AM radio reception inside passenger planes?

[Ether Hopper]

No one has mentioned that in many cases you need the pilot's permission to
operate a radio or other electronic device for that matter on a commercial
airliner. That includes AM/FM radios.

Radio emissions may screw up the plane's avionics.

See URL:
http://www.fordyce.org/scanning/scanning_info/scan_fly.html

It sez:
"The FAA does not allow inflight use of walkie-talkies, radio controlled
toys, AM/FM radios, portable telephones, or portable television sets, all of
which may affect aircraft radio and navigation equipment"

Also cruise ships may deny use of two way (FRS) or ham radios -- always
check with the communications officer.

For Hams always check with the person in charge on any commercial
transportation, busses, taxi's, ships planes etc.

Yeah yeah I know you did it without getting permission, but read the URL as
to what airlines have published.

And I know from personal experience that some cruise lines do not allow FRS
or ham radios transmissions.

--
RF Gotta Go SomeWhere



"nick smith" <NickS@ntlworld.com> wrote in message
news:MZHud.680$Uh.421@newsfe1-win.ntli.net...

"Geoff Glave" <nospam@nospam.com> wrote in message
news:HxHud.9448$eb3.8331@clgrps13...
Any explanation for this?

FM radio generally operates at longer range than AM radio, however it's
limited to line-of-sight. However, when you're 40,000 feet up you can
"see"
a lot of transmitters hence the FM signals.

Cheers,
Geoff Glave
Vancouver, Canada



I reckon you just answered the wrong question !!

The reason A.M. radio can not be received in a plane is that it is a
Faraday
cage to the (lower frequency) A.M
frequencies, whereas the VHF frequencies can just about get through the
windows.

There may be a bit of frequency / range issue as well but top band and 80
mtrs
gets across the pond so
I don't think this is the issue here...

Nick

 

[Dave Bushong]

Some Guy wrote:

I have no trouble receiving FM radio broadcasts on a small am/fm radio
I sometimes listen to while onboard commercial jet airliners (flying
at cruise altitude), but I never seem to be able to pick up AM radio
stations. It's just static across the AM band.

Any explanation for this?

Yes, there is. The AM cops have figured you out, since what you are
doing is illegal on commercial airliners. The FM cops are a little
slower, but they will pull the plug on you also, eventually.

Seriously, though, you are inside a metal cigar tube you call an
airplane, and you are being shielded by the body of the aircraft.
Although windows (portholes, not Gates), and the metal itself, don't
block out signals completely, you will see an effect from this (look up
"Faraday Cage" on google). AM broadcast is a very long wavelength
(hundreds of meters long) whereas FM broadcast is a smaller wavelength
(around 3 meters). If you were trying to throw a bunch of marbles
through an upstairs window, you would probably be able to do it. But if
you were trying to throw a bunch of beachballs through an upstairs
window, it wouldn't be as easy, right?

The aperture is the important issue. Although the airplane is not a
completely shielded RF-proof "screen room", it acts somewhat like one.
That is why avionics antennas are on the outside of the plane, not
inside. That is also why there is a teeny mesh grid in the door of your
microwave oven - they have to be that small to block the microwaves.

Using my example before: if you are throwing beachballs (AM broadcast),
or marbles (FM broadcast) or a handful of sand (microwaves), how small
would you want the window to be in order to block it?

OK, getting back to my first paragraph, if you are ever on a plane with
me, please let me know, so I can take the next flight. The local
oscillator of FM receivers is often on the same frequency as the VOR
stations that airplanes use to naviagate with, and can cause
interference. There are failsafe solutions that the pilot has, to deal
with loss of VOR coverage, but I don't want to depend on them because
you are listening to gangster rap at 32,000 feet. Get an iPod or something.

All the best,
Dave

 

[Ed Price]

"Ian Jackson" <IanJacksonRemoveThisBit@g3ohx.demon.co.uk> wrote in message
news:qQ5qidE8P1uBFw7f@g3ohx.demon.co.uk...

In message <piIud.4676$ve.1869@fed1read06>, Ether Hopper <EH@skip.net
writes
No one has mentioned that in many cases you need the pilot's permission to
operate a radio or other electronic device for that matter on a commercial
airliner. That includes AM/FM radios.

Radio emissions may screw up the plane's avionics.

