Homebuilts and radios!

Hi, I am finishing the construction of a J-3. I intend to have the
following in the aircraft and would like to know if you can give me any
hints or suggestions on the type, location and mounting of the antenna
farm. I would either like to hide the antennas or build them from
scratch or kit. I am not sure what the uv protection on the fabric
would do to the signals if I use hidden antennas. The wing spars and ribs
are wood, and I plan to use Polyfiber to cover it.

I will have one of each of the following;

Microaire Comm
Microaire Transponder
PDA GPS System ( Would prefer built in system, but they are not in the
price range)
ELT
2-meter ham unit
Amateur TV Transmitter

Thanks

[Stealth Pilot]

On Wed, 22 Sep 2004 21:43:17 -0400, > wrote:

>Hi, I am finishing the construction of a J-3. I intend to have the
>following in the aircraft and would like to know if you can give me any
>hints or suggestions on the type, location and mounting of the antenna
>farm. I would either like to hide the antennas or build them from
>scratch or kit. I am not sure what the uv protection on the fabric
>would do to the signals if I use hidden antennas. The wing spars and ribs
>are wood, and I plan to use Polyfiber to cover it.
>
>I will have one of each of the following;
>
>Microaire Comm
>Microaire Transponder
>PDA GPS System ( Would prefer built in system, but they are not in the
>price range)
>ELT
>2-meter ham unit
>Amateur TV Transmitter
>
>Thanks
>

what no twin overhead foxtails?
:-)
Stealth Pilot

[sidk]

I can offer a word of advice regards the Microaire Comm: I have one
in my Starduster that now works quite well but initially I was plagued
with howling in the transmit audio due to rf getting back into the
radio because of two deficiencies in my installation:
1) non-optimum match to the transmit antenna.
2) insufficient shielding of audio wiring.

After I did it right, it works great.

Sid Knox

Velocity N199RS
Starduster N666SK
KR2 N24TC
W7QJQ

> Hi, I am finishing the construction of a J-3. I intend to have the
> following in the aircraft and would like to know if you can give me any
> hints or suggestions on the type, location and mounting of the antenna
> farm. ;
>
> Microaire Comm
> Microaire Transponder
> PDA GPS System ( Would prefer built in system, but they are not in the
> price range)
> ELT
> 2-meter ham unit
> Amateur TV Transmitter

[Craig]

> wrote in message >...
> I will have one of each of the following;
>
> Microaire Comm
> Microaire Transponder
> PDA GPS System ( Would prefer built in system, but they are not in the
> price range)
> ELT
> 2-meter ham unit
> Amateur TV Transmitter


Ahhh...small but not insignificant question here.....have you taken
the time to do a power loading analysis? Most Cubs that I know of
don't have either the battery or generator capacity to that much of a
load for any length of time.
Just for a data point, my Motorola VHF rig is 45 watt minimum, but
requires a 30 amp breaker.

Craig C.

[UltraJohn]

>
> Ahhh...small but not insignificant question here.....have you taken
> the time to do a power loading analysis? Most Cubs that I know of
> don't have either the battery or generator capacity to that much of a
> load for any length of time.
> Just for a data point, my Motorola VHF rig is 45 watt minimum, but
> requires a 30 amp breaker.
>
> Craig C.
>


What is it a tube type final? 45 watt should only require about 60 watt
input for the final plus maybe another 20 watt for the rest of the rig
including drivers (if it's transistor). That's less than 7 amps give it at
least 50% cushion would be around 10 amps so why 3 times the current for
the breaker?
John

[Craig]

UltraJohn > wrote in message >...

>
>
> What is it a tube type final? 45 watt should only require about 60 watt
> input for the final plus maybe another 20 watt for the rest of the rig
> including drivers (if it's transistor). That's less than 7 amps give it at
> least 50% cushion would be around 10 amps so why 3 times the current for
> the breaker?

Sorry for taking so long but I've had all the systems down due to some
ISP induced problems for the last few days.

Doubt it's a tube final (Motorola MCX1000), but I did take a better
look at the power cord this morning as I was getting ready to fab a
new mount for the van for it. Has a 3 amp control line and a 15 amp
main power line. The 30 amp line was a feed for some other gear for
the truck and just happened to be laying on the wire bundle when I
looked at it last week,

Craig C.

[John]

Craig wrote:

> UltraJohn > wrote in message
> >...
>
>>
>>
>> What is it a tube type final? 45 watt should only require about 60 watt
>> input for the final plus maybe another 20 watt for the rest of the rig
>> including drivers (if it's transistor). That's less than 7 amps give it
>> at least 50% cushion would be around 10 amps so why 3 times the current
>> for the breaker?
>
> Sorry for taking so long but I've had all the systems down due to some
> ISP induced problems for the last few days.
>
> Doubt it's a tube final (Motorola MCX1000), but I did take a better
> look at the power cord this morning as I was getting ready to fab a
> new mount for the van for it. Has a 3 amp control line and a 15 amp
> main power line. The 30 amp line was a feed for some other gear for
> the truck and just happened to be laying on the wire bundle when I
> looked at it last week,
>
> Craig C.
>
I can accept that a lot easier ;-) Still quite a bit overkill so trying to
figure out what kind of electrical system capacity to power it along with
all the other gear in the plane I think you could figure a lot less.
Have a great day
John
kc5vb (but mostly inactive (got into it to tinker with electronics which is
both my hobby and profession!))

