Planes & Cell phones

[Greg Copeland]

Recentingly, in another thread, cell phones and planes came up. I
thought others might be interested in these links.

http://www.eweek.com/article2/0,1759,1568024,00.asp
http://wirelesscabin.com/
http://www.wired.com/wired/archive/12.04/start.html?pg=12

The general theory on modern cell phones in flight, goes like this:
The FCC also has a ban because when you're in flight, you're always at
least 6-8 miles away from the nearest cell tower. You end up communicating
with too many towers and bogging down the network. One or two such calls
is tolerable, but a whole plane load moving through would disrupt the
ground-based users of the network. Remember, the farther you are from a
tower, the more power your cell phone uses to communicate with it's tower;
up to 5-watts. Worse, a plane full of 5-watt transmitters causes
terrestrial interference problems for the land cell users, in a large
radius around the plane.

This picocell concept (covered the above links) solves both problems by
moving the nearest cell tower to just a few feet away from the phone.
Therefore, the phone kicks into its lowest power tx setting,
and never talks to any other tower. Of course, I don't think you can
expect on in a small GA plane anytime soon. ;)

I also found a quote that went like this:
"The restriction against cell phones is an FCC regulation and applies to
all aircraft that can fly over a certain speed (maybe 200 kts?). Quickly
switching cells during high speed flight causes all sorts of problems on
the cell network."

Can anyone confirm such an FCC regulation as it relates to airspeed? I
must admit, from I understand of the subject, it does make sense. Just
the same, confirmation would be great.

Lastly, can anyone confirm first hand accounts of cell phones actually
causing some type, instrumentation or radio interference?

At worst, hopefully this will be some food for thought.

Thanks! Cheers!

[David Brooks]

"Greg Copeland" > wrote in message
...
> Recentingly, in another thread, cell phones and planes came up. I
> thought others might be interested in these links.
>
> http://www.eweek.com/article2/0,1759,1568024,00.asp
> http://wirelesscabin.com/
> http://www.wired.com/wired/archive/12.04/start.html?pg=12
>
> The general theory on modern cell phones in flight, goes like this:
> The FCC also has a ban because when you're in flight, you're always at
> least 6-8 miles away from the nearest cell tower. You end up communicating
> with too many towers and bogging down the network. One or two such
calls...

Here's a needed clarification. Are there still problems when the phone isn't
making a call, but just sitting there listening to the network? I know such
a phone is continuously acquiring the next tower down the road. Would it be
true that the problem with passive phones is the same as with active ones,
but to a lesser extent?

-- David Brooks

[Dennis O'Connor]

I think you have too much time on your hands...
cheers ... denny

"Greg Copeland" > wrote in > At worst, hopefully this
will be some food for thought.
>
> Thanks! Cheers!
>
>

[Greg Copeland]

On Tue, 20 Apr 2004 12:21:33 -0700, David Brooks wrote:

> "Greg Copeland" > wrote in message
> ...
>> Recentingly, in another thread, cell phones and planes came up. I
>> thought others might be interested in these links.
>>
>> http://www.eweek.com/article2/0,1759,1568024,00.asp
>> http://wirelesscabin.com/
>> http://www.wired.com/wired/archive/12.04/start.html?pg=12
>>
>> The general theory on modern cell phones in flight, goes like this:
>> The FCC also has a ban because when you're in flight, you're always at
>> least 6-8 miles away from the nearest cell tower. You end up communicating
>> with too many towers and bogging down the network. One or two such
> calls...
>
> Here's a needed clarification. Are there still problems when the phone isn't
> making a call, but just sitting there listening to the network? I know such
> a phone is continuously acquiring the next tower down the road. Would it be
> true that the problem with passive phones is the same as with active ones,
> but to a lesser extent?
>
> -- David Brooks

Well, first let me say that I am NOT a subject matter expert on this, so
please, take my comments with a grain of salt. :)

When you speak of active versus passive, do you mean a phone being
actively used for calling versus a phone simply turned on? I'll assume
that's what you mean. A phone that is not actively particpating in a call is
still periodically attempting to locate it's best tower. It may be
sharing additional tidbits as well, I'm not sure. Nonetheless, if it's
transmitting, it's causing these problems. Like you, I suspect that it is
causing problems, just to a lessor extent.

If you have a phone, like mine, which periodically blinks, that blink
means it just transmitted. AFAIK, it's the fact that the phone is
transmitting, especially at 5-watts, that is causing some of the problems,
without regard for the content that is being transmitted. The fact that
you're traveling at a high rate of speed, probably causes more frequent
tower contacts (and tower hops) from your phone, however, that's purely
speculation on my part.

[Jay Honeck]

> I think you have too much time on your hands...
> cheers ... denny

Actually, I think it's a cool topic.

I'd be willing to fly slower than 200 knots if it meant I could legally use
my cell phone in the air!

:-)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[FUji]

>Greg Copeland" > wrote in message
...
<snip>
> The general theory on modern cell phones in flight, goes like this:
> The FCC also has a ban because when you're in flight, you're always at
> least 6-8 miles away from the nearest cell tower. You end up communicating
> with too many towers and bogging down the network. One or two such calls
> is tolerable, but a whole plane load moving through would disrupt the
> ground-based users of the network. Remember, the farther you are from a
> tower, the more power your cell phone uses to communicate with it's tower;
> up to 5-watts. Worse, a plane full of 5-watt transmitters causes
> terrestrial interference problems for the land cell users, in a large
> radius around the plane.
<snip>

Huh? Maximum output of most handheld cell phones is 0.6 watts with the old
in-car and bag phones going up to 3 watts. It can't output more than it's
maximum no matter how far you are away from the tower. The radius of
interference from 0.6 watt phones transmitting from inside an aluminum can
would be rather small. And it's a little hard to imagine a plane full of
people with bag phones.

>I also found a quote that went like this:
>"The restriction against cell phones is an FCC regulation and applies to
>all aircraft that can fly over a certain speed (maybe 200 kts?). Quickly
>switching cells during high speed flight causes all sorts of problems on
>the cell network."

The switching is done in a fraction of a second. The most that would happen
is a dropped call.