Virgin included the use of radio receivers in their 'permitted list' about
3 years ago. However, I do wonder about the use of the FM broadcast band
because the LO (tuned freq + 10.7MHz) can land up right on top of
something important in the ATC band.
Ian.
--

Exactly the concern. LO's are used for superhet receivers, and fancier
receivers are more computer than analog RF. So now, you have a clock
oscillator, with it's harmonics, as another RF source. And don't tell me
these emissions are negligible. Receiver (and other electronics
manufacturers) sweat blood to reduce those emissions so that they can meet
FCC Part 15 (among other) requirements (modest radiation limits at 3 meters
distance from the test specimen).

The fact that apertures in the fuselage allow FM frequencies INTO the
aircraft, letting you pick them up with the miserably small FM antenna in
your receiver, also means that LO leakage from your receiver can get OUT of
those same apertures.

You now have the effect of having a small radiation source immediately
outside the fuselage, just feet or so from the Avionics antennas. What are
the coupling effects? What frequency will your LO land on? Do you feel
lucky, punk?

So, in all honesty, YOU can't really say how dangerous operation of an FM
receiver will be; but you KNOW that it's potentially harmful.

The advice to ask the PIC (pilot in command) to make allowance for you is
just plain dumb. The guy is an aircraft driver, not an expert in RF
propagation. He has overall responsibility for getting you to your
destination while avoiding legal exposure to himself and the airline. You
are asking him to allow a potentially dangerous device to be operated just
for your convenience and entertainment. Switch roles for just a minute.
Would YOU allow that? Now switch back. If your PIC would allow it, what else
would he be willing to allow or overlook?

While I will admit that aircraft disasters are rarely caused by a single
factor, it's just plain dumb to add risks that you don't need to take. I
want pilots who are conservative, who do a thorough pre-flight walk-around
even when it's raining, and who will enforce rational rules on
self-centered, ignorant passengers. Can't you put your electronic life on
hold for a few hours? Whatever happened to reading a book, or just looking
out the window?

Ed
wb6wsn

 

[Ether Hopper]

Part 91 GENERAL OPERATING AND FLIGHT RULES
Subpart A--General


FAA Regulations Sec. 91.21

Portable electronic devices.

(a) Except as provided in paragraph (b) of this section, no person may
operate, nor may any operator or pilot in command of an aircraft allow the
operation of, any portable electronic device on any of the following
U.S.-registered civil aircraft:
(1) Aircraft operated by a holder of an air carrier operating certificate or
an operating certificate; or
(2) Any other aircraft while it is operated under IFR.
(b) Paragraph (a) of this section does not apply to--
(1) Portable voice recorders;
(2) Hearing aids;
(3) Heart pacemakers;
(4) Electric shavers; or
(5) Any other portable electronic device that the operator of the aircraft
has determined will not cause interference with the navigation or
communication system of the aircraft on which it is to be used.
(c) In the case of an aircraft operated by a holder of an air carrier
operating certificate or an operating certificate, the determination
required by paragraph (b)(5) of this section shall be made by that operator
of the aircraft on which the particular device is to be used. In the case of
other
aircraft, the determination may be made by the pilot in command or other
operator of the aircraft.
------------------------------------

Seems to me the pilot ought to know.

Again I direct you to URL:
http://www.fordyce.org/scanning/scanning_info/scan_fly.html

--
RF Gotta Go SomeWhere



"Ed Price" <edprice@cox.net> wrote in message
news:ymKud.23648$Af.3577@fed1read07...

"Ian Jackson" <IanJacksonRemoveThisBit@g3ohx.demon.co.uk> wrote in message
news:qQ5qidE8P1uBFw7f@g3ohx.demon.co.uk...
In message <piIud.4676$ve.1869@fed1read06>, Ether Hopper <EH@skip.net
writes
No one has mentioned that in many cases you need the pilot's permission
to
operate a radio or other electronic device for that matter on a
commercial
airliner. That includes AM/FM radios.

Radio emissions may screw up the plane's avionics.

Virgin included the use of radio receivers in their 'permitted list'
about 3 years ago. However, I do wonder about the use of the FM broadcast
band because the LO (tuned freq + 10.7MHz) can land up right on top of
something important in the ATC band.
Ian.
--


Exactly the concern. LO's are used for superhet receivers, and fancier
receivers are more computer than analog RF. So now, you have a clock
oscillator, with it's harmonics, as another RF source. And don't tell me
these emissions are negligible. Receiver (and other electronics
manufacturers) sweat blood to reduce those emissions so that they can meet
FCC Part 15 (among other) requirements (modest radiation limits at 3
meters distance from the test specimen).