[Robert Bonomi]

In article >,
John > wrote:
>Craig wrote:
>
>> UltraJohn > wrote in message
>> >...
>>
>>>
>>>
>>> What is it a tube type final? 45 watt should only require about 60 watt
>>> input for the final plus maybe another 20 watt for the rest of the rig
>>> including drivers (if it's transistor). That's less than 7 amps give it
>>> at least 50% cushion would be around 10 amps so why 3 times the current
>>> for the breaker?
>>
>> Sorry for taking so long but I've had all the systems down due to some
>> ISP induced problems for the last few days.
>>
>> Doubt it's a tube final (Motorola MCX1000), but I did take a better
>> look at the power cord this morning as I was getting ready to fab a
>> new mount for the van for it. Has a 3 amp control line and a 15 amp
>> main power line. The 30 amp line was a feed for some other gear for
>> the truck and just happened to be laying on the wire bundle when I
>> looked at it last week,
>>
>> Craig C.
>>
>I can accept that a lot easier ;-) Still quite a bit overkill so trying to
>figure out what kind of electrical system capacity to power it along with
>all the other gear in the plane I think you could figure a lot less.
>Have a great day
>John
>kc5vb (but mostly inactive (got into it to tinker with electronics which is
>both my hobby and profession!))
>

Part of it is probably due to the fact that Motorola rigs are well known
for actual RF output _well_ above the 'nominal' output. I used to use a
nominal 30 watt VHF hi-band unit where the actual RF out was just over 47
watts. Every time I took it into the radio shop to have the cavities tweaked,
they insisted on doing a TX test. *Despite* my warning them about the output
level, they'd blow the attenuator on the test instrument every time. After
the puff of smoke, the urge to say "I told you so" was nearly overwhelming. :)

[sidk]

> John > wrote:
> >Craig wrote:

> Part of it is probably due to the fact that Motorola rigs are well known
> for actual RF output _well_ above the 'nominal' output. I used to use a
> nominal 30 watt VHF hi-band unit where the actual RF out was just over 47
> watts. Every time I took it into the radio shop to have the cavities tweaked,
> they insisted on doing a TX test. *Despite* my warning them about the output
> level, they'd blow the attenuator on the test instrument every time. After
> the puff of smoke, the urge to say "I told you so" was nearly overwhelming. :)

Uhh, John... 47 Watts is barely 2 dB greater power than 30 Watts.
Are you saying that they had a piece of equipment that could not
handle a 2 dB overload and would "...blow the attenuator on the test
instrument every time." ???
Further, an attenuator designed for a nominal 30 Watts would have a
fairly substantial mass or a lot of forced-air cooling. An additional
2 dB would make it go up in a "...puff of smoke.." ???

Sid Knox

Velocity N199RS
Starduster N666SK
KR2 N24TC
W7QJQ

[John]

First Sid
Look closer at the post I was not the one making the post about the
attenuator. I made the post about the amps/power consumption of the unit.
The original poster made the att. comments. These threads can be confusing
at times!
;-)

That being said your answer is YES it could. Especially if the unit was run
for too long a time the equipment could be designed to handle continuous
power of 30 watts but the 47 watts would cause thermal runaway and
eventually burn it up. Also with a 50 ohm circuit and 47 watts the output
would be 48 volts rf, with 30 watts it would have 30 volts. I the unit had
voltage sensitive devices in it between those two voltages it could very
well pop it immediately.
So Craig could be giving you the correct skinny (or he could be blowing
smoke (pun intended)) you really would have to know the spec's of the
equipment to know for sure.
John





sidk wrote:

>> John > wrote:
>> >Craig wrote:
>
>> Part of it is probably due to the fact that Motorola rigs are well known
>> for actual RF output _well_ above the 'nominal' output. I used to use a
>> nominal 30 watt VHF hi-band unit where the actual RF out was just over 47
>> watts. Every time I took it into the radio shop to have the cavities
>> tweaked,
>> they insisted on doing a TX test. *Despite* my warning them about the
>> output
>> level, they'd blow the attenuator on the test instrument every time.
>> After the puff of smoke, the urge to say "I told you so" was nearly
>> overwhelming. :)
>
> Uhh, John... 47 Watts is barely 2 dB greater power than 30 Watts.
> Are you saying that they had a piece of equipment that could not
> handle a 2 dB overload and would "...blow the attenuator on the test
> instrument every time." ???
> Further, an attenuator designed for a nominal 30 Watts would have a
> fairly substantial mass or a lot of forced-air cooling. An additional
> 2 dB would make it go up in a "...puff of smoke.." ???
>
> Sid Knox
>
> Velocity N199RS
> Starduster N666SK
> KR2 N24TC
> W7QJQ

[Bushy]

Probably a 5 watt dummy load. Even my 15 watt one will handle 50 watts for a
couple of minutes.

Peter

[Craig]

John > wrote in message >...


a bunch snipped from here....



> So Craig could be giving you the correct skinny (or he could be blowing
> smoke (pun intended)) you really would have to know the spec's of the
> equipment to know for sure.
> John
>
>
>
'Cept it wasn't me talking about smoking equipment..... :) I haven't
smoked a piece of test gear other than a couple of Simpson VOM's since
getting out of tech school in '81.

Craig C.