AM radio reception inside passenger planes?
Some Guy
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?
Geoff Glave
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
Ian Jackson
<nos...@nospam.com> writes
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.
--
nick smith
"Geoff Glave" <nos...@nospam.com> wrote in message
news:HxHud.9448$eb3.8331@clgrps13...
I reckon you just answered the wrong question !!
The reason A.M. radio can not be received in a plane is that it is a Faraday
cage to the (lower frequency) A.M
frequencies, whereas the VHF frequencies can just about get through the
windows.
There may be a bit of frequency / range issue as well but top band and 80 mtrs
gets across the pond so
I don't think this is the issue here...
Nick
Ether Hopper
operate a radio or other electronic device for that matter on a commercial
airliner. That includes AM/FM radios.
Radio emissions may screw up the plane's avionics.
See URL:
http://www.fordyce.org/scanning/scanning_info/scan_fly.html
It sez:
"The FAA does not allow inflight use of walkie-talkies, radio controlled
toys, AM/FM radios, portable telephones, or portable television sets, all of
which may affect aircraft radio and navigation equipment"
Also cruise ships may deny use of two way (FRS) or ham radios -- always
check with the communications officer.
For Hams always check with the person in charge on any commercial
transportation, busses, taxi's, ships planes etc.
Yeah yeah I know you did it without getting permission, but read the URL as
to what airlines have published.
And I know from personal experience that some cruise lines do not allow FRS
or ham radios transmissions.
--
RF Gotta Go SomeWhere
"nick smith" <Ni...@ntlworld.com> wrote in message
news:MZHud.680$Uh....@newsfe1-win.ntli.net...
Ian Jackson
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.
--
Dave Bushong
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
Ether Hopper
--
RF Gotta Go SomeWhere
"Ether Hopper" <E...@skip.net> wrote in message
news:piIud.4676$ve.1869@fed1read06...
Ed Price
"Ian Jackson" <IanJacksonR...@g3ohx.demon.co.uk> wrote in message
news:qQ5qidE8...@g3ohx.demon.co.uk...
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
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" <edp...@cox.net> wrote in message
news:ymKud.23648$Af.3577@fed1read07...
Richard Clark
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
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
>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.
Roy Lewallen
> 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
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" <So...@guy.com> wrote in message news:41BB8C6A...@guy.com...
CW
didn't give his permission?
"Ether Hopper" <E...@skip.net> wrote in message
news:piIud.4676$ve.1869@fed1read06...
Ed Price
Yes, you are a wholesale distributor. Further, you are a loud-mouthed,
egocentric nitwit with a knowledge of physics equivalent to a smart gerbil.
You should be allowed on an aircraft only as freight.
Ed
wb6wsn
Dave VanHorn
> So, in all honesty, YOU can't really say how dangerous operation of an FM
> receiver will be; but you KNOW that it's potentially harmful.
Given that the aircraft voice comms are just above the FM BCB, and the
typical first IF is 10.7 MHz, it's not too hard to imagine the LO sitting
right on the tower comm frequency.
You may only radiate a microwatt, but you're much closer to that antenna on
the aircraft than the tower is. Inverse square law makes it very easy for
you to win that contest.
This is a pointless argument though. It's a health and safety issue, and
you either follow the airline's rules, or I hope they boot you off the plane
(optionally, landing first for your convenience) It is just that simple.
Dave VanHorn
> has determined will not cause interference with the navigation or
> communication system of the aircraft on which it is to be used.
> (c) In the case of an aircraft operated by a holder of an air carrier
> operating certificate or an operating certificate, the determination
> required by paragraph (b)(5) of this section shall be made by that
> operator of the aircraft on which the particular device is to be used. In
> the case of other
> aircraft, the determination may be made by the pilot in command or other
> operator of the aircraft.
So in the case of an airline (air carrier) the airline makes the
determination to allow, NOT the pilot.
In a private plane, the pilot can decide to allow.
Charles Newman
> news:qQ5qidE8...@g3ohx.demon.co.uk...
> > In message <piIud.4676$ve.1869@fed1read06>, Ether Hopper <E...@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
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" <dvan...@dvanhorn.org> wrote in message
news:0O6dnQISl7n...@comcast.com...
Wes Stewart
<dvan...@dvanhorn.org> wrote:
|
|> 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.
Correct. Let me offer a slightly different but illustrative example.
Since this is cross-posted to some non-ham groups, bear with me. In
the 1960's I operated my amateur station on the two-meter (144 MHz)
band using several hundred watts of AM and directional antennas.