The fact that apertures in the fuselage allow FM frequencies INTO the
aircraft, letting you pick them up with the miserably small FM antenna in
your receiver, also means that LO leakage from your receiver can get OUT
of those same apertures.

You now have the effect of having a small radiation source immediately
outside the fuselage, just feet or so from the Avionics antennas. What are
the coupling effects? What frequency will your LO land on? Do you feel
lucky, punk?

So, in all honesty, YOU can't really say how dangerous operation of an FM
receiver will be; but you KNOW that it's potentially harmful.

The advice to ask the PIC (pilot in command) to make allowance for you is
just plain dumb. The guy is an aircraft driver, not an expert in RF
propagation. He has overall responsibility for getting you to your
destination while avoiding legal exposure to himself and the airline. You
are asking him to allow a potentially dangerous device to be operated just
for your convenience and entertainment. Switch roles for just a minute.
Would YOU allow that? Now switch back. If your PIC would allow it, what
else would he be willing to allow or overlook?

While I will admit that aircraft disasters are rarely caused by a single
factor, it's just plain dumb to add risks that you don't need to take. I
want pilots who are conservative, who do a thorough pre-flight walk-around
even when it's raining, and who will enforce rational rules on
self-centered, ignorant passengers. Can't you put your electronic life on
hold for a few hours? Whatever happened to reading a book, or just looking
out the window?

Ed
wb6wsn

 

[Richard Clark]

On Sat, 11 Dec 2004 14:11:44 -0800, "Ed Price" <edprice@cox.net>
wrote:

You
are asking him to allow a potentially dangerous device to be operated just
for your convenience and entertainment. Switch roles for just a minute.

Hi Ed,

This would make sense (to switch roles) if the administration hadn't
trumped that call. Reports recently indicate that the FAA may soon
allow anyone, anytime, to make cell phone calls while in flight.

Anything goes for a price. The FDA has proven that it is no longer
the watchdog of medicine, and the FCC is the gateway for spectrum
bargains and marketplace sweeps.

With these acronyms, one may well wonder what the "F" stands for.

73's
Richard Clark, KB7QHC

 

[Some Guy]

What a load of horse shit.

You guys are acting as if the engines and flight control surfaces of
an aircraft are intimately tied to the plane's radio receiver, and the
slightest odd or out-of-place signal that it receives is enough to
send any plane into a tail spin.

All this while the air travel industry is considering allowing
passengers to use their own cell phones WHILE THE PLANES ARE IN FLIGHT
by adding cell-phone relay stations to the planes and allowing any
such calls to be completed via satellite. So I guess the feeble
radiation by my FM radio (powered by 2 AAA batteries) is enough to
cause a plane to dive into the ocean, but the guy next to me putting
out 3 watts of near-microwave energy is totally safe.

What about my hand-held GPS unit? Any chance me using it (during all
phases of a flight, which I do routinely) will result in a one-way
ticket to kingdom come?

Getting back to the original question (poor to non-existant AM
reception), I understand the idea of aperature and long wavelenths of
AM radio and the size of airplane windows - but what about the effect
of ALL the windows on a plane? Don't they create a much larger
effective apperature when you consider all of them? And since the
plane isin't grounded, isin't the exterior shell of a plane
essentially transparent to all RF (ie it's just a re-radiator) because
it's not at ground potential?

 

[Richard Clark]

On Sat, 11 Dec 2004 19:10:18 -0500, Some Guy <Some@guy.com> wrote:

Getting back to the original question (poor to non-existant AM
reception), I understand the idea of aperature and long wavelenths of
AM radio and the size of airplane windows - but what about the effect
of ALL the windows on a plane? Don't they create a much larger
effective apperature when you consider all of them?

This becomes a matter of the distance between them and the phase
separation at any wavelength. What you describe is a common technique
for coupling power between waveguides (in what are called directional
couplers). However, this is not the same thing as accumulating and
enlarging an opening because such couplers will add energy in one
direction, and subtract it in the other (which makes for their
directionality).

And since the
plane isin't grounded, isin't the exterior shell of a plane
essentially transparent to all RF (ie it's just a re-radiator) because
it's not at ground potential?

Ground does not always mean "at one with the dirt and rocks." At one
time it did, when cowboys put up talking wires, and indians pulled
them down. Ground has since come to mean "common" (which when you
think of it, brings us back to dirt, metaphorically). Common means
that everything is at the same potential. If there is no potential
difference, then there is no way to measure a voltage based signal.
In other words, it's a massive short circuit, and the only way to
sense a signal is to inductively couple to the short circuit current.