[Greg Copeland]

On Tue, 20 Apr 2004 16:35:03 -0500, FUji wrote:

>>Greg Copeland" > wrote in message
> ...
> <snip>
>> The general theory on modern cell phones in flight, goes like this:
>> The FCC also has a ban because when you're in flight, you're always at
>> least 6-8 miles away from the nearest cell tower. You end up communicating
>> with too many towers and bogging down the network. One or two such calls
>> is tolerable, but a whole plane load moving through would disrupt the
>> ground-based users of the network. Remember, the farther you are from a
>> tower, the more power your cell phone uses to communicate with it's tower;
>> up to 5-watts. Worse, a plane full of 5-watt transmitters causes
>> terrestrial interference problems for the land cell users, in a large
>> radius around the plane.
> <snip>
>
> Huh? Maximum output of most handheld cell phones is 0.6 watts with the old
> in-car and bag phones going up to 3 watts. It can't output more than it's
> maximum no matter how far you are away from the tower. The radius of
> interference from 0.6 watt phones transmitting from inside an aluminum can
> would be rather small. And it's a little hard to imagine a plane full of
> people with bag phones.
>

Hmm. Everything I've ever read says that maximum output is 5-watts. I'm
not saying that's right, but that has been a constant. I'm not sure how
far you could even transmit on 0.6 of watt.

>>I also found a quote that went like this:
>>"The restriction against cell phones is an FCC regulation and applies to
>>all aircraft that can fly over a certain speed (maybe 200 kts?). Quickly
>>switching cells during high speed flight causes all sorts of problems on
>>the cell network."
>
> The switching is done in a fraction of a second. The most that would happen
> is a dropped call.

People forget that cell switching is not magical. And it's certainly is
not zero cost. I must admit I do not fully understand everything that
goes on, but I am sure it's not as simple as you imply. Everytime a call
switches cells, it creates lots of work for the cell network to make sure
only a single tower handles that call. So, while it may take a fraction
of a second from a given phone and a given tower, there is lots going on
behind the scenes. Worse, instead of it going on with one, two or maybe
three towers, now it's causing a flurry of on twenty or more (highest
estimates I've read) towers. Let's also not forget that each tower can
only process and multiplex n-number of signals at a given time. DSPs,
just like your CPU, does have finite capacity. During cell switching, as
I understand it, this finite resource is being used on each tower in
contact with the phone. So, to say, "it causes all sorts of problems on
the cell network", does seem like a spot on statement to me.

[Greg Copeland]

On Tue, 20 Apr 2004 16:35:03 -0500, FUji wrote:

> Huh? Maximum output of most handheld cell phones is 0.6 watts with the old
> in-car and bag phones going up to 3 watts. It can't output more than it's
> maximum no matter how far you are away from the tower. The radius of
> interference from 0.6 watt phones transmitting from inside an aluminum can
> would be rather small. And it's a little hard to imagine a plane full of
> people with bag phones.

I thought I might just toss this out there. I quickly looked. I did not
have any trouble finding modern, handheld phones, with 2-watts output.
So, I think it's safe to say that we know for sure it's at least 2-watts.

[James Robinson]

Greg Copeland wrote:
>
> On Tue, 20 Apr 2004 16:35:03 -0500, FUji wrote:
>
> > Huh? Maximum output of most handheld cell phones is 0.6 watts with the old
> > in-car and bag phones going up to 3 watts. It can't output more than it's
> > maximum no matter how far you are away from the tower. The radius of
> > interference from 0.6 watt phones transmitting from inside an aluminum can
> > would be rather small. And it's a little hard to imagine a plane full of
> > people with bag phones.
>
> I thought I might just toss this out there. I quickly looked. I did not
> have any trouble finding modern, handheld phones, with 2-watts output.
> So, I think it's safe to say that we know for sure it's at least 2-watts.

Both of my run-of-the-mill Nokias have a maximum transmit power of 600
mW. They are two different digital/analog models.

[Peter Duniho]

"Greg Copeland" > wrote in message
...
> [...] I'm not sure how far you could even transmit on 0.6 of watt.

FRS (the 90's answer to walkie-talkies) is limited to 0.5 watts and is
considered usable up to about 2 miles (not counting obstructions). Range is
dependent not just on the transmitted power, but also how sensitive the
receiver is. Pitifully weak signals are received over distances of hundreds
of millions of miles on a regular basis (just ask NASA).

Pete

[Greg Copeland]

On Wed, 21 Apr 2004 00:53:13 +0000, James Robinson wrote:

> Greg Copeland wrote:
>>
>> On Tue, 20 Apr 2004 16:35:03 -0500, FUji wrote:
>>
>> > Huh? Maximum output of most handheld cell phones is 0.6 watts with the old
>> > in-car and bag phones going up to 3 watts. It can't output more than it's
>> > maximum no matter how far you are away from the tower. The radius of
>> > interference from 0.6 watt phones transmitting from inside an aluminum can
>> > would be rather small. And it's a little hard to imagine a plane full of
>> > people with bag phones.
>>
>> I thought I might just toss this out there. I quickly looked. I did not
>> have any trouble finding modern, handheld phones, with 2-watts output.
>> So, I think it's safe to say that we know for sure it's at least 2-watts.
>
> Both of my run-of-the-mill Nokias have a maximum transmit power of 600
> mW. They are two different digital/analog models.

Well, that's an interesting point. I know if I leave my phone on in the
air, it tends to degrade to analog mode (dual band phone). While I am
aware the digital mode uses far less power (just didn't realize that
little), perhaps the 5-watt maximum number is representative of phones
operating in analog mode? I dunno. That's my best guess.

[FUji]

"Greg Copeland" > wrote in message
...
> On Tue, 20 Apr 2004 16:35:03 -0500, FUji wrote:
>
> > Huh? Maximum output of most handheld cell phones is 0.6 watts with the
old
> > in-car and bag phones going up to 3 watts. It can't output more than
it's
> > maximum no matter how far you are away from the tower. The radius of
> > interference from 0.6 watt phones transmitting from inside an aluminum
can
> > would be rather small. And it's a little hard to imagine a plane full
of
> > people with bag phones.
>
> I thought I might just toss this out there. I quickly looked. I did not
> have any trouble finding modern, handheld phones, with 2-watts output.
> So, I think it's safe to say that we know for sure it's at least 2-watts.
>

0.7 watts is the maximum that is considered "safe" for handheld use by
medical experts. Any more than that gets your brain frying, so they say.
;-)

I've had cell phones for fifteen years (novatel, motorola, mitsubishi, etc.)
and all the handhelds except the ericssons were 0.6 watts. The ericssons
were only 0.5 watts! Way back then I remember if you complained about bad
reception with a handheld they'd tell you to "upgrade" to a transportable.

Any links or names of the ones you found?

