iPhone in a glider?

Alan wrote:
In article %K%Ak.553$8v5.378@trnddc01 Eric Greenwell
writes:

More phones means the cells have to be smaller. Many/most of towers
around here have a number of what appear to be VERY directional
antennas, and the towers are low ( 100'), and surely very low
power, because the next tower is only a mile or two away. They
aren't going to reach out to 5 miles, even under the best of
conditions.

On the ground, where there are obstacles, that is true. To an
airborne receiver, the range is much farther.

And yet, I can have good service on the ground, but poor or no service
in the air, over the same area. It's not about obstacles, but antenna
patterns, power, and how the system handles a phone that is reaching
multiple towers.


Don't be sure about that low power -- the directional antennas have a
fair amount of gain. The FCC allows 500 watts per channel of
effective radiated power, but 100 watts is a more common figure.
(See: http://www.fcc.gov/cgb/consumerfacts/rfexposure.html ).

From the article:

"the majority of cellular or PCS cell sites in urban and suburban areas
operate at an ERP of 100 watts per channel or less".

The "or less" is important, as a small cell doesn't require much power.
The ERP is obtained with directional antennas, so while it might seem
high, the vertical angle coverage is very shallow. A cell set up for an
Interstate highway will have to use much more power as the cells are
farther apart, and the pattern might be broader, so aircraft near a
highway might experience better reception.


Even a very small amount of power to them will provide far more than
5 miles range.

In fact, one of the noted problems of GSM is that the timing of the
system is the timing induced range limit of about 25 miles, but an
extended variant increases this substantially. Fishermen off the
coast of the U.S. use cell phones out well past 25 miles.

And maybe a cell phone used in the air in those areas would work well.
It's not a place glider pilots have much experience with! THe coast is a
different situation than a inhabited area, and I'm guessing the antenna
power and pattern are likely quite different because of that.

I have used cellphones over 8 miles offshore, and apparently glider
pilots carry them in case of land outs in some pretty remote areas.

And with the full expectation that it will be pure luck if it works; for
example, my phone does not work on sections of major highways in Nevada,
so expecting to work in most areas off the highway is unwise. That is
why the SPOT device is becoming so popular, along with PLBs, in addition
to the usual ELTs and aviation radios. Also, pilots try to radio their
position while in air before landing, because they know using a cell
phone or aircraft radio on the ground is going to be unreliable.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4
* New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

On Sep 20, 1:22*am, John Smith wrote:
BTW, there is GeoPS, a Macintosh application for up and downloading data
from/to a logger. Wouter seems willing to port the app to the iPhone if
there is enough demand.

Have a look at his site and encourage him to do the port!http://www.human-software.nl/geops/

How will he port this if there is no serial port on the iPhone/iPod
Touch. (unless you want to jail break one and also provide RS-232 line
driver hardware). And you can't use a USB-serial adapter on an iPhone
like you would do on a Mac with this software since it is just a USB
slave.

Darryl

Wow-

Whatever happened to pure flying?


"Matt Herron Jr." wrote in message
...
Has anyone thought about applications for the iPhone 3G platform in a
glider? It has an excellent sunlight readable screen with touch
interface that causes no loss of image quality. It has an
accelerometer built in, a GPS that is probably better than spot,
wireless for speech commands, remote interfaces, etc. fast processor,
lots of ram for large maps and gesture recognition for panning,
zooming, etc. Web access (where available) for a quick weather update
before launch. Seems like an opportunity waiting to happen...

Come up with some good ideas, and maybe I will implement one!

Matt Herron
GlidePlan Inc.
http://www.glideplan.com

In article Eric Greenwell writes:
Alan wrote:
On the ground, where there are obstacles, that is true. To an
airborne receiver, the range is much farther.

And yet, I can have good service on the ground, but poor or no service
in the air, over the same area. It's not about obstacles, but antenna
patterns, power, and how the system handles a phone that is reaching
multiple towers.

My point exactly.

In the air, your phone hears multiple cell transmitters on each frequency.
It may have difficulty finding a channel where it can clearly hear the
control information.