This takes us to the second killer courtesy of physics. High
frequency current travels on the surface of smallest, positive radius.
AM frequency qualifies here in spades, even though it is
conventionally called not HF but MF (even VLF qualifies as High
Frequency in this context). The aircraft frame thus presents both
curvature and radius such that the current confines itself to the
outside of the shell with an inclination for the narrow wings and tail
section, rather than the elongated body.

You might be tempted to inductively tap into this frame current, but
then you are on the negative, inside radius of the current carrier
(makes the tube interior self-shielding). Whatever current is
flowing, is on the outside of the skin, not the inside - that is,
until we consider skin depth and penetration. But then it appears
that experience described here suggests that not much of that frame
current penetrates inside.

73's
Richard Clark, KB7QHC

 

[Roy Lewallen]

Some Guy wrote:

What a load of horse shit.

You guys are acting as if the engines and flight control surfaces of
an aircraft are intimately tied to the plane's radio receiver, and the
slightest odd or out-of-place signal that it receives is enough to
send any plane into a tail spin.

All this while the air travel industry is considering allowing
passengers to use their own cell phones WHILE THE PLANES ARE IN FLIGHT
by adding cell-phone relay stations to the planes and allowing any
such calls to be completed via satellite. So I guess the feeble
radiation by my FM radio (powered by 2 AAA batteries) is enough to
cause a plane to dive into the ocean, but the guy next to me putting
out 3 watts of near-microwave energy is totally safe.

What about my hand-held GPS unit? Any chance me using it (during all
phases of a flight, which I do routinely) will result in a one-way
ticket to kingdom come?

Too bad it's not that simple. But if you're really into this kind of
argument, do a groups.google.com search of the sci.geo.satellite-nav
newsgroup. There you'll find endless argument, speculation, and
rationalization ranging from well informed to completely clueless.
There's surely more than ample ruminating there to satisfy anyone,
regardless of your orientation or clue level; it's surely not necessary
to do it all over again here.

Getting back to the original question (poor to non-existant AM
reception), I understand the idea of aperature and long wavelenths of
AM radio and the size of airplane windows - but what about the effect
of ALL the windows on a plane? Don't they create a much larger
effective apperature when you consider all of them?

A bit larger, yes. But the attenuation inside is still very high, since
the windows are extremely small and spaced very close, in terms of
wavelength. Sort of like the screen of a screen room.

And since the
plane isin't grounded, isin't the exterior shell of a plane
essentially transparent to all RF (ie it's just a re-radiator) because
it's not at ground potential?

No, being at "ground potential" plays no part in shielding. Currents and
fields on the outside aren't magically allowed to violate basic laws of
physics and migrate through a good conductor just because a shield isn't
at "ground potential". For that matter, a box that is at "ground
potential" at the bottom is nowhere near that potential a quarter
wavelength up the side. No shield over a small fraction of a wavelength
on a side could work if "ground potential" were a requirement. Yet
room-sized shielded enclosures are routinely used into the microwave
region. Try your own experiment. Turn your portable radio on, turn up
the volume, put it into a sealed can, set it on a stool, and see how
much you hear.

Roy Lewallen, W7EL

 

[Ether Hopper]

Well you have been referred to the FAA Regs and the Airline policies and
ignored them.

http://www.fordyce.org/scanning/scanning_info/scan_fly.html

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf/MainFrame?OpenFrameSet
Section 91.21
--------------------------------------------
So here is another URL we hope you read about GPS
http://gpsinformation.net/airgps/gpsrfi.htm

Just a snip:
There are documented cases of AM/FM radios causing interference with Avionic
systems and as a result, AM/FM radio receivers are generally prohibited.

You will be happy to learn of this quote;
"By design, (or happy accident), the "spurs" generated by a GPS generally
fall outside the communications frequencies used by Aircraft and so have not
been a problem even though a few "spurs" exist.
But SOME airlines do not permit the use of GPS receivers. Why is that if
they are "safe"?"

You will be unhappy with the answers. Hope you go to the URL for the answers

Here is one:
If a GPS is safe, why can't I use it on an airplane anyway, even if the
pilot says NO?
Answer:
This would be a) unwise, b) illegal and c) dangerous. Never presume that
you have more authority than the Captain of a ship! He is responsible for
the lives of his passengers and likely has knowledge and experience about
his aircraft and/or equipment and/or this particular flight that no one else
has.. The use of a GPS by a passenger is NOT worth a confrontation and a
possible visitation from the police or FBI when you land..