[Greg Copeland]

On Tue, 20 Apr 2004 20:14:23 -0500, FUji wrote:

> "Greg Copeland" > wrote in message
> ...
>> On Tue, 20 Apr 2004 16:35:03 -0500, FUji wrote:
>>
>> > Huh? Maximum output of most handheld cell phones is 0.6 watts with the
> old
>> > in-car and bag phones going up to 3 watts. It can't output more than
> it's
>> > maximum no matter how far you are away from the tower. The radius of
>> > interference from 0.6 watt phones transmitting from inside an aluminum
> can
>> > would be rather small. And it's a little hard to imagine a plane full
> of
>> > people with bag phones.
>>
>> I thought I might just toss this out there. I quickly looked. I did not
>> have any trouble finding modern, handheld phones, with 2-watts output.
>> So, I think it's safe to say that we know for sure it's at least 2-watts.
>>
>
> 0.7 watts is the maximum that is considered "safe" for handheld use by
> medical experts. Any more than that gets your brain frying, so they say.
> ;-)
>
> I've had cell phones for fifteen years (novatel, motorola, mitsubishi, etc.)
> and all the handhelds except the ericssons were 0.6 watts. The ericssons
> were only 0.5 watts! Way back then I remember if you complained about bad
> reception with a handheld they'd tell you to "upgrade" to a transportable.
>
> Any links or names of the ones you found?

http://www.hazardousareadirect.com/Products/ECO-EX-HANDY04.htm
http://www.phonemerchants.com/poda3wadubac.html

All I did was a quick google and this was the first one that popped up.
It says, 2 watts, 1 watts, and 1 watts for it's maximum output for the
three supports networks. It is a tri-band phone.

The second link is a power amplifier which cranks output up to 3-watts.
Keep in mind, just bacause a phone may output less than maximum power,
doesn't have to mean they are not allowed to output higher. Perhaps we're
playing with semantics here. Perhaps the maximum allowed is 5-watts? And
most phones output less? I dunno. At any rate, right off the bat, I
didn't have any trouble finding a phone that has a maximum output of
2-watts.

[G.R. Patterson III]

FUji wrote:
>
> The switching is done in a fraction of a second. The most that would happen
> is a dropped call.

Not true. If you are a few thousand feet up, using one of the phones that uses the
old 800 MhZ bands, you will hit multiple cells which use the same radio frequency
set. The problem is not switching so much as it is interference with other calls. If
the ground equipment has the capability of detecting this interference (Motorola used
to do this), then you've blocked that frequency pair at every cell within range and
reduced their capacity by one call. If it can't detect and correct the problem, your
conversation may "step on" someone else's call.

If you are on the ground, you will only be able to reach one cell that uses the
frequency set you're using and there is no problem.

Now, if you have one of those "personal communication systems" (AKA "PCS phones"),
you will not have this problem in the air. These phones use frequency sets in the 900
MhZ range, use different technology, and are legal to use in the air. Of course,
non-professionals call them "cell phones", so you get all sorts of confusion there.
Some of them also use the old system for backup when they can't complete a call using
the PCS network, so you really have to check your manual.

This topic has been extensively discussed here for over 15 years that I know of. Back
when it mattered a lot more than it does now.

George Patterson
This marriage is off to a shaky start. The groom just asked the band to
play "Your cheatin' heart", and the bride just requested "Don't come home
a'drinkin' with lovin' on your mind".

[G.R. Patterson III]

Greg Copeland wrote:
>
> I thought I might just toss this out there. I quickly looked. I did not
> have any trouble finding modern, handheld phones, with 2-watts output.

They almost certainly are not cell phones. Probably PCS.

George Patterson
This marriage is off to a shaky start. The groom just asked the band to
play "Your cheatin' heart", and the bride just requested "Don't come home
a'drinkin' with lovin' on your mind".

[FUji]

"Greg Copeland" > wrote in message
...
> On Tue, 20 Apr 2004 16:35:03 -0500, FUji wrote:
> >
> > The switching is done in a fraction of a second. The most that would
happen
> > is a dropped call.
>
> People forget that cell switching is not magical. And it's certainly is
> not zero cost. I must admit I do not fully understand everything that
> goes on, but I am sure it's not as simple as you imply. Everytime a call
> switches cells, it creates lots of work for the cell network to make sure
> only a single tower handles that call. So, while it may take a fraction
> of a second from a given phone and a given tower, there is lots going on
> behind the scenes. Worse, instead of it going on with one, two or maybe
> three towers, now it's causing a flurry of on twenty or more (highest
> estimates I've read) towers. Let's also not forget that each tower can
> only process and multiplex n-number of signals at a given time. DSPs,
> just like your CPU, does have finite capacity. During cell switching, as
> I understand it, this finite resource is being used on each tower in
> contact with the phone. So, to say, "it causes all sorts of problems on
> the cell network", does seem like a spot on statement to me.
>

True. I oversimplified it. A dropped call is all the users would
experience.

Even though it is theoretically possible to overload the processing
capability, I doubt that it is really a significant problem in the real
world.

For example, a group of people standing at the top of the CN Tower using
their phones would be line-of-sight to almost every cell tower in the
Toronto area. The system would select the best tower and lock on.

A better example that includes moving: People on their phones driving
through downtown NYC. A densely populated area would need more towers with
closer spacing. With all the buildings acting as giant reflectors we now
have multipath signals from many towers as well as phones. If the system
can lock onto thousands of phones under these conditions, a couple of 747's
with about half of the people on phones would be minor.

As some pilots who used their phones in the air have reported, they have to
lower their altitude to get a signal. Regardless of what the reports say,
hitting twenty towers with such a low wattage is highly unlikely.

[Greg Copeland]

On Tue, 20 Apr 2004 20:59:28 -0500, FUji wrote:
>
> Even though it is theoretically possible to overload the processing
> capability, I doubt that it is really a significant problem in the real
> world.

It happens on the time. Capacity planning is part of their job. It's
just that proper planning by the various carriers tend to hide this fact.

>
> For example, a group of people standing at the top of the CN Tower using
> their phones would be line-of-sight to almost every cell tower in the
> Toronto area. The system would select the best tower and lock on.

Right, which means they are not changing towers and are only using the
resources of a single tower.

>
> A better example that includes moving: People on their phones driving
> through downtown NYC. A densely populated area would need more towers with
> closer spacing. With all the buildings acting as giant reflectors we now
> have multipath signals from many towers as well as phones. If the system
> can lock onto thousands of phones under these conditions, a couple of 747's
> with about half of the people on phones would be minor.

