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AM radio reception inside passenger planes?

T

TaxSrv

Jan 1, 1970
0
Ed Price said:
...
Stick to assertions that
have a basis in fact and not just in your mind.
...
Fred, your world is much different than any I have ever seen.

Ed
wb6wsn

My world is as an instrument rated pilot and one who services aircraft
avionics. And you must have missed my other post where I said PEDs
should be off at all times.

Fred F.
 
E

Ed Price

Jan 1, 1970
0
phoneguy99 said:
SNIP



On one flight, a few years earlier still, WITH the ok from the flight deck
(you know, in those friendlier years when you could say 'hi' through the
open cockpit door when you were coming out of the bathroom) I used my
FT-470 handie for a few mins. The pilot knew what ham radio was, knew I
was going to be on UHF (because I told him that's where I would try for a
quick QSO) and he very politely said "Sure, but only for 5 minutes, then
turn it off. What seat are you in?" I thanked him kindly, returned to my
window seat, and did manage to get into some repeater in Maine for about a
minute or two. The funny thing was he was in the galley as we were getting
off the plane, I thanked him again, and he asked if I had any luck, I said
'yep' and asked him if I came over anything up front. He smiled and said
"Nope, and we were up there looking to see if you would."

The purpose of my sharing this snippet from many years ago is not to
illustrate there's no danger in using a receiver (or in this case, a low
power transmitter) while on a plane, but using one does not automatically
imply you're going to write off the comm/nav systems.

My $.02


It also illustrates the safety concern. Although there were no observed
improper responses from the aircraft avionics, "we were up there looking to
see if you would" (cause a problem) is very disturbing. You added to the
pilots' workload for several minutes, involving them in an interesting
science project. The cockpit is normally a very busy place, so what tasks
were slighted to allow time for your project?

How would you have felt if the flight crew was diverting some of their time
to help somebody with a tough crossword puzzle? Was a Maine QSO worth it
all? I'd have given you a whole quarter to pull the battery from your HT!

Ed
wb6wsn
 
J

J.Hoekstra

Jan 1, 1970
0
Reception of radiosignals inside a Faradaycage is limited to frequencies
that are smaller then the holes in the cage.
 
B

Bob Myers

Jan 1, 1970
0
Some Guy said:
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.

Not at all; however, there IS obviously a connection between
various flight control functions (such as, say, the autopilot) and
the information given by the avionics (esp. "nav" radios using
ground-based sources such as VORs, etc.). It's not going to
"send any plane into a tail spin", but it can certainly cause some
problems.
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.

You DO realize that these are on very different frequencies, and
that the emissions of an FM superheterodyne radio are very
likely to fall right in the aviation band, don't you? Hint: if you have
to go look up "superheterodyne" to understand this question, I
have serious doubts regarding your qualifications to comment on it.
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?

No. It's not the TOTAL area of the "apperatures" [sic] that
is important, it's the size of the individual openings. If this were
not so, then a conductive mesh could never be effective as a
shield.
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. "Ground potential" has absolutely nothing to do
with it. Hint: what do you think is the RF environment
within a perfectly conducting sealed enclosure, with
respect to outside sources, even if that enclosure is
completely isolated from any other surface or conductor?

Bob M. (KC0EW)
 
B

Bob Myers

Jan 1, 1970
0
Charles Newman said:
What is a Pitot tube anyway? I have seen a switch for most aircraft
in Flight Simulator marked "Pitot Heat", what is that?

A pitot tube is a tube which protrudes from the aircraft
body into the path of the air through which the aircraft is
flying. They are used for such things as determining airspeed
(which is the speed of the aircraft through the air, not over
the ground), and in some meteorological conditions are
prone to becoming clogged with ice. Hence, "pitot heat"
is just that - the switch in question controls a heater (most
often, electric) built into the pitot tube, which keeps in clear
of ice. Losing pitot pressure due to having the damn thing
plugged up is generally considered a Bad Thing, and
unfortunate events have been known to follow such an
occurence.

Bob M.
 