READ THE LAST SENTENCE AGAIN

Be safe, obey the law, stop guessing -- get educated and read these URL's


--
RF Gotta Go SomeWhere



"Some Guy" <Some@guy.com> wrote in message news:41BB8C6A.FD42C1E7@guy.com...

What a load of horse shit.

You guys are acting as if the engines and flight control surfaces of
an aircraft are intimately tied to the plane's radio receiver, and the
slightest odd or out-of-place signal that it receives is enough to
send any plane into a tail spin.

All this while the air travel industry is considering allowing
passengers to use their own cell phones WHILE THE PLANES ARE IN FLIGHT
by adding cell-phone relay stations to the planes and allowing any
such calls to be completed via satellite. So I guess the feeble
radiation by my FM radio (powered by 2 AAA batteries) is enough to
cause a plane to dive into the ocean, but the guy next to me putting
out 3 watts of near-microwave energy is totally safe.

What about my hand-held GPS unit? Any chance me using it (during all
phases of a flight, which I do routinely) will result in a one-way
ticket to kingdom come?

Getting back to the original question (poor to non-existant AM
reception), I understand the idea of aperature and long wavelenths of
AM radio and the size of airplane windows - but what about the effect
of ALL the windows on a plane? Don't they create a much larger
effective apperature when you consider all of them? And since the
plane isin't grounded, isin't the exterior shell of a plane
essentially transparent to all RF (ie it's just a re-radiator) because
it's not at ground potential?

 

[CW]

So, you contend that he cannot hear AM (MW) transmissions because the pilot
didn't give his permission?

"Ether Hopper" <EH@skip.net> wrote in message
newsiIud.4676$ve.1869@fed1read06...

No one has mentioned that in many cases you need the pilot's permission to
operate a radio or other electronic device for that matter on a commercial
airliner. That includes AM/FM radios.

Radio emissions may screw up the plane's avionics.

See URL:
http://www.fordyce.org/scanning/scanning_info/scan_fly.html

It sez:
"The FAA does not allow inflight use of walkie-talkies, radio controlled
toys, AM/FM radios, portable telephones, or portable television sets, all
of
which may affect aircraft radio and navigation equipment"

Also cruise ships may deny use of two way (FRS) or ham radios -- always
check with the communications officer.

For Hams always check with the person in charge on any commercial
transportation, busses, taxi's, ships planes etc.

Yeah yeah I know you did it without getting permission, but read the URL
as
to what airlines have published.

And I know from personal experience that some cruise lines do not allow
FRS
or ham radios transmissions.

--
RF Gotta Go SomeWhere



"nick smith" <NickS@ntlworld.com> wrote in message
news:MZHud.680$Uh.421@newsfe1-win.ntli.net...

"Geoff Glave" <nospam@nospam.com> wrote in message
news:HxHud.9448$eb3.8331@clgrps13...
Any explanation for this?

FM radio generally operates at longer range than AM radio, however it's
limited to line-of-sight. However, when you're 40,000 feet up you can
"see"
a lot of transmitters hence the FM signals.

Cheers,
Geoff Glave
Vancouver, Canada



I reckon you just answered the wrong question !!

The reason A.M. radio can not be received in a plane is that it is a
Faraday
cage to the (lower frequency) A.M
frequencies, whereas the VHF frequencies can just about get through the
windows.

There may be a bit of frequency / range issue as well but top band and
80
mtrs
gets across the pond so
I don't think this is the issue here...

Nick

 

[Dave VanHorn]

So, in all honesty, YOU can't really say how dangerous operation of an FM
receiver will be; but you KNOW that it's potentially harmful.

Given that the aircraft voice comms are just above the FM BCB, and the
typical first IF is 10.7 MHz, it's not too hard to imagine the LO sitting
right on the tower comm frequency.
You may only radiate a microwatt, but you're much closer to that antenna on
the aircraft than the tower is. Inverse square law makes it very easy for
you to win that contest.

This is a pointless argument though. It's a health and safety issue, and
you either follow the airline's rules, or I hope they boot you off the plane
(optionally, landing first for your convenience) It is just that simple.

 

[Dave VanHorn]

(5) Any other portable electronic device that the operator of the aircraft
has determined will not cause interference with the navigation or
communication system of the aircraft on which it is to be used.
(c) In the case of an aircraft operated by a holder of an air carrier
operating certificate or an operating certificate, the determination
required by paragraph (b)(5) of this section shall be made by that
operator of the aircraft on which the particular device is to be used. In
the case of other
aircraft, the determination may be made by the pilot in command or other
operator of the aircraft.

