iPhone in a glider?

In article Martin Gregorie writes:
On Fri, 19 Sep 2008 10:25:42 -0500, Michael Ash wrote:


Anyone know more about it? I'd like to know more than my patchwork
memory....

In the UK, anyway, the base station transmission patterns are quite flat
which can stop you getting a signal in the air.

A year or two back I wanted to annoy a friend with the "ring him and hold
phone by the audio vario" trick, but at 3000ft over Huntingdon, i.e.
above a flat bit of Cambridgeshire, there was no signal at all. I was
using a GSM phone, so the radiation pattern was evidently flat enough the
exclude not only Huntingdon masts but also those further away (Cambridge,
Northampton). This makes sense to me. Why should a telco waste
electricity transmitting a hemispherical pattern when a pancake pattern
will give a better signal strength for less radiated power throughout its
service area.


Interesting. Generally, the attenuation possible from an antenna depends
on the angle of elevation, and if you are 5 miles from the tower, at 3000
feet, you would be 6.5 degrees of elevation above horizontal, which should
be well within the pattern of the antenna. (Any reduction would be easily
made up by the very clear path to the tower.)

I have noticed the same effect on top of mountains here -- at 2600 feet
elevation, looking out at the populated areas, there is no signal.
HOWEVER --- If I walk away and hide behind a building, I get nice strong
signal.

There are a limited number of channels where the cell system
transmits control information. When the phone is not on a call, it
listens to one of them. Each cell site (tower) has one (or perhaps
more) channel for this control information. Like cell calls, it is not
re-used until a "safe" distance away.

When on top of a mountain, there are dozens of towers within sight.
Unfortunately, every available channel is in use by several of these
towers. Thus, the phone cannot receive a clear control signal on any
of the control channels -- each is a jumbled mess of several sites
transmitters.

Much the same happens in the glider.

Hiding behind the building, a few feet back from the edge of the
mountaintop blocks many of these signals. The phone found a good one,
and used it.


IIRC this has been noticed and commented on in the USA too.

And I strongly believe that the signal pattern of the antennas is not
the cause of the problem, or stepping a bit behind the building would not
have made the phone work, as the pattern would have been the same.


Alan

In article John Smith writes:
Alan wrote:

It might be fun, but it is also quite illegal.

47 cfr 22.925 states:

What the hell is 47 cfr 22.925???

The FAA prohibits the use in flight

And what the hell is FAA???

Oh, I see! You've just forgotten that there's life outside the USA.

No, I just quoted the rules where I am, and where a large number of
the participants are.

I did, however, forget for a moment that the iPhone is now available
out there, too.

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

Alan

On Sep 19, 9:07*pm, (Alan) wrote:
In article Darryl Ramm writes:

As pilot in command of a non-IFR flight I grant myself permission to
use all kinds of electronic toys in flight. So that gets rid of FAA
concerns.

* Sounds good. *It has long worked for me, too.

However my belief is that 47 CFR. 22.925 does apply to the
iPhone since it is quad-band GSM that uses the GSM 850MHz band in the
USA. If you have say a different brand PCS phone that exclusively uses
1800MHz then this would not apply to you.

* Perhaps not, because some call those PCS instead of cellphones, but I don't
know what the FCC's reaction would be. *I would not want to be explaining it
when they are pointing out some definition in another part of the rules that
says cell phone covers both...


The legal issue as I read it is only with "cellphones" that use the
800MHz spectrum - it is devices using this spectrum that is
specifically called out in the regulations. That is the only thing
covered by the FCC regulations we are talking about. I fully expect
the FCC to understand the difference say between GSM850 vs PCS1800.
But PCS in general, and especially factoring USA coverage, is much
less useful to try to use from the air. And when was the last time
anybody saw an FCC investigator hanging around the airport.

To me, cellphones don't work well enough in the air to hassle with and
can be distracting, so unless I really need to try to make a call I
keep it turned off. Which keeps the battery charged for when I might
need it after landing should I be lucky enough to have reception.