On the ground, those obstacles limit the number of cell towers your phone
can hear, so it has no trouble finding a clean channel.


Don't be sure about that low power -- the directional antennas have a
fair amount of gain. The FCC allows 500 watts per channel of
effective radiated power, but 100 watts is a more common figure.
(See: http://www.fcc.gov/cgb/consumerfacts/rfexposure.html ).

From the article:

"the majority of cellular or PCS cell sites in urban and suburban areas
operate at an ERP of 100 watts per channel or less".

The "or less" is important, as a small cell doesn't require much power.
The ERP is obtained with directional antennas, so while it might seem
high, the vertical angle coverage is very shallow.

However, the vertical angle is not that shallow. Even an antenna with a
half power beamwidth extending up only 5 degrees puts that half power level
above 3000 feet at 7 miles out, a very easy range given the lack of
obstacles.

Directional antennas don't completely cut off outside the half power
beamwidth.

Your explanation also doesn't explain why when the cellphone doesn't work
while standing on the mountain top next to the suburban area, walking behind
a building to shield the phone from the view of so many cell towers causes it
to start working. The angles from the cell towers don't change.

Alan
wa6azp

In article John Smith writes:
Alan wrote:

Now, if you can tell where *you* are, and provide the links to the
regulations there, we can check if it is legal there.

I'm sorry but I can't, because there is no regulation at all here
regarding the use of cell phones in VFR aircraft.

Do you have regulations concerning radio transmission? Are they online?

Do you have any aircraft regulations? Are they online?

Where are you?

Alan

Alan wrote:
In article Eric Greenwell writes:

And yet, I can have good service on the ground, but poor or no service
in the air, over the same area. It's not about obstacles, but antenna
patterns, power, and how the system handles a phone that is reaching
multiple towers.

My point exactly.

In the air, your phone hears multiple cell transmitters on each frequency.
It may have difficulty finding a channel where it can clearly hear the
control information.

That sounds like a pretty good explanation. Would that explain why the
the signal strength display (number of bars shown) is low or zero? The
lack of bars is what makes me think the power drops off with altitude
enough to stop the phone from working, but maybe that's incorrect.

Your explanation also doesn't explain why when the cellphone doesn't work
while standing on the mountain top next to the suburban area, walking behind
a building to shield the phone from the view of so many cell towers causes it
to start working. The angles from the cell towers don't change.

I haven't tried that, but it does suggest the phone in the glider should
be shielded so it uses signals in only one direction as a way to improve
it's operation. Tough to do while circling, but maybe it'd be practical
in straight flight.


--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4
* New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

In article Eric Greenwell writes:
Alan wrote:
In article Eric Greenwell writes:

And yet, I can have good service on the ground, but poor or no service
in the air, over the same area. It's not about obstacles, but antenna
patterns, power, and how the system handles a phone that is reaching
multiple towers.

My point exactly.

In the air, your phone hears multiple cell transmitters on each frequency.
It may have difficulty finding a channel where it can clearly hear the
control information.

That sounds like a pretty good explanation. Would that explain why the
the signal strength display (number of bars shown) is low or zero? The
lack of bars is what makes me think the power drops off with altitude
enough to stop the phone from working, but maybe that's incorrect.


You are quite correct that in many cases, this indication is not real signal
strength.

Part of the problem with the count of bars on such devices is that the number
of bars is often derived from a "quality of signal" metric, such as error rate,
rather than the actual signal strength. Apparently that is easier to do in the
software of the phone. As such, interference can lower the number of bars just
as a weak signal can; unfortunately it can be hard to tell which is the problem
with the reception.

The same is true of most digital television receivers or converters. There
they even frequently label it as 'signal strength', when it most definitely
is not.

Another annoying feature of these digital indications is that the result is
fairly slow in updating. This makes it difficult to position a cellphone or
aim a television antenna.


Your explanation also doesn't explain why when the cellphone doesn't work
while standing on the mountain top next to the suburban area, walking behind
a building to shield the phone from the view of so many cell towers causes it
to start working. The angles from the cell towers don't change.