So in the case of an airline (air carrier) the airline makes the
determination to allow, NOT the pilot.
In a private plane, the pilot can decide to allow.

 

[Charles Newman]

"Ed Price" <edprice@cox.net> wrote in message
news:ymKud.23648$Af.3577@fed1read07...

"Ian Jackson" <IanJacksonRemoveThisBit@g3ohx.demon.co.uk> wrote in message
news:qQ5qidE8P1uBFw7f@g3ohx.demon.co.uk...
In message <piIud.4676$ve.1869@fed1read06>, Ether Hopper <EH@skip.net
writes
No one has mentioned that in many cases you need the pilot's permission
to
operate a radio or other electronic device for that matter on a
commercial
airliner. That includes AM/FM radios.

Radio emissions may screw up the plane's avionics.

Virgin included the use of radio receivers in their 'permitted list'
about
3 years ago. However, I do wonder about the use of the FM broadcast band
because the LO (tuned freq + 10.7MHz) can land up right on top of
something important in the ATC band.
Ian.

Virgin is a British Airline, so they can permit the operation of radios
once the plane leaves US airspace. Once the plane leaves US
airspace, it is no longer subject to FAA regulations.

 

[Radio Dawg]

That is what it says

But the average passenger wouldn't know the airline policies.
If so informed with written material, most won't read them anyway.

The pilot and flight attendants should know-- so asking is the reasonable
thing to do.

I queried several Airline pilots I know and they were all aware of their
Airline policies and stated they can't give permission but could state the
Airline policies and do so. AM/FM radios, GPS, FRS, GMRS, cell phones, Ham
radios and other devices were included as no no's on their Airlines.

Also Flight attendants are alerted to instruct passengers not to use certain
portable electronic devices so listed in their airline policies.

Yeah I know we are beating this thread to pieces, but maybe some readers
will desist in using a $10 Chinese radio that spews RFI all over the
aircraft.

Yes there is room for technical argument as how dangerous some devices are.
But the airlines have made their decisions based on the FAA regs.

Case closed

--
ID with held to protect the innocent



"Dave VanHorn" <dvanhorn@dvanhorn.org> wrote in message
news:0O6dnQISl7nGJybcRVn-tQ@comcast.com...

(5) Any other portable electronic device that the operator of the
aircraft has determined will not cause interference with the navigation
or communication system of the aircraft on which it is to be used.
(c) In the case of an aircraft operated by a holder of an air carrier
operating certificate or an operating certificate, the determination
required by paragraph (b)(5) of this section shall be made by that
operator of the aircraft on which the particular device is to be used. In
the case of other
aircraft, the determination may be made by the pilot in command or other
operator of the aircraft.

So in the case of an airline (air carrier) the airline makes the
determination to allow, NOT the pilot.
In a private plane, the pilot can decide to allow.

 

[TaxSrv]

Hey folks, let's not overdo the safety aspects here, so no one panics
if aboard an airliner and sees someone using a radio. I doubt any
device emitting small RF will be able to make comm reception
unreadable. Even if it did, there are then fallback procedures which
the pilot is required to know by heart, and the pilot is even
permitted to continue flight all the way to the gate without any
communication at all. Believe it or not, other aircraft may not have
to be vectored out of your way, or even informed about your problem.
But in reality, the pilot would simply peek at the coffee-stained nav
chart and dial up another controller on another freq and ATC will say
another frequency to come up on, or "stay with me."

For navigation on frequencies 108.00-117.95, besides being rather
strong signals, the nature of the modulation is such that interference
would have to be strong and be just so, to cause navigational error.
More likely there would a panel indication of an unusable signal --
because the receiver must be designed this way, and the pilot can
listen to the nav audio to hear the problem. The aircraft is also in
radar contact, so that if the pilot were to wander off course --
you're allowed a fairly wide margin -- ATC tells you if outside the
margin or not following a clearance if given a "direct." If you can't
rectify it, you simply ask for radar vectors, or switch to GPS nav, or
vice versa, or clearance to go direct to another nav beacon off the
nose, or GPS direct if equipped.

Now the same considerations apply to flying the approach and landing,
but the pilot would rather not have to deal with potential
interference to either nav or comm, especially if the airport is 1/2
mile visibility in fog. Thus, it's not too uncommon for the pilot to
grant permission to use a radio device only while in cruise.