I'm in Tucson where we have both a commercial airport and D-M AFB. An
acquaintance of mine, also a ham, was the FAA tower chief at Tucson
International.
One day he calls me on the phone and says that the tower guys at D-M,
knowing he was a ham, called him first rather than the FCC, to report
that I was interfering with their tower communications.
To make an involved detective story short, it turned out that another
ham, who lived just outside the AFB was using a Heathkit "Twoer". The
Twoer used a super-regenerative receiver and was picking up my signal
and re-radiating it on the tower frequencies. I was getting blamed
for the other guy's illegal transmissions.
Considering that this technology is probably used in more receivers
today than any other type (garage door openers, computer wireless
links, etc.) if I'm flying, I hope they are all turned off.
TaxSrv
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
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...@comcast.net> wrote in message
news:2YidnWP6YuJ...@comcast.com...
Dave Bushong
> 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
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
>
>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 <dpl...@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
[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.
Henry Kolesnik
"Some Guy" <So...@Guy.com> wrote in message news:41BC9EBE...@Guy.com...
Charles Newman
"Some Guy" <So...@Guy.com> wrote in message news:41BC9EBE...@Guy.com...
>
> [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
What is a Pitot tube anyway? I have seen a switch for most aircraft
in Flight Simulator marked "Pitot Heat", what is that?
Dave Bushong
Angry crap.
TaxSrv
> Nearly all aircraft accidents are caused by a series of unlikely
events
> all happening together, none of which by itself would be a problem.
I'll bet there's no record of a U.S. airline accident caused by faulty
navigation equipment for any reason, or at least excluding maybe the
early years. General aviation, yes.
> Would you want to add one more "unlikely event" to your next
flight?
I have no problem with any airline with a flat "no" policy on this,
because things do happen even if rarely. NASA gathers the PED
incident data, and over a 14-year period, there have been less than
100 events, mostly in cruise, most not classed as potentially serious.
The reason they were reported is because the equipment told the pilot
about it, and often ATC did so too. Also, NASA has to take the
pilot's word for it that the anomaly was caused by a PED.
Fred F.
Radio Dawg
http://www.grc.nasa.gov/WWW/K-12/airplane/pitot.html
Re Pitot Heat -- see URL:
http://www.allstar.fiu.edu/aero/PSSI.htm
Sez
The system shown employs a heated pitot tube to prevent ice formation, a
necessary feature for flight in instrument conditions.
--
ID with held to protect the innocent
>
chuck
Boeing has investigated alleged interference from portable electronic
devices (PEDs) and concluded:
"As a result of these and other investigations, Boeing has not been able
to find a definite correlation between PEDs and the associated reported
airplane anomalies."
You can look this up at:
http://www.boeing.com/commercial/aeromagazine/aero_10/interfere_textonly.html
Aero 10 - Interference from Electronic Devices
Here's another one:
http://www.rvs.uni-bielefeld.de/publications/Incidents/DOCS/Research/Rvs/Article/EMI.html
Electromagnetic interference with aircraft systems
Dave VanHorn
Well, I'll be flying to philly again tuesday.
My dualband HT goes in my breifcase, but with the battery detached during
flight.
phoneguy99
TaxSrv wrote:
> cabin. But has anybody ever heard a cabin announcement during flight
> to turn off any devices?
>
> Fred F.
YES.
I was on a flight from Toronto to Tampa a few years ago and somewhere
over the Carolinas the pilot came on the PA and calmly informed us they
have spent the last 45 mins trying to find the source of a buzzing noise
on their radios. (He also reinforced the fact that they were all still
working, but there was a buzzing noise on the audio.) He politely told
everyone to turn off any electronic devices they may be using. The
flight attendants quickly verified passenger compliance a few minutes
later. About 10 mins after that, he came on the PA to say it was gone
and instructed everyone to leave them off for the duration of the
flight, not that there was any danger, but it was distracting to have a
constant buzzing coming over the radio.
I did notice a couple of laptops had been fired up, but sitting in your
seat is not exactly an ideal vantage point to see what everyone else was
doing.
Do I think someone's radio is going to make the plane fall from the sky?
Of course not. Is there a remote possibility it could cause birdies or
other RF anomalies that 'could' affect things? Sure.
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
Ed Price
> 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,
Your doubts do not stand up to empirical evidence. Stick to assertions that
have a basis in fact and not just in your mind.
The whole point is to not weaken the chain of redundant flight safety
features just to allow a piece of meat cargo to be electronically
entertained.
> 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.