Darryl

Alan wrote:

A year or two back I wanted to annoy a friend with the "ring him and hold
phone by the audio vario" trick, but at 3000ft over Huntingdon, i.e.
above a flat bit of Cambridgeshire, there was no signal at all. I was
using a GSM phone, so the radiation pattern was evidently flat enough the
exclude not only Huntingdon masts but also those further away (Cambridge,
Northampton). This makes sense to me. Why should a telco waste
electricity transmitting a hemispherical pattern when a pancake pattern
will give a better signal strength for less radiated power throughout its
service area.


Interesting. Generally, the attenuation possible from an antenna depends
on the angle of elevation, and if you are 5 miles from the tower, at 3000
feet, you would be 6.5 degrees of elevation above horizontal, which should
be well within the pattern of the antenna. (Any reduction would be easily
made up by the very clear path to the tower.)

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. The loss of
signal at 3000' or so is common where the cells a small, such as near
cities. The rural areas often work to higher altitudes, if they have
coverage in the area.

My old analog/TDMA phone used to work very well to even 15000' agl, but
my new TMobile GSM phone is unreliable off the ground, and worthless at
our 7000-9000 agl soaring altitudes, even in our mostly rural Eastern
Washington.

I suspect there is a lot of variation between providers; even so, I
think it's just going to get worse as the cells get smaller yet.

--
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 %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.

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 ).

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.

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


Alan
wa6azp

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

I've already complained about lack of any way to communicate with an
external GPS but I'm enjoying this so lets bash this a bit more.

I'm not sure what a SPOT satellite messenger and a 3G iPhone GPS have
to do with each other but lets tackle that anyhow... The GPS in the
iPhone 3G is an Infineon PMB2525 Hammerhead II GPS with a really small
antenna (see http://blogs.zdnet.com/hardware/?p=2261&page=2). The
antenna will be facing the pilot if in a usual PDA type cradle, gee it
might work but it is not a good place for high quality GPS reception
in a glider.

The SPOT Messenger uses a - Nemerix NX2 GPS Chipset (maybe they've
upgraded to the NX3?) with a larger GPS antenna than the iPhone, and
it's antenna is on the top of the device so if placed as intended the
antenna will have a good view of the sky. Both chipsets are similar
and both are aimed at the same market of intelligent devices like
cellphones requiring low power consumption, both chipsets are amazing
for what they can do. So I'd disagree with the comment on the iPhone
GPS being better the SPOT. Not that the comparison is relevent. A
modern GPS receiver that I'd want to use in an aircraft for navigation
purposes with a traditional large antenna correctly oriented to the
sky should do much better than the iPhone GPS, but I'll point out that
many flight computers etc. are doing fine using very old GPS engines,
but it's the antenna location/orientation that can be really
important.

Then there is the CoreLocation API that the iPhone SDK exposes. I'd
not want to try to develop an aviation navigation package on top of
the rudimentary services it exposes. OK so you can get basic info
including altitude, but that's it. Want to look at any low level
settings or status like how many satellites are in view in, etc. you
are SOL. Oh yes and that pesky iPhone SDK agreement prohibits hacking
into any lower level (GPS) interfaces. And there is the supposed
blacklist/killswitch inside the CoreLocation API that allows Apple to
shut off acces to applications using that service they don't like. Try
to use this to navigate an aircraft (if they don't like the route
guidance part), try to bypass the App Store, they might still be able
to get you with the CoreLocation kill switch. So seems if you want to
go that far you might as well jailbreak the phone.

And I think somebody already mentioned that the internal GPS is turned
off when the phone is in Airplane mode. So you'll need to leave the
GSM phone on, violating that FCC rule, but more importantly sucking
power and putting out heat. So you'll definitely need to power the
iPhone from the ship's battery. I have no problem with that but wonder
how hot the iPhone will get in direct sunlight in a hot cockpit and
whether it will handle this any better than the two iPAQ 4700 I own
that suck when they get hot.