Also, ATC will be able to tell the pilot that other aircraft are not
reporting a problem, a hint of possible interference from inside the
cabin. But has anybody ever heard a cabin announcement during flight
to turn off any devices?

Fred F.

 

[Radio Dawg]

Everything you have written is probably correct BUT
That is not the point -- The FAA and Airlines have regs and policies about
portable electronic equipment aboard an airliner PERIOD

And yes a sharp flight attendent did tell me to turn off a GPS unit.
--
ID with held to protect the innocent



"TaxSrv" <n3_eu@comcast.net> wrote in message
news:2YidnWP6YuJIHiHcRVn-sw@comcast.com...

Hey folks, let's not overdo the safety aspects here, so no one panics
if aboard an airliner and sees someone using a radio. I doubt any
device emitting small RF will be able to make comm reception
unreadable. Even if it did, there are then fallback procedures which
the pilot is required to know by heart, and the pilot is even
permitted to continue flight all the way to the gate without any
communication at all. Believe it or not, other aircraft may not have
to be vectored out of your way, or even informed about your problem.
But in reality, the pilot would simply peek at the coffee-stained nav
chart and dial up another controller on another freq and ATC will say
another frequency to come up on, or "stay with me."

For navigation on frequencies 108.00-117.95, besides being rather
strong signals, the nature of the modulation is such that interference
would have to be strong and be just so, to cause navigational error.
More likely there would a panel indication of an unusable signal --
because the receiver must be designed this way, and the pilot can
listen to the nav audio to hear the problem. The aircraft is also in
radar contact, so that if the pilot were to wander off course --
you're allowed a fairly wide margin -- ATC tells you if outside the
margin or not following a clearance if given a "direct." If you can't
rectify it, you simply ask for radar vectors, or switch to GPS nav, or
vice versa, or clearance to go direct to another nav beacon off the
nose, or GPS direct if equipped.

Now the same considerations apply to flying the approach and landing,
but the pilot would rather not have to deal with potential
interference to either nav or comm, especially if the airport is 1/2
mile visibility in fog. Thus, it's not too uncommon for the pilot to
grant permission to use a radio device only while in cruise.

Also, ATC will be able to tell the pilot that other aircraft are not
reporting a problem, a hint of possible interference from inside the
cabin. But has anybody ever heard a cabin announcement during flight
to turn off any devices?

Fred F.

 

[Dave Bushong]

TaxSrv wrote:

Hey folks, let's not overdo the safety aspects here, so no one panics
[...]

Fred,

Nearly all aircraft accidents are caused by a series of unlikely events
all happening together, none of which by itself would be a problem.

Would you want to add one more "unlikely event" to your next flight? Do
you have life insurance?

73,
Dave

(to keep this on topic, I will say this: last week my garage door
snagged the corona tip on my ATAS-120 and broke something inside the
tuning section, and bent my trunk lid. A $300 mistake. Damn.)

 

[Dave VanHorn]

Our club repeater also ended up interfering with the local tower.

It seems that the transmitter PLL was unstable, and "hopping" between that
frequency, and ours.
We were clearly audible in their recordings.

Lest any "experts" step in and claim that you can't receive FM on an AM
receiver, I'd ask them to consider what effect the passband filter of the AM
receiver's IF might have on the FM signal as it deviates from side to
side....

I hit the magic codes and took the repeater down, once we determined that
this was indeed the source.

A re-tweak of the transmit PLL, and a stub filter cut to pass 146.730 and
reject the tower frequency, cured the problem, and insured that if it ever
happens again, they probably won't hear us. The tower now has our phone
numbers in their books, in case there is ever another problem. The tower
complimented our rapid and assertive handling of the problem in their
closing letter to the FCC.

Repeater cans don't do much for signals that are far out of band.

 

[Dave Platt]

Our club repeater also ended up interfering with the local tower.

It seems that the transmitter PLL was unstable, and "hopping" between that
frequency, and ours.
We were clearly audible in their recordings.

Ouch. That'd be categorized as a "double-plus ungood" for certain!

Lest any "experts" step in and claim that you can't receive FM on an AM
receiver, I'd ask them to consider what effect the passband filter of the AM
receiver's IF might have on the FM signal as it deviates from side to
side....

I believe the magic words are "slope detection". The resulting audio
on the AM receiver isn't great (it's often distorted) but it's
certainly there.

I hit the magic codes and took the repeater down, once we determined that
this was indeed the source.