That's really part of a capacity planning issue, IMO. If you were to
figure out the average call density, it would probably be fairly sparse.
After all, only so many cars can fit in a given area. Now then, if you
have a plane with 250 people and half those are using their phone, that's
an extra 125 calls on each tower that is now suddenly passing from tower
to tower. That's a HUGE difference in capacity in a very short period of
time.

>
> As some pilots who used their phones in the air have reported, they have to
> lower their altitude to get a signal. Regardless of what the reports say,
> hitting twenty towers with such a low wattage is highly unlikely.

If it's reasonable to assume a ground based user can get two to three
towers at any given time, I don't think it's hard to easily imagine two,
three or even four times that since you're in the air with much fewer
obstructions (less scatter, direct, and father los), especially since
there is a much higher chance that your phone is operating at or near its
maximum output. Granted, chances are you not in a rural area if you're
hitting that many towers. But, just for the sake of argument, let's say
it's less. Is using use two or three times your normally alloted capacity
fair on the carriers? With enough phones in use at any given time, I can
easily imagine it playing heck with their capacity planning.

[Tim Baron]

x-no-archive: yes
"G.R. Patterson III" wrote:

>
> Now, if you have one of those "personal communication systems" (AKA "PCS phones"),
> you will not have this problem in the air. These phones use frequency sets in the 900
> MhZ range, use different technology, and are legal to use in the air.

Not 900 Mhz in the US. Perhaps you meant to say 1900 Mhz range.

[G.R. Patterson III]

Tim Baron wrote:
>
> Not 900 Mhz in the US. Perhaps you meant to say 1900 Mhz range.

You're correct, of course. The 900 MhZ band is for pagers and such.

George Patterson
This marriage is off to a shaky start. The groom just asked the band to
play "Your cheatin' heart", and the bride just requested "Don't come home
a'drinkin' with lovin' on your mind".

[G.R. Patterson III]

Greg Copeland wrote:
>
> The general theory on modern cell phones in flight, goes like this:
> The FCC also has a ban because when you're in flight, you're always at
> least 6-8 miles away from the nearest cell tower. You end up communicating
> with too many towers and bogging down the network.

No, you could be right beside the nearest tower. In general, any tower within about
20 miles of you will be able to receive you when you're on the ground (unless
something's blocking the signal). To eliminate conflict between calls, towers that
are neighbors use different frequency sets. When you make a call, the control system
polls all of the towers that can "hear" you and tells the closest one to accept the
call. That tower tells your phone what frequency pair to use. After that, only that
tower can "hear" your phone. If you move too far away, the control system will poll
all the towers again and have your phone switch frequencies.

Unfortunately, there aren't enough radio frequencies to allow every tower to use a
unique set, so there will probably be several towers between 30 and 60 miles from you
that use the same set of frequencies that your phone is using. They can't hear you
'cause they're too far away.

Now take off. As soon as you get 500' up, some of these towers can hear your phone.
If these towers are using the same frequency pair for other calls that your phone is
using, your call will bleed into those conversations. Some hardware systems can
detect conflicts like this and have other phones change frequencies. This hardware,
however, will log the ID of the phone that's causing the trouble, and you may get a
service termination notice.

The system designers carefully design the network to prevent call conflict due to
things like skyscrapers. Skyscrapers rarely move, however.

George Patterson
This marriage is off to a shaky start. The groom just asked the band to
play "Your cheatin' heart", and the bride just requested "Don't come home
a'drinkin' with lovin' on your mind".

[Elwood Dowd]

G.R. Patterson III wrote:
> <snip>
> Now, if you have one of those "personal communication systems" (AKA "PCS phones"),
> you will not have this problem in the air. These phones use frequency sets in the 900
> MhZ range, use different technology, and are legal to use in the air. Of course,

Are you sure PCS phones are legal in the air? As I understand it, this
is a hotly debated topic.

I'm in the process of turning my old cell phone back on. I have a
Qualcomm dual-mode phone that as I understand it is illegal to use in
the air. If a Sprint PCS phone is legal to use I would consider
changing phones. (Thought about an Iridium sat phone, but the $1.25/min
charges changed my mind!)

[Lisa]

Elwood Dowd wrote:

> G.R. Patterson III wrote:
> > <snip>
> > Now, if you have one of those "personal communication systems" (AKA "PCS phones"),
> > you will not have this problem in the air. These phones use frequency sets in the 900
> > MhZ range, use different technology, and are legal to use in the air. Of course,
>
> Are you sure PCS phones are legal in the air? As I understand it, this
> is a hotly debated topic.

There is no US FCC regulation against using PCS phones (which do not use the old 800 Mhz
band) in the air. There IS a US FCC regulation against using Part 22 devices in the air,
which would include 800 Mhz AMPS service (traditional analog cellular) as well as newer
digital services in this same band. Sprint and T-Mobile are examples of wireless carriers
which are strictly PCS. Some companies may use both the 800 band and something else. (And
GSM is now starting to be used in the 800 Mhz band in the US, not just in the US 1900 Mhz
band.)

However, the terms of service for each carrier may prohibit airborne operation.

[C J Campbell]

"Greg Copeland" > wrote in message
...
> Recentingly, in another thread, cell phones and planes came up. I
> thought others might be interested in these links.
>

I don't know about any FCC regulation as it relates to airspeed and I doubt
that any such regulation could be effectively enforced.

Cell phone jacks for headsets are a popular item. Actually using a cell
phone in an airplane is difficult. You get a lot of dropped calls. I
wouldn't want to try to fool with it while doing the flying. It is very
handy to report in if I am going to be late returning on a cross country.

No one has ever come up with any solid evidence that cellular phones
interfere with radios, blow up gas tanks, or do any of the other evil things
that cellular phones are supposed to do.

[Dylan Smith]

In article >, Greg Copeland wrote:
> Recentingly, in another thread, cell phones and planes came up. I
> thought others might be interested in these links.

Here is a first-hand cautionary tale on cell phones in flight.

It was a dark and stormy night (well, dark and rainy at least), and I
was flying with a friend back from Yorkshire to the IOM. It was my
friend's first "for real" ILS in the muck.

The flight was progressing well, and I was handling the radios, and
monitoring my friend's progress as we intercepted the localiser. It was
at that point we discovered his cell phone was still on and his wife was
calling. We found this out when through the audio we heard "Bp bb b b b
bp b b b bp b b bp brbrbrbrbrbrbbrbrbrbrbrbbrbrbrbrbrbrbrb!" at high
volume. If ATC called us at this point we wouldn't have heard. We
couldn't even hear each other over the intercom. I took over whilst he
got the thing turned off. Fortunately, it didn't intefere with the
localiser/glideslope.