And all passengers will immediately comply, because they are all concerned
about not creating a dangerous electronic environment. Games will be halted,
spreadsheets closed, and porn movies terminated. Cabin attendants will
notice immediate 100% compliance, and will not be distracted from other
duties to repeatedly remind, cajole or threaten recalcitrant passengers.
Fred, your world is much different than any I have ever seen.
Ed
wb6wsn
Ed Price
"Some Guy" <So...@Guy.com> wrote in message news:41BC9EBE...@Guy.com...
>
> [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.
>
> 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?
It's so damn complicated that nobody can answer the question. Airliners are
going in the direction of all-electronic flight control and management
systems. Somebody's LO won't affect fuel consumption, uhh, unless it affects
the microprocessor or sensors controlling the engine. It's unlikely, a lot
of work goes toward making it extremely unlikely. But remember, I said
unlikely, not impossible.
Ice on the wings? What controls the de-icing boot?
Blow a tire? Is the braking circuit all-mechanical, or do you have something
akin to power boost and anti-lock sensing?
Is the LO detectable outside the fuselage, near the antennas? YES, damn it,
YES. I have measured it, with calibrated field strength meters. Don't give
me your damn dumb opinions when I have seen the results myself. And is the
LO emission strong enough to degrade or deny a navcom signal. YES or MAYBE
or COULD BE. It depends on the passenger's radio, how he holds it, is he
next to a window, is the fuselage unusually leaky to RF, what seat is the
passenger in, what station is the radio tuned to, are the batteries new or
weak, how weak is the navcom signal, what is the attitude of the aircraft,
is the navcom receiver getting old, even are there multiple passenger
receivers acting on the navcom (if they are all like you, how many of 300
passengers will have personal electronics running?).
The POSSIBILITY of interference is undeniable. The PROBABILITY is very
difficult to predict. The safe course is to deny you your entertainment for
several hours to ensure maximum safety. Is that too much to ask of you?
Ed
wb6wsn
TaxSrv
>...
> 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.
Ed Price
"chuck" <ch...@nospam.net> wrote in message
news:XK3vd.1528$2J2...@newsread2.news.atl.earthlink.net...
> Dave, try these:
>
> Boeing has investigated alleged interference from portable electronic
> devices (PEDs) and concluded:
>
> "As a result of these and other investigations, Boeing has not been able
> to find a definite correlation between PEDs and the associated reported
> airplane anomalies."
>
> You can look this up at:
>
> http://www.boeing.com/commercial/aeromagazine/aero_10/interfere_textonly.html
> Aero 10 - Interference from Electronic Devices
>
> Here's another one:
>
> http://www.rvs.uni-bielefeld.de/publications/Incidents/DOCS/Research/Rvs/Article/EMI.html
> Electromagnetic interference with aircraft systems
Not to cast aspersions on Boeing research, as they are quite reputable, but
if they had found correlatable evidence of PED's interfering with avionics,
who gets sued? The passenger, a Hong Kong radio manufacturer, or the
aircraft builder?
In any case, the reports of interference keep coming in, despite the
difficulty of replicating the problem. Obviously, the problem is rare and
elusive, but, as in most Electromagnetic Compatibility issues, the easiest,
surest, and cheapest cure is to control the source of the problem.
Just turn off ALL passenger electronics for the duration of the flight. Read
a book for 2 hours, and let your kid kick the seat in front of him.
Ed
wb6wsn
Ed
wb6wsn
Ed Price
>
> Well, I'll be flying to philly again tuesday.
> My dualband HT goes in my breifcase, but with the battery detached during
> flight.
>
>
The first note of personal responsibility and common sense yet seen in this
thread. Congratulations!
Ed
wb6wsn
Ed Price
"phoneguy99" <phoneguy...@unspamsympatico.ca> wrote in message
news:fh5vd.2407$%p1.2...@news20.bellglobal.com...
>
> TaxSrv wrote:
>> cabin. But has anybody ever heard a cabin announcement during flight
>> to turn off any devices?
>>
>> Fred F.
>
> YES.
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
Theplanters95
make some contacts. My friend announces that we are lost. It took about 10
minutes before I found a landmark and got him following a road to the airport.
My friend believes that the HT interfered with his radio compass and put use
off course. After the HT was turned off and time was allowed, the compass
returned to normal. I don't know how it happened, but it did! Now I just
carry my ht on the plane and do not operate!
Randy ka4nma
Wes Stewart
(Theplanters95) wrote:
Despite my concerns expressed earlier I will confess to contacting a
couple of my buddies using my 2-meter handi from an aircraft, with the
pilot's permission.
'Course, he was also a ham and we were flying in a sailplane that had
a couple of light bulbs for electronics. [g] The only way to fly.