A re-tweak of the transmit PLL, and a stub filter cut to pass 146.730 and
reject the tower frequency, cured the problem, and insured that if it ever
happens again, they probably won't hear us. The tower now has our phone
numbers in their books, in case there is ever another problem. The tower
complimented our rapid and assertive handling of the problem in their
closing letter to the FCC.

Well done!

--
Dave Platt <dplatt@radagast.org> AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[Some Guy]

Dave Bushong wrote:

[Dramatic generalization mode on]

Nearly all aircraft accidents are caused by a series of unlikely
events all happening together, none of which by itself would be
a problem.
[Dramatic generalization mode off]

Nice sweeping piece of dis-information there buddy.

How about this: Nearly all aircraft accidents are caused by a single
failure in a single component or a single failure to do something.
Pitot tubes that are taped over. Fuel tanks that explode. Structural
failure that causes entire pieces of fuselage to peel off while in
flight. Fuel leaks that turn large jets into gliders. Cabin fires
caused by the overload of a single wire powering the entertainment
system. Air pressure equalization valves that bleed cabin air
rendering the occupants unconscious and results in a ghost plane
flying thousands of miles before crashing. Failure to de-ice.
Overloading resulting in stalling upon take-off. Failure to secure
cargo upon takeoff. Being struck in the fuel tank by a piece of
debris on the runway kicked up by the tires. An engine ingesting a
flock of birds. A shipment of improperly-disarmed oxygen generators
placed in the cargo hold. Lack of proper lubrication of tail
jack-screws. Tail fins that are not as strongly connected to the
fuselage as they should be. Need I continue?

A series of events will surely happen AFTER any of those incidents,
none of which are either unlikely or unexpected, and by and large
would have no effect on the outcome.

Will the in-flight use of an FM radio EVER cause a plane to run out of
fuel? Or cause a sudden ice build-up on the wings? Or blow out a
tire upon landing? Or an overload of the electrical system leading to
a fire? Will the feeble RF emitted by the LO even be detectable
OUTSIDE the plane, where the plane's antennas are located?

If you read the various documents on the web relating to issues of
in-flight use of PED's (personal electronic devices) it's clear that

1) The FAA and NTSB are either negligent or a bunch of cowards for not
forcing the AIRCRAFT MANUFACTURERS to determine the level of
susceptibility of their planes to PED's. Instead the issue is pawned
off to the aircraft operators when logically it should be the airplane
makers!

2) The use of cell phones (analog and perhaps more frequently GSM)
seems to have the most influence of any PED. The next most frequent
culprit seems to be laptop computers.

3) No incidence of communication failure or disruption seems to have
ever been documented by a passenger's FM radio receiver.

4) MANY MANY incidences of navigation equipment errors caused by
improper installation / connection of the equipment, or interference
caused by one of the plane's other systems where these were first
attributed to a PED.

5) Planes have to fly near high-power commercial radio and TV
transmission towers. They fly through the beams of powerful radar
signals. They get struck by lightning. There are those that say that
for a (commercial jet) to be certified there is no way that a
certified plane could be susceptible to the stray RF given off by
PED's (at least PED's that are non-intentional radiators).

6) The authorities would probably not admit it, but the ban or
restrictions on PED use in planes probably has more to do with
insurance/liability reasons, or passenger distraction reasons, than it
does for technical (interference) reasons.

PED's are here to stay. There will be more of them, and people will
use them wherever they are. It makes just as much sense to ban them
or perform half-ass on-board supervision on a plane for these devices
as it is to ban them from cars. PED's used cars cause injury and
death each year (due to driver in-attention). Instead of banning
radios, phones, and entertainment systems in cars, they instead come
from the factory with them installed! Where's your crusade against
that situation? Where are your dire warnings here?

Would you want to add one more "unlikely event" to your next
flight?

Nothing caused by or brought on board by a passenger (short of
alcohol, a gun, a bomb, or otherwise a strong intent to do harm) will
or has ever caused anything bad to happen on a plane or to a plane.
No gun ever brought on board (and there have been MANY!) has ever
discharged. No can of hairspray has ever exploded in the cargo hold.

There is relatively little variety in the types, makes or models of
commercial airplanes flying today. There is a high degree of
uniformity in construction of these vehicles. There have been
millions of flights over the past, say 20 years. There have been many
hundred million passengers carried by these planes. There surely has
been ample opportunity for all sorts of PED's to be used on these
planes (surreptitiously or with consent). If any particular plane
model (or even specific plane) had a systemic or inherent
susceptibility to a PED, it would have been recognized by now.