D

Dave Holford

Jan 1, 1970
0
cabin. But has anybody ever heard a cabin announcement during flight
to turn off any devices?

Fred F.

There have been numerous postings in various scanner, shortwave and ham
groups by people who have been ordered to turn off their radio and other
PEDs.
More than one person has been ordered off, or met by the authorities on
landing and at least one passenger who refused to turn off a cellphone ended
up with some jail time after landing in the U.K. - it was pretty widely
reported a year or so ago.

Dave
 
D

Dave Holford

Jan 1, 1970
0
My world is as an instrument rated pilot and one who services aircraft
avionics. And you must have missed my other post where I said PEDs
should be off at all times.

Fred F.

The I presume you specified AM because the LO operates outside aviation
frequencies (now that LORAN A is gone), unlike the LO in an FM broadcast
receiver which covers the VHF localizer and VOR frequencies very nicely.

Dave
 
D

Dave Holford

Jan 1, 1970
0
I can't provide technical details of the operation because I don't know
them; but I am familiar with a number of totally RF screened environments
where use of electronic devices are tightly controlled. However, internal
relays are used to permit operation of cell phones - which I always
understood were specific models which had been certified for such use.

Dave
 
S

Some Guy

Jan 1, 1970
0
Dave said:
I am familiar with a number of totally RF screened environments
where use of electronic devices are tightly controlled.
However, internal relays are used to permit operation of cell
phones

The point was not how the planes are being equipped to handle
in-flight cell-phone use.

The point was that consideration is being made to allow cell phones to
be used while the planes are in flight. That intentional radiating
PED's are even being considered for in-flight use when so much hype
and concern is being given to the weak radiation potential of some
non-intentional radiators like am/fm radios.

BTW, what is the potential of the local oscillators of small hand-held
LCD-screen TV's to overlap with aviation frequencies?
 
D

Dave VanHorn

Jan 1, 1970
0
On the way back, I spoke with a commercial pilot who was deadheading, on
this issue.
He said that it's not all that unusual to hear radio interference once they
have allowed the devices on, but when they are in cruise, they aren't
normally doing any urgent communications, so it isn't much of an issue. If
something comes up, then they will pass the word to shut down the PEDs.

On takeoff and landing though, the comms are much more rapid, and the
consequences of missing one transmission are much higher. They need to hear
all the comms, not just between themselves and the tower, but what the other
pilots are saying as well. Add to this, the fact that aircraft comms are
AM, which is inherently muddy, and it's easy to see why they take the extra
precautions.
 
B

Bob Myers

Jan 1, 1970
0
Some Guy said:
The point was that consideration is being made to allow cell phones to
be used while the planes are in flight. That intentional radiating
PED's are even being considered for in-flight use when so much hype
and concern is being given to the weak radiation potential of some
non-intentional radiators like am/fm radios.

Because, as has already been pointed out, of the
differences in emission characteristics (and specifically
the frequency ranges likely to be affected) of the two
classes of devices.
BTW, what is the potential of the local oscillators of small hand-held
LCD-screen TV's to overlap with aviation frequencies?

I believe they should be somewhat less than is the case
with an FM receiver, but they're still a bad idea for
the same reason. Note that the analysis of the likely
frequencies provided so far has dealt solely with the
first-order effects of the receiver's local oscillator; we
have NOT discussed harmonics or other unwanted
emissions.

The problem is most obvious with FM receivers because
the standard 1st LO frequency is 10.7 MHz, and the
top of the FM broadcast band is adjacent to the bottom
of the aviation band (108 MHz) - which means that
simply adding the LO frequency to standard FM
broadcast frequencies can take you instantly into overlap
with the bottom 10.7 MHz of the aviation band (and
unfortunately, that's where a lot of the radionavigation
systems within that band tend to be). But this does
not mean that receivers for other services would not
cause similar problems. VHF television covers
frequencies below and above both FM and
aviation (two bands, 54-88 MHz for channels 2
through 6, and 174 to 216 MHz for channels 7
through 13). It is certainly very possible that receivers
intended for these bands would emit in the aviation
band. Other adjacent services that may be of concern
include public-service and commerical communication
bands (i.e., police scanners) and the 2-meter amateur
band.