Dave VanHorn
> 'Course, he was also a ham and we were flying in a sailplane that had
> a couple of light bulbs for electronics. [g] The only way to fly.
Well, if one of the light bulbs goes out, they'll blame it on the nearest
ham :)
Seems pretty safe, but I still wouldn't do it without permission.
I'm like that when I drive.
I'm in the left seat, it's my car and my ass, and I make the decisions.
I have actually had a passenger throw a fit because I wouldn't make a left
turn that I wasn't convinced was safe, in the 1-2 seconds I had to look at
it when the passenger hollered "turn left here". He got to walk home.
Richard Harrison
"I have no trouble receiving FM radio broadcasts on a small am/fm radio
I sometimes listen to while onboard commercial jet sirliners (flying at
cruise altitude), but I bever seem to be able to pick up AM radio
stations. It`s just static across the AM band.
Any explanation for this?"
Fuselage of the airliner acts as a waveguide below cutoff frequency
(where diameter is at least 1/2-wavelength). Below cutoff, attenuation
soars rapidly.
FM wavelength is about 3 meters. AM wavelength is about 300 meters.
Propagation of FM inside the fuselage is OK. Propagation of AM inside
the fuselage vanishes quickly.
You need to stick the suction cups of your Zenith portable`s Wave Magnet
to a window to get AM reception.
Best regards, Richard Harrison, KB5WZI
J.Hoekstra
that are smaller then the holes in the cage.
"Geoff Glave" <nos...@nospam.com> schreef in bericht
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
>
>
Bob Myers
"Some Guy" <So...@guy.com> wrote in message news:41BB8C6A...@guy.com...
> 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)
Bob Myers
"Charles Newman" <charles...@comcast.net.spammers.will.be.shot.on.sight>
wrote in message news:yqidnc_QoZS...@comcast.com...
> 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.
Dave Holford
> 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
Dave Holford
>
> 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
Dave Holford
> > 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.
>
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
Some Guy
>> 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
>
> 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?
Dave VanHorn
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.
Bob Myers
"Some Guy" <So...@guy.com> wrote in message news:41C0EA5C...@guy.com...
> 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.
TaxSrv
> 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.
Watson A.Name - "Watt Sun, the Dark Remover"
"Geoff Glave" <nos...@nospam.com> wrote in message
news:HxHud.9448$eb3.8331@clgrps13...
> > Any explanation for this?
>
> FM radio generally operates at longer range than AM radio,
Nonsense! AM radio stations can be heard for thousands of miles, FM for
'line of sight', which is usually less than a hundred miles.
> however it's
> limited to line-of-sight. However, when you're 40,000 feet up you can
> "see" a lot of transmitters hence the FM signals.
Nonsense! The passenger is sitting in a Faraday Cage, a fuslage made of
alumninum. The FM wavelength is short enough to go thru the windows,
but mot the AM signals.
Watson A.Name - "Watt Sun, the Dark Remover"
"Ian Jackson" <IanJacksonR...@g3ohx.demon.co.uk> wrote in
message news:QQZkixB8...@g3ohx.demon.co.uk...
> In message <HxHud.9448$eb3.8331@clgrps13>, Geoff Glave
> <nos...@nospam.com> writes
> >> 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.
> >
> >Geoff Glave
> >Vancouver, Canada
> >
> >
>
> 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.
Watson A.Name - "Watt Sun, the Dark Remover"
"Richard Clark" <kb7...@comcast.net> wrote in message
news:mf2nr0hn2u850gube...@4ax.com...
> On Sat, 11 Dec 2004 14:11:44 -0800, "Ed Price" <edp...@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
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.
Watson A.Name - "Watt Sun, the Dark Remover"
> 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.
Ed Price
"Watson A.Name - "Watt Sun, the Dark Remover"" <NOS...@dslextreme.com> wrote
in message news:10sogbl...@corp.supernews.com...
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
Ed Price
He's not dumber than "I" thought!
Ed
wb6wsn
Ed Price
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
Ed Price
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
Robert Baer
It is official; i just read in one of my electronigs mags i get that
the FAA indeed has ruled that airlines can allow use of computers over
the net when flying.
But it is up to each given airline to modify their own giudelines (as
they see fit).
Robert Baer
"Faraday shield" to some degree is a myth.
I have seen radars inside quonset huts track a *bird* flying a few
miles away (thru the metal wall)!
Ed Price
"Robert Baer" <rober...@earthlink.net> wrote in message
news:41CE87D3...@earthlink.net...
You must have some strange buddies. Who in the world would set up a radar
within a metal hut? And even if they did, who would think it's a good idea
to stay inside with it if it were on?