Good job he wasn't solo or he'd have had to fly the ILS in a NORDO
condition, possibly not getting his landing clearance.

I think the inteference was picked up by the headset leads - his headset
lead went right over the pocket he had the phone in. (Also note we have
a different cell phone frequency here compared to the US, so US
cellphones might intefere with different things instead).

--
Dylan Smith, Castletown, Isle of Man
Flying: http://www.dylansmith.net
Frontier Elite Universe: http://www.alioth.net
"Maintain thine airspeed, lest the ground come up and smite thee"

[Elwood Dowd]

Thanks very much for a comprehensive answer! Not many of those are to
be found on usenet.

Lisa wrote:

> There is no US FCC regulation against using PCS phones (which do not use the old 800 Mhz
> band) in the air. There IS a US FCC regulation against using Part 22 devices in the air,
> which would include 800 Mhz AMPS service (traditional analog cellular) as well as newer
> digital services in this same band. Sprint and T-Mobile are examples of wireless carriers
> which are strictly PCS. Some companies may use both the 800 band and something else. (And
> GSM is now starting to be used in the 800 Mhz band in the US, not just in the US 1900 Mhz
> band.)
>
> However, the terms of service for each carrier may prohibit airborne operation.
>

[Greg Copeland]

On Wed, 21 Apr 2004 03:43:32 +0000, G.R. Patterson III wrote:

>
>
> Greg Copeland wrote:
>>
>> The general theory on modern cell phones in flight, goes like this:
>> The FCC also has a ban because when you're in flight, you're always at
>> least 6-8 miles away from the nearest cell tower. You end up communicating
>> with too many towers and bogging down the network.
>
> No, you could be right beside the nearest tower. In general, any tower within about
> 20 miles of you will be able to receive you when you're on the ground (unless
> something's blocking the signal). To eliminate conflict between calls, towers that
> are neighbors use different frequency sets. When you make a call, the control system
> polls all of the towers that can "hear" you and tells the closest one to accept the
> call. That tower tells your phone what frequency pair to use. After that, only that
> tower can "hear" your phone. If you move too far away, the control system will poll
> all the towers again and have your phone switch frequencies.

You exactly described what I less eloquently described elsewhere. What you described
qualifies as, "bogging down the network." It's not that you're "talking" on all these
towers. It's that you are using resources on all these towers at a very
high rate, as you move along, causing your call to jump from tower to
tower, in turn, causing the cycle to repeat over and over. Now, multiply
that with lots of other people using their phones on a plane, and I
think that clearly qualifies as, "You end up communicating with too many
towers and bogging down the network."


That's the complaint.

[Greg Copeland]

On Wed, 21 Apr 2004 01:45:25 +0000, G.R. Patterson III wrote:

>
>
> Greg Copeland wrote:
>>
>> I thought I might just toss this out there. I quickly looked. I did not
>> have any trouble finding modern, handheld phones, with 2-watts output.
>
> They almost certainly are not cell phones. Probably PCS.

I'm using layman's terminology, which would cover PCM, GSM, etc, etc, etc...

[Dylan Smith]

In article >, Tim Baron wrote:
> x-no-archive: yes
> "G.R. Patterson III" wrote:
>
>>
>> Now, if you have one of those "personal communication systems"
>(AKA "PCS phones"),

> Not 900 Mhz in the US. Perhaps you meant to say 1900 Mhz range.

What is PCS? Is it just marketdroid speak for GSM? (IIRC, the US uses
1900MHz for GSM)

--
Dylan Smith, Castletown, Isle of Man
Flying: http://www.dylansmith.net
Frontier Elite Universe: http://www.alioth.net
"Maintain thine airspeed, lest the ground come up and smite thee"

[Dylan Smith]

In article >, C J Campbell wrote:
> No one has ever come up with any solid evidence that cellular phones
> interfere with radios, blow up gas tanks, or do any of the other evil things
> that cellular phones are supposed to do.

I doubt they blow up gas tanks or the other evil things, but I have
first hand personal experience of a mobile phone intefering with either
the intercom or the COM radio of an aircraft (see earlier post in this
thread).

--
Dylan Smith, Castletown, Isle of Man
Flying: http://www.dylansmith.net
Frontier Elite Universe: http://www.alioth.net
"Maintain thine airspeed, lest the ground come up and smite thee"

[Peter]

Dylan Smith wrote:
> In article >, Tim Baron wrote:
>
>>x-no-archive: yes
>>"G.R. Patterson III" wrote:
>>
>>
>>>Now, if you have one of those "personal communication systems"
>>
>>(AKA "PCS phones"),
>
>
>>Not 900 Mhz in the US. Perhaps you meant to say 1900 Mhz range.
>
>
> What is PCS? Is it just marketdroid speak for GSM? (IIRC, the US uses
> 1900MHz for GSM)

No, it's just the term used to distinguish the newer 1900 MHz frequency
band from the older 800 MHz cellular band. The FCC auctioned off the
1900 MHz frequencies to allow more carriers to offer 'cellular-type'
services in each region and to make some money for the government.
GSM is one technology used by some of those carriers in this band, but
CDMA and TDMA technologies are also used.

[Ash Wyllie]

Jay Honeck opined

>> I think you have too much time on your hands...
>> cheers ... denny

>Actually, I think it's a cool topic.

>I'd be willing to fly slower than 200 knots if it meant I could legally use
>my cell phone in the air!

>:-)

Cirrus 1234A: XXX Center, Cirrus 34A would like to slow to 190.

XXX Center: Cirrus 34A, why?

Cirrus 1234A: I need to phone home.



-ash
Cthulhu for President!
Why vote for a lesser evil?

[James M. Knox]

Dylan Smith > wrote in
:
>
> I doubt they blow up gas tanks or the other evil things, but I have
> first hand personal experience of a mobile phone intefering with
> either the intercom or the COM radio of an aircraft (see earlier post
> in this thread).

The "Mythbusters" (see Discovery Channel, TV) tried. Never even got close
to blowing up a service station... well, not with the cell phone. <G>

That OWT started as a more "modern" version of the older two-way mobile
radios. [And I've known some hams that ran a California Kilowatt out of
their cars.] Demolition crews would put up big signs around the area they
were using explosives, saying "Please turn off all two-way radios."

The problem there was explosives, wired through thousands of feet back to
the detonator. Made a great antenna. <G>

So people just naturally assumed that if a 1000+ watt transmitter would do
it, than naturally so would a cell phone. <G>

-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------

[James M. Knox]

Elwood Dowd > wrote in
:

> Thanks very much for a comprehensive answer! Not many of those are to
> be found on usenet.