Bob M.
 
T

TaxSrv

Jan 1, 1970
0
Dave VanHorn said:
They need to hear
all the comms, not just between themselves and the tower, but what
the other pilots are saying as well. Add to this, the fact that aircraft
comms are AM, which is inherently muddy, and it's easy to see why
they take the extra precautions.

The design of newer comms doesn't help either. If they have automatic
squelch, set to break at say 1uV RF in, then obviously it doesn't take
much interference to break squelch. Then, they also may have "audio
leveling" -- a great feature when commonly using headphones -- but the
effect there will be to take a few uV of noise and amplify the audio
component to the level you hear when ATC hits you with as much as 50W,
and it's heard constantly between transmissions, to be hopefully
silenced when ATC talks. But not necessarily the case in monitoring
comms of other aircraft, where especially general aviation,
less-than-properly-functional 7W units can be relatively weak.

Fred F.
 
W

Watson A.Name - \Watt Sun, the Dark Remover\

Jan 1, 1970
0
Geoff Glave said:
FM radio generally operates at longer range than AM radio,

Nonsense! AM radio stations can be heard for thousands of miles, FM for
'line of sight', which is usually less than a hundred miles.
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.

Nonsense! The passenger is sitting in a Faraday Cage, a fuslage made of
alumninum. The FM wavelength is short enough to go thru the windows,
but mot the AM signals.
 
W

Watson A.Name - \Watt Sun, the Dark Remover\

Jan 1, 1970
0
Ian Jackson said:
The window holes are much too small to let the much longer wavelengths
of the 'AM' signals through. The body of the plane is a very effective
screen. The 'FM' signals can squeeze in, but it helps if you have a
window seat. I've also listened to SW in the middle of the Atlantic.

Flying from the UK to Florida, on the other side of the Atlantic the
first FM stations you hear are usually speaking French (from Quebec)
It's quite alarming!
Ian.
--

If you stretch a string on a globe from London to Florida, it will show
the 'great circle' route that's the shortest, and that should be your
plane's path, barring storme, hurricanes, etc. You'll see that it comes
really close to the eastern Canadian provinces.
 
W

Watson A.Name - \Watt Sun, the Dark Remover\

Jan 1, 1970
0
Richard Clark said:
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

If you make your own TRF receiver, with no LO, it won't interfere with
anything. In fact, you can then put an AM detector in it, and also
listen to the aircraft chatter.

Another way is to listen to stations at or below 97.3 MHz, which would
keep the LO at 108 MHz or below.
 
W

Watson A.Name - \Watt Sun, the Dark Remover\

Jan 1, 1970
0
Some Guy said:
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.

No, the laws say that you can be arrested for breaking them, and one way
to break them is to use a FM radio while the aircraft is flying.
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.

You don't know what you're talking about. With the attitudes of the air
marshals nowadays, making airliners turn around and go back to their
departure point just because a passenger is unruly, there is a high
probability that one of them is flying along on your flight, and if he
sees an earphone hanging out of your ear, you might be that unruly
passenger they arrest at the departure point. Especially with your
nasty attitude!
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?

Geez, what a TWERP! You can't add two and two without jumping to
conclusions! A rational conversation with you is nearly impossible.
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?

You're even dumber than I had thought. Look up Faraday Shield.
Here, try this: http://www.physlink.com/Education/AskExperts/ae176.cfm
You don't have to worry about a ground for it to work. Duh.
 
E

Ed Price

Jan 1, 1970
0
Watson A.Name - "Watt Sun said:
If you make your own TRF receiver, with no LO, it won't interfere with
anything. In fact, you can then put an AM detector in it, and also
listen to the aircraft chatter.

Another way is to listen to stations at or below 97.3 MHz, which would
keep the LO at 108 MHz or below.

Like maybe putting the LO at about 80 MHz, so that the 3rd harmonic of the
LO drops into the UHF navcom band?