There's nothing mythical about the Faraday shield; it works really well, so
long as there are no discontinuities (apertures) and sufficient thickness
and conductivity. Under real-world conditions, steel works pretty good, and
any thickness sufficient to support itself will yield great shielding
effectiveness. So the only real performance variable left is the holes in
the conductive surface. How many, maximum dimension, proximity of radiating
source to the shield, etc.
While I would expect a Quonset hut to really mess up the accuracy of a
radar, it likely wouldn't be a good shield, as the floor isn't metal, I
don't think the ends are metal, and the various skin panels are rather
poorly RF bonded.
Ed
wb6wsn
Watson A.Name - "Watt Sun, the Dark Remover"
You use weasel words like 'to some degree' to avoid talking about the
truth. Radio waves don't go thru a sheet of metal.
> I have seen radars inside quonset huts track a *bird* flying a few
> miles away (thru the metal wall)!
No, not thru a metal wall. I saw the radar go thru the wooden walls of
the bldg when I was in radar repair school in the army. But that was
wood. Your so-called metal quonset hut was probably wood or fiberglass.
If you saw anything, it was probably your own reflection off the metal
walls, IF it didn't fry you like a porkchop in a microwave oven!
Robert Baer
I do not think your objections concerning the floor or the bonding of
the panels are too relevant.
The ends are metal and not relevant either.
The radar was pointing right at the wall (no windows nearby); any
presumed leakage via remote holes that you assumed might allow the
transmitted signal to leak, but would then not be focused on the bird(s)
and the path lengths would vary.
But the reflected signal from the bird or birds would be rather weak
and could not possibly be received via the same wild path(s) to a very
directional antenna.
My point is that a Farady shield is a good attenuator, but not
"perfect" as ASSuMEd.
And it sure is not "flat" in attenuation characteristic as a function
of frequency.
Robert Baer
Nope; it was a metal quonset hut; Army Signal Corps Fort Huachuca
AridZona.
Ed Price
Those weren't objections, they were speculations on my part as to how you
boys could have been finessing the generally applicable laws of physics.
But truly, the story stinks. So you and your army buddies are in this metal
hut, with a fairly high-power radar, and somebody comes up with the bright
idea to turn the thing on. Apparently no thought about RF personnel hazards
and no concern about strong reflections cooking your detector. Did you test
your M16's in a Quonset hut too?
Next point. "The radar was pointing right at the wall..." Now tell me, in a
semi-circular Quonset hut, how do you point anything "right at the wall"?
Maybe straight up?
Now, a bird doesn't have a very big radar cross section, maybe only about
0.01 square meters, so the return loss is really big. And to resolve a
single bird, I'm gonna guess that you had an X or K band radar. So let's run
some numbers. Let's say you had a 100kW radar, with a 30 dBi antenna of 1
square meter aperture. At 1500 meters, your detector power would be about 1
picowatt, or -60 dBm. Well hey, that's pretty decent, I'll bet you could see
a bird at one mile.
But that's assuming no loss at all due to the metal hut skin. Let's see what
happens if we say that the metal hut walls give us only 40 dB of shielding
(by absorption or reflection, it doesn't matter). That bites 80 dB out of
your path budget, putting your detector signal down to -140 dBm. I think
your story just ran out of luck.
Now you can argue about the 40 dB shielding effectiveness of the metal wall,
but I'll say that I was being very generous about that. At 10 GHz, I know
(How? Easy, I do it everyday. Just 3 days ago, I was keeping some 1.3 GHz
from radiating off of some cables, and it was common old Reynolds Wrap to
the rescue.), I can get >100 dB out of a sheet of aluminum foil. The SE is
so damn high from the material that the only significant factor is when the
energy finds a path around the shield.
Don't try to argue that a Faraday cage leaks; you appear to be trying to
build a general case based on your experience of always having observed
leaky structures. Sure, I know that shielding varies with lots of factors,
conductivity, permeability, thickness, frequency, angle of incidence,
distance from source, and then there's the problem of apertures. But your
hut, with plain old galvanized steel about 1/16" thick, would make a great
shielded enclosure, as long as the joints didn't leak.
BTW, I don't like using the term "Faraday cage". Despite all due respect to
Mr. Faraday, calling it a shielded enclosure is a clearer description.
Ed
wb6wsn
Richard Harrison
"So the only real performance variable left is the holes in the
conductive surface."
A plane window, like the fuselage itself, acts as apipe below cutoff
frequency. Minimum size for low attenuation is 1/2-wavelength.
