to
> sub-sampling, it exists at baseband as well. The
only difference is
> that at baseband the representation looks the same as
the signal. In
> either case, you need to know the fixed constraints
of the system to
> fully comprehend the meaning of the representation.
For example, in a 3
> decimal digit system, you have no way of knowing that
234 really is 234
> and not 1234 or 2234 unless you also know that the
inputs are limited to
> the range 0 to 999. The only way around that is to
have an infinite
> number of "symbols" to represent all the possible
data when the set of
> possible data is infinite. As soon as that set is
not infinite, we can
> take advantage of our knowledge of the system to
reduce the set of
> symbols to a manageable number of elements. I'd
argue that any
> engineering requires a set of implied constraints in
order to make the
> problem solvable.
>
> In the case of the subsampling, we know by design
what the pass-band of
> the anti-alias filter is. That is a constant
parameter designed into
> the system, so presumably it is know to designers of
all the components
> of the system.
>
> In the example case, then, we set as a system
constraint the fact that
> all inputs are in the range of 1000 to 1234. That
constraint is a
> constant, and is implied by the design. No
information is lost by not
> transmitting the constant that is already known
throughout the system.
> Doing so simply wastes bandwidth on your
communications channel.