Ed
wb6wsn
 
E

Ed Price

Jan 1, 1970
0
Watson A.Name - "Watt Sun said:
No, the laws say that you can be arrested for breaking them, and one way
to break them is to use a FM radio while the aircraft is flying.


You don't know what you're talking about. With the attitudes of the air
marshals nowadays, making airliners turn around and go back to their
departure point just because a passenger is unruly, there is a high
probability that one of them is flying along on your flight, and if he
sees an earphone hanging out of your ear, you might be that unruly
passenger they arrest at the departure point. Especially with your
nasty attitude!


Geez, what a TWERP! You can't add two and two without jumping to
conclusions! A rational conversation with you is nearly impossible.


You're even dumber than I had thought. Look up Faraday Shield.
Here, try this: http://www.physlink.com/Education/AskExperts/ae176.cfm
You don't have to worry about a ground for it to work. Duh.

He's not dumber than "I" thought!

Ed
wb6wsn
 
E

Ed Price

Jan 1, 1970
0
-dressed baby. By the time you turn the child?s breast into
cutlets, it will be indistinguishable. The taste of young human,
although similar to turkey (and chicken) often can be wildly
different depending upon what he or she has consumed during its
10 to 14 months of life...

4 well chosen cutlets (from the breasts of 2 healthy neonates)
2 large lemons (fresh lemons always, if possible)
Olive oil
Green onions
Salt
pepper
cornstarch
neonate stock (chicken, or turkey stock is fine)
garlic
parsley
fresh cracked black pepper

Season and sauté the cutlets in olive oil till golden brown, remove.
Add the garlic and onions and cook down a bit.
Add some lemon juice and some zest, then de-glaze with stock.
Add a little cornstarch (dissolved in cold water) to the sauce.
You are just about there, Pour the sauce over the cutlets,
top with parsley, lemon slices and cracked pepper.
Serve with spinach salad, macaroni and cheese (homemade) and iced tea...



Spaghetti with Real Italian Meatballs

If you don?t have an expendable bambino on hand,
you can use a pound of ground pork instead.
The secret to great meatballs, is to use very lean meat.

1 lb. ground flesh; human or pork
3 lb. ground beef
1 cup finely chopped onions
7 - 12 cloves garlic
1 cup seasoned bread crumbs
½ cup milk, 2 eggs
Oregano
basil
salt
pepper
Italian seasoning, etc.
Tomato gravy (see index)
Fresh or at least freshly cooked spaghetti or other pasta

Mi
 
E

Ed Price

Jan 1, 1970
0
cup shredded cabbage
1 cup bean sprouts
5 sprigs green onion, finely chopped
5 cloves minced garlic
4-6 ounces bamboo shoots
Sherry
chicken broth
oil for deep frying (1 gallon)
Salt
pepper
soy & teriyaki
minced ginger, etc.
1 tablespoon cornstarch dissolved in a little cold water
1 egg beaten

Make the stuffing:
Marinate the flesh in a mixture of soy and teriyaki sauces
then stir fry in hot oil for till brown - about 1 minute, remove.
Stir-fry the vegetables.
Put the meat back into the wok and adjust the seasoning.
De-glaze with sherry, cooking off the alcohol.
Add broth (optional) cook a few more minutes.
Add the cornstarch, cook a few minutes till thick,
then place the stuffing into a colander and cool;
2 hours
Wrap the rolls:
Place 3 tablespoons of stuffing in the wrap, roll tightly -
corner nearest you first, fold 2 side corners in,
wrap till remaining corner is left.
Brush with egg, seal, and allow to sit on the seal for
a few minutes.
Fry the rolls:
325° if using egg roll wraps, 350° for spring roll wraps.
Deep fry in peanut oil till crispy golden brown, drain on paper towels.



Lemon Neonate

Turkey serves just as well, and in fact even looks a bit like a
well-dressed baby. By the time you turn the child?s breast into
cutlets, it will be indistinguishable. The taste of young human,
although similar to turkey (and chicken) often can be wildly
different depending upon what he or she has consumed during its
10 to 14 months of life...

4 well chosen cutlets (from the breasts of 2 healthy neonates)
2 large lemo
 
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