So where does that leave us? As I see it the iPhone is pretty piece of
jewelry that as it stands today is unlikely to be useful for a soaring
navigation/display unless you want to jailbreak and hack the phone and
I just don't see the effort/reward there. It is however a damn nice
iPod to take along on flights and handy for finding the nearest
steakhouse for that tired ground crew.

Darryl

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

I've tried to run XC Skies on mine, but it doesn't work very well.
I've even asked the guys at XC Skies to make an iPhone app, and they
said it was a great idea, but no app thus far.

On Sep 19, 11:24*pm, Darryl Ramm wrote:
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

I've already complained about lack of any way to communicate with an
external GPS but I'm enjoying this so lets bash this a bit more.

I'm not sure what a SPOT satellite messenger and a 3G iPhone GPS have
to do with each other but lets tackle that anyhow... The GPS in the
iPhone 3G is an Infineon PMB2525 Hammerhead II GPS with a really small
antenna (seehttp://blogs.zdnet.com/hardware/?p=2261&page=2). The
antenna will be facing the pilot if in a usual PDA type cradle, gee it
might work but it is not a good place for high quality GPS reception
in a glider.

The SPOT Messenger uses a - Nemerix NX2 GPS Chipset (maybe they've
upgraded to the NX3?) with a larger GPS antenna than the iPhone, and
it's antenna is on the top of the device so if placed as intended the
antenna will have a good view of the sky. *Both chipsets are similar
and both are aimed at the same market of intelligent devices like
cellphones requiring low power consumption, both chipsets are amazing
for what they can do. So I'd disagree with the comment on the iPhone
GPS being better the SPOT. Not that the comparison is relevent. A
modern GPS receiver that I'd want to use in an aircraft for navigation
purposes with a traditional large antenna correctly oriented to the
sky should do much better than the iPhone GPS, but I'll point out that
many flight computers etc. are doing fine using very old GPS engines,
but it's the antenna location/orientation that can be really
important.

Then there is the CoreLocation API that the iPhone SDK exposes. I'd
not want to try to develop an aviation navigation package on top of
the rudimentary services it exposes. OK so you can get basic info
including altitude, but that's it. Want to look at any low level
settings or status like how many satellites are in view in, etc. you
are SOL. Oh yes and that pesky iPhone SDK agreement prohibits hacking
into any lower level (GPS) interfaces. And there is the supposed
blacklist/killswitch inside the CoreLocation API that allows Apple to
shut off acces to applications using that service they don't like. Try
to use this to navigate an aircraft (if they don't like the route
guidance part), try to bypass the App Store, they might still be able
to get you with the CoreLocation kill switch. So seems if you want to
go that far you might as well jailbreak the phone.

And I think somebody already mentioned that the internal GPS is turned
off when the phone is in Airplane mode. So you'll need to leave the
GSM phone on, violating that FCC rule, but more importantly sucking
power and putting out heat. So you'll definitely need to power the
iPhone from the ship's battery. I have no problem with that but wonder
how hot the iPhone will get in direct sunlight in a hot cockpit and
whether it will handle this any better than the two iPAQ 4700 I own
that suck when they get hot.

So where does that leave us? As I see it the iPhone is pretty piece of
jewelry that as it stands today is unlikely to be useful for a soaring
navigation/display unless you want to jailbreak and hack the phone and
I just don't see the effort/reward there. It is however a damn nice
iPod to take along on flights and handy for finding the nearest
steakhouse for that tired ground crew.

Darryl

BTW Matt I meant to end my rant on a positive tone - a perfect iPhone
application example would be an iPhone friendly version of Dr Jack's
BLIPMAPS starting with a minimalistic website laid out for the iPhone
(I'm building my own simplified pages to get to Jack's files), going
through to an iPhone universal BLIPMAP viewer application, complete
with the ability to store (and recall in flight) things like RASP
convergence charts - things that actually are useful in flight. You
could use the crappy internal GPS to locate where you are located
within that viewer and provide track/heading up map orientation - but
you are not using it for primary navigation. I do use the iPhone now
to check RASP blipmaps before flying and the multi-touch interface is
just beautiful compared to tryign to do this on other mobile devices/
PDAs.


Darryl

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.

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/