Unfortunately, the one "practical" thing that wasn't mentioned - although
the regs may allow the newer PCS and GSM types in the air, at altitude much
above around 2000 AGL they start not working. The design of the ground-
based cell-site antennas degrade the signals badly (even though the raw
signal strength may still show okay on your phone).

Multi-mode models may then try reverting to "cell" technology - but then
theoretically you are back in conflict with the FCC regs.

If someone can solve this "last mile" (or so) problem, with a solution that
doesn't require a LONG phone cord, there sure are a lot of interesting
things that could then be done in our cockpits.

-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------

[Kyler Laird]

Greg Copeland > writes:

>> They almost certainly are not cell phones. Probably PCS.

>I'm using layman's terminology, which would cover PCM, GSM, etc, etc, etc...

Oh, surely not! NOBODY (except me) calls those "cell phones".
http://groups.google.com/groups?hl=en&safe=off&rnum=4&selm=356A947C.68B0%40earthlink.net

Good thing we still have George around to explain this to us. I think we've
lost the brilliant educator Jerry Bransford.
http://groups.google.com/groups?selm=3500183A.3058%40cts.com&output=gplain

--kyler

[David Brooks]

I'm tryint to speed-read all this excellent information, and I still don't
think I have an answer to my question:

By leaving my phone switched on, but *not making an outgoing call*, am I
doing no harm, or negligible harm, to the system?

Assume also that nobody calls me.

-- David Brooks

"G.R. Patterson III" > wrote in message
...
>
>
> Greg Copeland wrote:
> >
> > The general theory on modern cell phones in flight, goes like this:
> > The FCC also has a ban because when you're in flight, you're always at
> > least 6-8 miles away from the nearest cell tower. You end up
communicating
> > with too many towers and bogging down the network.
>
> No, you could be right beside the nearest tower. In general, any tower
within about
> 20 miles of you will be able to receive you when you're on the ground
(unless
> something's blocking the signal). To eliminate conflict between calls,
towers that
> are neighbors use different frequency sets. When you make a call, the
control system
> polls all of the towers that can "hear" you and tells the closest one to
accept the
> call. That tower tells your phone what frequency pair to use. After that,
only that
> tower can "hear" your phone. If you move too far away, the control system
will poll
> all the towers again and have your phone switch frequencies.
>
> Unfortunately, there aren't enough radio frequencies to allow every tower
to use a
> unique set, so there will probably be several towers between 30 and 60
miles from you
> that use the same set of frequencies that your phone is using. They can't
hear you
> 'cause they're too far away.
>
> Now take off. As soon as you get 500' up, some of these towers can hear
your phone.
> If these towers are using the same frequency pair for other calls that
your phone is
> using, your call will bleed into those conversations. Some hardware
systems can
> detect conflicts like this and have other phones change frequencies. This
hardware,
> however, will log the ID of the phone that's causing the trouble, and you
may get a
> service termination notice.
>
> The system designers carefully design the network to prevent call conflict
due to
> things like skyscrapers. Skyscrapers rarely move, however.
>
> George Patterson
> This marriage is off to a shaky start. The groom just asked the band
to
> play "Your cheatin' heart", and the bride just requested "Don't come
home
> a'drinkin' with lovin' on your mind".

[C J Campbell]

"David Brooks" > wrote in message
...
> I'm tryint to speed-read all this excellent information, and I still don't
> think I have an answer to my question:
>
> By leaving my phone switched on, but *not making an outgoing call*, am I
> doing no harm, or negligible harm, to the system?
>
> Assume also that nobody calls me.
>

Probably not. Digital phones have unique identifiers and are actually
supposed to be picked up by more than one tower at a time. If too many
towers pick up the phone then they electronically assign that phone to just
one tower and the others reject it. Since it is a digital stream, each
frequency can handle many cellular phones. It would be very difficult to bog
down the system with digital phones.

The problem is that the digital signals tend to be too weak, so the phone
frequently switches to analog when you start using it in an airplane. At the
very least, your phone will keep switching from one tower to another,
constantly searching even when you are not talking on it, and that will run
down the battery.

I recall reading somewhere that FCC regulations against using cellular
phones in flight do not apply to digital phones.

[C J Campbell]

"C J Campbell" > wrote in message
...
>
> I recall reading somewhere that FCC regulations against using cellular
> phones in flight do not apply to digital phones.
>
>

Nevertheless, I don't find any exception in this part:


§ 22.925 Prohibition on airborne operation of cellular telephones.
Cellular telephones installed in or carried aboard airplanes, balloons or
any other type of aircraft must not be operated while such aircraft are
airborne (not touching the ground). When any aircraft leaves the ground, all
cellular telephones on board that aircraft must be turned off. The following
notice must be posted on or near each cellular telephone installed in any
aircraft:

“The use of cellular telephones while this aircraft is airborne is
prohibited by FCC rules, and the violation of this rule could result in
suspension of service and/or a fine. The use of cellular telephones while
this aircraft is on the ground is subject to FAA regulations.”

[C J Campbell]

"C J Campbell" > wrote in message
...
>
> "C J Campbell" > wrote in message
> ...
> >
> > I recall reading somewhere that FCC regulations against using cellular
> > phones in flight do not apply to digital phones.
> >
> >
>
> Nevertheless, I don't find any exception in this part:
>
>
> § 22.925 Prohibition on airborne operation of cellular telephones.
> Cellular telephones installed in or carried aboard airplanes, balloons or
> any other type of aircraft must not be operated while such aircraft are
> airborne (not touching the ground). When any aircraft leaves the ground,
all
> cellular telephones on board that aircraft must be turned off. The
following
> notice must be posted on or near each cellular telephone installed in any
> aircraft:
>
> “The use of cellular telephones while this aircraft is airborne is
> prohibited by FCC rules, and the violation of this rule could result in
> suspension of service and/or a fine. The use of cellular telephones while
> this aircraft is on the ground is subject to FAA regulations.”

Of course, PCS phones are operated under Part 24 of the FCC regulations,
which have no prohibition against use in aircraft.

[Greg Copeland]

On Wed, 21 Apr 2004 08:10:57 -0700, David Brooks wrote:

> I'm tryint to speed-read all this excellent information, and I still don't
> think I have an answer to my question:
>
> By leaving my phone switched on, but *not making an outgoing call*, am I
> doing no harm, or negligible harm, to the system?
>
> Assume also that nobody calls me.
>

It's probably safe to say that it is disturbing the the network, even if
you are not actually on a call. Having said that, in a slower GA plane
(130kts or less; number pulled from my tail pipe), in a rural area, the
impact *probably* is minimal. Especially considering the more rural you
are, the less the capacity demands on the towers, from other users in the
area, are likely to be.