I haven't tried that, but it does suggest the phone in the glider should
be shielded so it uses signals in only one direction as a way to improve
it's operation. Tough to do while circling, but maybe it'd be practical
in straight flight.

Well, it would seem tight quarters for manuvering a good shield inside a
fiberglass glider, and using the body of the glider for that would probably
be ineffective. A metal glider might limit downward signals to those that
diffract over the body into the glider, but that could also be hard to
control.

If you can manage to do it, though, I would bet that it would work.


Alan
wa6azp

Alan wrote:
In article Eric Greenwell writes:
Well, it would seem tight quarters for manuvering a good shield inside a
fiberglass glider, and using the body of the glider for that would probably
be ineffective. A metal glider might limit downward signals to those that
diffract over the body into the glider, but that could also be hard to
control.

If you can manage to do it, though, I would bet that it would work.

I'll give it a try next time I fly. In the past, I've held the phone up
high in the cockpit so it good get a good view of the ground, which
worked well with my old analog/TDMA phone, but now that sounds like the
wrong thing to do.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4
* New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

On Sep 18, 12:32*am, "Matt Herron Jr." wrote:
Has anyone thought about applications for the iPhone 3G platform in a
glider? *It has an excellent sunlight readable screen with touch
interface that causes no loss of image quality. *It has an
accelerometer built in, a GPS that is probably better than spot,
wireless for speech commands, remote interfaces, etc. fast processor,
lots of ram for large maps and gesture recognition for panning,
zooming, etc. *Web access (where available) for a quick weather update
before launch. *Seems like an opportunity waiting to happen...

Come up with some good ideas, and maybe I will implement one!

Matt Herron
GlidePlan Inc.http://www.glideplan.com

What the hell, there are so many rules and regulations that the rule
makers are lost. I climb 9,000 ft mountains near a 16 million
population, and my phone will probably blast them all. I am not in an
aircraft, so I'm legal, but I might as well be. I fly over the same
mtns and would like to have the ability to have someone be able to
track my position by GPS. My granddaughter landed in the big nasty
mountains and spent the night in "God knew nowhere". She managed a
safe landing but search and rescue had to be called. If the highly
respected geniuses can create a thing like B Baum describes, surely
some one can figure that it would save lives and money in search and
rescue. Better than an ELT. Think about the search for Faucett last
year.
Let's pray that progress continues and is not stopped by some dumb ass
legislator that likes to make rules. F Robinson.

In article fredsez writes:

What the hell, there are so many rules and regulations that the rule
makers are lost. I climb 9,000 ft mountains near a 16 million
population, and my phone will probably blast them all. I am not in an
aircraft, so I'm legal, but I might as well be. I fly over the same
mtns and would like to have the ability to have someone be able to
track my position by GPS. My granddaughter landed in the big nasty
mountains and spent the night in "God knew nowhere". She managed a
safe landing but search and rescue had to be called. If the highly
respected geniuses can create a thing like B Baum describes, surely
some one can figure that it would save lives and money in search and
rescue. Better than an ELT. Think about the search for Faucett last
year.
Let's pray that progress continues and is not stopped by some dumb ass
legislator that likes to make rules. F Robinson.

The discussion included the concept that cellphones often do not work
on those mountains, or in gliders. Various folks had noticed this.
I notice this on a 2600 foot mountain, with far fewer than 16 million
population in sight.

Cell phones often don't work back in the mountains, or the valleys
between them. Look up the details of the family who got stuck in the
snow in southwestern Oregon a few years ago -- the cellphone did not
work, and one member of the family died trying to walk out. ( I think
that he should have (a) stayed with the family in the car, and (b) had
a way to recharge the cellphone. )

Banning cellphone use in aircraft is not some dumb legislator -- it
is the result of engineers knowledgable in the effects and principles
of cellphone systems. Banning them in cars while driving is dumb
legislators who don't understand real studies of safety...

If you want progress, use a satellite phone system that will work
anywhere you get a view of the sky. I think Spot is one such system.
Do not rely on cellular systems that have incomplete coverage.


Alan