The thicker the window frame, the longer the waveguide and the greater
the attenuation at frequencies below cutoff. See page 277 of
"Transmission Lines, Antennas, and Wave Guides" by King, Mimno, and Wing
to quantify the attenuation. It`s big below cutoff.
Best regards, Richard Harrison, KB5WZI
Robert Baer
I was not alluding to leakage; a more accurate term would be
re-radiation.
Take an ordinary transformer; it radiates a magnetic field, despite
the fact that the core is a closed loop.
In fact, one could get nasty and say the same thing about a toroid
transformer.
Now add a shorted copper turn around the outside of the ordinary
transformer's core (i have seen this on many TV power transformers and
others as well).
What happens? That magnetic field induces a current in that shorted
turn, making an opposing magnetic field - thereby reducing the net
radiated magnetic field greatly - but not to zero.
Now, instead of using that closely wrapped copper shoted turn, put
that transformer inside that shielded room you love.
Results: great reduction, but not to zero.
Increase the frequency to something one might consider RF.
Now one has an RF transmitter inside that shielded room, inducing
currents in the wall(s).
Those currents create opposing fields, and greatly attenuate the
signal outside the walls.
But they are not zero.
BW, radar is usually pulsed, and in the megawatt to multi-megawatt
region for the pulse.
Also, the quonset huts i saw had relatively vertical walls; the
rounded curvature was more so near the top.
And it might help to ask the bird(s); they even dislike those pesky
jets getting in their way.
Dave VanHorn
There may have been one slaved to it, inactive, inside the hut to
demonstrate what's going on upstairs.
There are plenty of good reasons why such a demo wouldn't work as described,
from killing the detector with strong reflections, to massive
re-re-reflections inside the building, to the fact that radar relies on a
"pencil" beam that wouldn't survive through those walls in any rational way,
and so on.
Ed Price
SNIP
My shielded enclosure only asks that I respect it; I don't think it would
provide better SE even if I told it that I loved it.
> Results: great reduction, but not to zero.
Nothing ever goes to zero; I'll usually settle for "great" reductions.
> Increase the frequency to something one might consider RF.
> Now one has an RF transmitter inside that shielded room, inducing
> currents in the wall(s).
> Those currents create opposing fields, and greatly attenuate the
> signal outside the walls.
You're getting a little fuzzy here. The propagating wave induces surface
currents on the metal barrier. The currents "sink" into the metal,
decreasing to about 37% (1/e) in what's called a "skin depth". At 10 GHz, a
"skin depth" in steel is really thin. After even 10 skin depths, the current
is down to only about 1/100,000 of what was on the surface. And there's a
whole lot of more skin depths to go before the current is presented to the
far surface of the steel barrier. And only then does the surface current on
the far side of the barrier get to launch a propagating wave.
Note that the "opposing fields" you mentioned are on the INSIDE, the near
surface, of the barrier. The reflected field is 180 degrees out of phase
with the incident field, so, real close to the metal surface, the E-field
nulls. OTOH, that reflected wave now goes marching back at you, creating
lots of fun with out-of-phase energy pumped back into the original radiating
element. Everybody sees bad, bad VSWR. And, since you guys were inside a
metal hut, there's even more fun in store for you. Not all that energy goes
back into the originating antenna. A lot of it just keeps bouncing around
inside the hut, creating 3-D variations in power density. Think of yourself
as a potato, slowly cooking.
So, to keep this straight, the current that survives Ohmic losses to make it
to the far side of the barrier doesn't "greatly attenuate the signal outside
the walls". It actually creates the signal (the propagating wave) on the far
side of the barrier.
We can talk about aperture leakage and re-radiation from barrier impedance
discontinuities some other time.
> But they are not zero.
> BW, radar is usually pulsed, and in the megawatt to multi-megawatt
> region for the pulse.
Multi-megawatt? Hmm, 10 MW? OK, and maybe a duty cycle of 0.01%? Isn't that
1 kW average? I own a 250 kW X-band radar that will do up to 0.1% duty
cycle. I sure wouldn't sit in a metal box with that thing running! I
wouldn't even want to be in the boresight of the antenna within a few
hundred feet. I was trying to be charitable in assuming that nobody would be
so dumb as to fire up a multi-megawatt radar INSIDE a metal hut. Looks like
you guys proved me wrong!
Ed
wb6wsn
Ed
wb6wsn
Julia Child
Who's posting these?
Ed Price wrote:
>
> oil.
> Add a little water, season, then add the carcass.
> Simmer for half an hour keeping the stock thick.
> Remove the carcass and add the vegetables slowly to the stock,
> so that it remains boiling the whole time.