On the other hand, imagine a commercial plane full of people and
the majority of them have a cell phones on. I think we've pretty well
established that it can very disturbing to the networks and their capacity.

[Don Tuite]

On Wed, 21 Apr 2004 08:59:34 -0700, "C J Campbell"
> wrote:

>
>"C J Campbell" > wrote in message
...
>>
>> I recall reading somewhere that FCC regulations against using cellular
>> phones in flight do not apply to digital phones.
>>
>>
>
>Nevertheless, I don't find any exception in this part:
>
>
>§ 22.925 Prohibition on airborne operation of cellular telephones.
>Cellular telephones installed in or carried aboard airplanes, balloons or
>any other type of aircraft must not be operated while such aircraft are
>airborne (not touching the ground). When any aircraft leaves the ground, all
>cellular telephones on board that aircraft must be turned off. The following
>notice must be posted on or near each cellular telephone installed in any
>aircraft:
>
>“The use of cellular telephones while this aircraft is airborne is
>prohibited by FCC rules, and the violation of this rule could result in
>suspension of service and/or a fine. The use of cellular telephones while
>this aircraft is on the ground is subject to FAA regulations.”

Here's the FCC site on cellular telephones:

http://wireless.fcc.gov/services/cellular/

Here's the FCC site on PCS telephones:

http://wireless.fcc.gov/services/broadbandpcs/

The prohibition is in the first (Part 22). There is no corresponding
prohibition in the second (Part 24).

Don

[Elwood Dowd]

Okay... so it is now well established that 800MHz operation is illegal
in aircraft, and while 1900MHz operation is not prohibited by laws, the
reality is that it doesn't work that well over 2000AGL, more or less.

Now the real question---as a backup phone for traveling, does it make
more sense to go with a "cheapie" PCS-only phone, or pay more for
Verizon and a tri-mode phone, assuming that all modes are either illegal
or impractical in the air?

I have learned much from this discussion and in researching earlier ones!

[Teacherjh]

>>
--
(for Email, make the obvious changes in my address)

[Teacherjh]

>>
as a backup phone for traveling, does it make
more sense to go with a "cheapie" PCS-only phone, or pay more for
Verizon and a tri-mode phone, assuming that all modes are either illegal
or impractical in the air?
<<

(oops)

Depends what kind of "backup" you are looking for. I use my palm VIIx and CBAV
for aviation stuff, and a full tri-mode cell phone for cell phone stuff. I
don't have a backup comm, but in an emergency I would certainly use the cell.
If I were looking for something specifically for an aviation emergency backup,
I'd get a portable nav-comm.

Jose

--
(for Email, make the obvious changes in my address)

[G.R. Patterson III]

C J Campbell wrote:
>
> I recall reading somewhere that FCC regulations against using cellular
> phones in flight do not apply to digital phones.

No, the regulations differential between PCS and cellular. Digital cellular phones
still create problmes.

George Patterson
This marriage is off to a shaky start. The groom just asked the band to
play "Your cheatin' heart", and the bride just requested "Don't come home
a'drinkin' with lovin' on your mind".

[Teacherjh]

>>
No, the regulations differential between PCS and cellular. Digital cellular
phones
still create problmes.
<<

What's the difference between PCS and digital cellular?

Jos

--
(for Email, make the obvious changes in my address)

[Newps]

"Greg Copeland" > wrote in message
...


> Hmm. Everything I've ever read says that maximum output is 5-watts. I'm
> not saying that's right, but that has been a constant.

At 5 watts your battery would last about 5 minutes, if that.

I'm not sure how
> far you could even transmit on 0.6 of watt.

With my external antenna that I use when hunting I usually see 25-30 miles
without much problem.

[G.R. Patterson III]

Teacherjh wrote:
>
> What's the difference between PCS and digital cellular?

The main thing is the frequency set. By definition, cellphones use frequencies near
the middle of the 800 MhZ band. By definition, PCS phones are up in the 1900 MhZ
band.

George Patterson
This marriage is off to a shaky start. The groom just asked the band to
play "Your cheatin' heart", and the bride just requested "Don't come home
a'drinkin' with lovin' on your mind".

[Dylan Smith]

In article >, Newps wrote:
>
> "Greg Copeland" > wrote in message
> ...
>
>
>> Hmm. Everything I've ever read says that maximum output is 5-watts. I'm
>> not saying that's right, but that has been a constant.
>
> At 5 watts your battery would last about 5 minutes, if that.

My Nokia 6820 will give 7 hours talk time and 10 days just switched on
off a tiny battery. There's no way it's even 1 watt transmit, let alone
5 (at least under normal circumstances).

--
Dylan Smith, Castletown, Isle of Man
Flying: http://www.dylansmith.net
Frontier Elite Universe: http://www.alioth.net
"Maintain thine airspeed, lest the ground come up and smite thee"

[Mark]

Greg Copeland > wrote in message >...
> Recentingly, in another thread, cell phones and planes came up. I
> thought others might be interested in these links.
>
> http://www.eweek.com/article2/0,1759,1568024,00.asp
> http://wirelesscabin.com/
> http://www.wired.com/wired/archive/12.04/start.html?pg=12
>
> The general theory on modern cell phones in flight, goes like this:
> The FCC also has a ban because when you're in flight, you're always at
> least 6-8 miles away from the nearest cell tower. You end up communicating
> with too many towers and bogging down the network. One or two such calls
> is tolerable, but a whole plane load moving through would disrupt the
> ground-based users of the network. Remember, the farther you are from a
> tower, the more power your cell phone uses to communicate with it's tower;
> up to 5-watts. Worse, a plane full of 5-watt transmitters causes
> terrestrial interference problems for the land cell users, in a large
> radius around the plane.
><snip>

Back in the mid 90's I was flying to Boston from Kentucky to do aerial
photography. The company I worked for provided us with the cell
phones. On this trip I was using one of the old bag phones (I think
they put ot 3 watts?). Anyway, We were flying in a C-310 around
Ashland Ky (about 5000 feet) and we made a phone call and talked for
less than 5 minutes. Well, about 25 minutes later we made another
call, I think we were just South of Pittsburg (??). So, jump forward
to the next day. We were in Boston and were going to start a long day
of photography. We needed to call back to our boss in KY and the
phone did not work. I ended up calling the cell phone company from a
land line.

They told me that on the previous day my cell phone made a call on a
cell tower near Ashland Ky. About 25 minutes later a cell call was
placed from Pittsburg, PA. They cell company flagged this call since
they believed that NO one could travel from Ashland Ky to Pittsburg in
20-25 minutes. They believed that the cell phone ID was cloned. I
told them we were on a very important business trip and to turn back
on the phone and we would take care of the problem later. I didn't
tell them we were flying and placing the calls. ;-)

Recently I upgraded by 2 year old Cingular phone to the new GSM phone
(Motorola V400). I went flying and noticed that every few minutes I
would get a funny buzzing sounds on my Telex ANR headsets. My friend
was using traditional Non-ANR David Clarke headsets and didn't hear
any buzz. I've also noticed that if I place this GSM phone near my
computer monitor or speakers at work it would produce the same buzz.
I guess these new GSM phones will cause some strange reactions on
aviation (and ANR) frequences.

[Dima Volodin]

"Mark" > wrote in message
om...

> Recently I upgraded by 2 year old Cingular phone to the new GSM phone
> (Motorola V400). I went flying and noticed that every few minutes I
> would get a funny buzzing sounds on my Telex ANR headsets. My friend
> was using traditional Non-ANR David Clarke headsets and didn't hear
> any buzz. I've also noticed that if I place this GSM phone near my
> computer monitor or speakers at work it would produce the same buzz.
> I guess these new GSM phones will cause some strange reactions on
> aviation (and ANR) frequences.

It's sort of a feature of GSM (no matter what frequency band) and iDEN phones to
announce themselves on whatever electronics is nearby. Folks in Europe are
pretty accustomed to hear an incoming call on their TV sets even before the
phone rings. When I used to carry my company NEXTEL phone with me, I could hear
it changing cells on my AR108 airband scanner. The moral is - try _not_ to use
TDMA-based (DAMPS, GSM, and iDEN) phones while airborne.


Dima

[Paul Sengupta]

"Greg Copeland" > wrote in message
...
> On Tue, 20 Apr 2004 16:35:03 -0500, FUji wrote:
>
> > Huh? Maximum output of most handheld cell phones is 0.6 watts with the
old
> > in-car and bag phones going up to 3 watts.
> > The radius of
> > interference from 0.6 watt phones transmitting from inside an aluminum
can
> > would be rather small.

> I'm not sure how far you could even transmit on 0.6 of watt.

From London, on the 144MHz band, under the right conditions, I
once talked to a guy in Germany through a repeater in Belgium on
my 1W handheld. I then switched down to 150mW and could still
talk to him clearly. This was from the 12th floor of a building.

It's amazing how far 0.6W will go from a plane...if not for a good
quality phone call, at least to cause some interference.

> People forget that cell switching is not magical. And it's certainly is
> not zero cost. I must admit I do not fully understand everything that
> goes on, but I am sure it's not as simple as you imply. Everytime a call
> switches cells, it creates lots of work for the cell network to make sure
> only a single tower handles that call. So, while it may take a fraction
> of a second from a given phone and a given tower, there is lots going on
> behind the scenes. Worse, instead of it going on with one, two or maybe
> three towers, now it's causing a flurry of on twenty or more (highest
> estimates I've read) towers. Let's also not forget that each tower can
> only process and multiplex n-number of signals at a given time. DSPs,
> just like your CPU, does have finite capacity. During cell switching, as
> I understand it, this finite resource is being used on each tower in
> contact with the phone. So, to say, "it causes all sorts of problems on
> the cell network", does seem like a spot on statement to me.

Not only does it cause these problems with signalling in the network,
it also causes interference in other ways. With analogue, it will render
the frequency used unusable for the same frequency, repeated through
the 7 or 21 cell re-use pattern over the transmitted area. With TDMA
(D-AMPS or GSM), you'd wipe out that time slot on that frequency.
Greater than about 20 miles away, the time delay on the transmitted
signal would mean you'd also wipe out the adjacent time slot. You could
be decreasing capacity significantly over a wide area.

With CDMA I'm not sure about the interference potential, though it's
bound to increase the noise. I took our test gear up in the plane over
Newbury one day to see what I could receive. I got well over 20
cells and it was adding, deleting and replacing radio links like mad.
Absolute chaos on the network. Note that this network had not yet
been launched to the public (Vodafone UMTS - 3G).

It's not so much the "tower"s processing capacity, but that of the
BSC/MSC (or RNC on CDMA) controlling the base stations, and
also the capacity of the signalling links. All this is finite.

Someone said something (I've heard it said a few times) that the phone
"locks on" to the nearest cell. In laymans terms, yes. In actual terms,
you're transmitting, just like any other transmitter. The cell used for
communication will be the one receiving you the strongest. Note that
the neighbouring cells will be on different frequencies, so your phone
will tune to one of the frequencies used by the strongest cell. There is
then a re-use pattern, and the same frequencies will be re-used somewhere
a certain distance away, depending on the cell size. The cell size depends
on whether you're in an urban or rural environment...in an urban
environment they use a smaller cell size - lower power, more obstructions,
so the next cell using the same frequencies will be closer. They're banking
on the other cells not being able to pick you up due to your low power
and the buildings, hills,. trees and so on blocking the signal. (note that
the frequency thing doesn't apply to CDMA)

If conditions are right (wrong?) you may be picked up by other cells
on the same frequency...this is interference. If this is above a certain
level, this same frequency on the other cell will be rendered unusable.
(or that time slot on that frequency...and maybe the adjacent one, as
mentioned above).

If you use a phone in the air over an urban environment, you will cause
a large amount of interference. If you're down low over a rural area,
you may not cause any at all.

Paul

[gatt]

"Ash Wyllie" > wrote in message
...


> Cirrus 1234A: I need to phone home.

"SHUT UP AND FLY!!!" :>

My instrument instructor is also a real estate agent. Her cell phone rang
during runup yesterday and she confirmed a closed sale, but not without
difficulty.

-c

[G.R. Patterson III]

gatt wrote:
>
> My instrument instructor is also a real estate agent. Her cell phone rang
> during runup yesterday and she confirmed a closed sale, but not without
> difficulty.

My wife forwarded me an Andy Cap cartoon yesterday. Some dude is chatting on the
phone at the pub trying to set up a business deal. He asks Andy if he has the time.
Andy says "Yes, it's exactly two minutes before that phone goes through the window."
Love it.

George Patterson
None of us is as dumb as all of us.