> Cover the pot and simmer till vegetables are tender
> (2 hours approximately).
> Continue seasoning to taste.
> Before serving, add butter and pasta,
> serve piping with hot bread and butter.
Bob Miller
wrote:
ignore
>What's with all the recipe bullshit posts?
>
>Who's posting these?
Well, this is the info I received. I don't really understand it, but
this is what I was told:
Hello,
this message is never sent unsolicited. Don't panic.
You - or more precisely someone using your mail address - have
posted a test message to the following Newsgroups:
de.alt.test,bit.listserv.test,rec.radio.amateur.antenna
Your message was sent
Sat, 25 Dec 2004 21:01:30 GMT
travelling from your location to the news.karlvalentin.de (Germany).
Your article arrived here at Sun Dec 26 2004 00:40:05 +0100 (CET)
and this is the way it went (read from back to front):
news.karlvalentin.de!news.qymp.de!tarantoga!auth.de.news.easynet.net!spool3.bllon.news.easynet.net!easynet-quince!easynet.net!news.glorb.com!transit1.nntp.hccnet.nl!transit.nntp.hccnet.nl!transit2.nntp.hccnet.nl!feeder.news-service.com!psinet-eu-nl!news.satx.rr.com!149.52.149.150.mismatch
Reflector Mail is sent to anybody posting into a group ending with
the
word ".test". If you don't want to receive reflector mails, include
e.g.
the words 'ignore' at the top of your articles.
For obvious reasons, mails to refl...@karlvalentin.de are directed
into /dev/null. If you feel to write us, send your mail to
news...@karlvalentin.de instead.
Full headers plus the first 20 lines of your original message were:
| Path: news.karlvalentin.de!news.qymp.de!tarantoga!auth.de.news.easynet.net!spool3.bllon.news.easynet.net!easynet-quince!easynet.net!news.glorb.com!transit1.nntp.hccnet.nl!transit.nntp.hccnet.nl!transit2.nntp.hccnet.nl!feeder.news-service.com!psinet-eu-nl!news.satx.rr.com!149.52.149.150.mismatch
| From: Bob Miller <rmil...@satx.rr.com>
| Subject: Re: Modification of G5RV - need help on this
| Approved: Bob Miller <rmil...@satx.rr.com>
| Newsgroups: de.alt.test,bit.listserv.test,rec.radio.amateur.antenna
| References: <g97rs05mcn3ecvacr...@4ax.com>
| Date: Sat, 25 Dec 2004 21:01:30 GMT
| Message-ID: <3oxix0yd3b0a7g4uv...@4ax.com>
| X-Newsposter: AtomicPost/32 (http://149.52.149.150) Registered
| NNTP-Posting-Host: 149.52.149.150
| X-Trace: satx.rr.com 5830402087 149.52.149.150 (25 Dec 2004 21:01:30 GMT)
| Followup-To: news.admin.net-abuse.email
| Lines: 49
| Xref: news.karlvalentin.de de.alt.test:11560
|
| soften.
| In skillet, brown the meat in a little olive oil,
| then add onions, peppers, and celery (all chopped finely)
| and season well.
| Place in a large bowl and cool.
| Add seasoned breadcrumbs and a little of the tomato gravy,
| enough to make the mixture pliable.
| Divide the stuffing among the cabbage leaves then roll.
| Place seam down in a baking pan.
| Ladle tomato gravy on top,
| and bake at 325¦ for 30 - 45 minutes.
|
|
|
| Umbilical Cordon Bleu
|
| Nothing is so beautiful as the bond between mother and child,
| so why not consume it?
| Children or chicken breasts will work wonderfully also.
Miguel Cruz
> Julia Child <Iron...@cooks.r.us> wrote:
>> What's with all the recipe bullshit posts?
>>
>> Who's posting these?
>
> Well, this is the info I received. I don't really understand it, but
> this is what I was told:
>
> You - or more precisely someone using your mail address - have
> posted a test message to the following Newsgroups:
>
> de.alt.test,bit.listserv.test,rec.radio.amateur.antenna
That's just a side-effect of the message having been posted to a 'test'
newsgroup - basically irrelevant to the real issue.
Look up 'hipcrime' in google for more info about what went on with the baby
recipes.
miguel
--
Hit The Road! Photos from 32 countries on 5 continents: http://travel.u.nu
Richard Harrison
continuous sheets of metal in this thread. That`s generally wrong.
A Faraday screen, shield, or cage is a network of parallel wires or
strips connected together at one end but disconnected from each other at
their opposite ends. I`ve worked at several broadcast stations which
used Faraday screens at every tower to magnetically couple the tower to
the feedline while eliminating all capacitive coupling. The purpose is
to disadvantage harmonic coupling to the tower in which capacitance
favors due to lowered capacitive reactance at the harmonic frequencies.
At the stations, two coupled coils are used. They are close together and
share the same axis. Between the two coil forms is erected a heavy plate
sliced with parallel cuts. These start at one edge of the plate but end
before reaching quite to the other edge. The purpose is to eliminate
capacitive coupling between the coils but to allow tight magnetic
coupling between the coils. In the broadcast station they also have
another salutary effect. The tower`s lightning strikes nearly all are
terminated on the Faraday screen and kept out of the radio equipment.
A Faraday screen, shield, or cage is a network of parallel wires or
strips connected on one end but disconnected from each other at their
opposite ends. It`s similar to a conductive comb. The connected ends of
the wires are usually grounded.
The open-circuit wires prohibit circulating current from wire to wire.
Fields of the induced current would cancel the field of the inducing
current thus canceling inductive coupling. Due to the gaps, the screen
is transparent to the magnetic field but the wires capture the
electrostatic lines of force and eliminate capacitive coupling through
the screen.
A screen properly grounded at both ends of the wires sliminates magnstic
and electrostatic coupling. It is a shield but not a Faraday shield.
A continuous conducting shield is not a Faraday shield, even if
perforated with small holes. A lot of screened rooms have been
constructed from copper window screen. It decouples the contentents of
the room from the whole world when done correctly.
Ian White, G3SEK
>
>A Faraday screen, shield, or cage is a network of parallel wires or
>strips connected together at one end but disconnected from each other
>at their opposite ends. I`ve worked at several broadcast stations which
>used Faraday screens
The special comb-like structure that Richard describes, which is
deliberately constructed to block electric fields but transmit magnetic
fields, is normally called a Faraday "screen" - but not a cage.
The term Faraday "cage" is reserved for a complete conducting enclosure
that blocks both electric and magnetic fields from entering the
interior.
The rest of the discussion is about how well an incomplete or penetrated
enclosure might work as a Faraday cage.
--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek
Richard Harrison
"---but not a cage."
A cage according to my American dictionary is:
"A boxlike receptacle or enclosure for confining birds or other animals,
made with openwork of wires, bars, etc."
Ian sent me to my dictionary of electronics which reads:
"Faraday cage-See Faraday Shield"
Usage varies from place to place. I don`t know if I`m vindicated or
stand corrected.
Ian Jackson
Harrison <richard...@webtv.net> writes
Was it not an Ice Bucket which Faraday used to demonstrate the fact that
the electrostatic charges repelled each other as far as possible, and
therefore stayed on the outside of the bucket? The inside was
electrically dead.
Ian.
--
Richard Clark
<IanJacksonR...@g3ohx.demon.co.uk> wrote:
>Was it not an Ice Bucket which Faraday used to demonstrate the fact that
>the electrostatic charges repelled each other as far as possible, and
>therefore stayed on the outside of the bucket? The inside was
>electrically dead.
Hi Ian,
Maybe it was part of an office party. Anyway, Gauss demonstrated that
electric charge FIELD LINES prefer as much separation as possible
(which conforms to your charges being repelled). With a curvature,
the field line normal to the surface will either cause line crowding
or line spreading depending upon the geometry. With a positive
curvature (the outside of a conducting shell) the lines spread; with a
negative curvature (the inside of a conducting shell) the lines
converge. Given that the bucket is conductive inside and out, he
demonstrated that line proximity within the bucket drove the charges
outside. This is not quite an issue of charges being repelled as far
as possible, or they would be uniformly distributed inside and out.
By the same logic (and experience), charge will accumulate on the
surface at the smallest radius - hence the points on lightning rods.
By extension, this is also the source of capacitor failure at either
the edges (smallest radius of a plate) or in surface burrs.
HCJB, in Quito, suffered from corona discharge and converted to loops
(misnomer, actually box), they still suffered when the corners
(smallest radius) supported the same discharge (being corner fed).
They shifted to a center feed point and put the hi voltage nodes at
the middle of a wire span.
Ian Jackson
<kb7...@comcast.net> writes
>By the same logic (and experience), charge will accumulate on the
>surface at the smallest radius - hence the points on lightning rods.
>By extension, this is also the source of capacitor failure at either
>the edges (smallest radius of a plate) or in surface burrs.
>
Again scraping the very bottom of the memory banks, I seem to recall
that when lightning rods were first used (in the late 1700s), the
British used sharp points. The French, in the spirit of one-upmanship,
decided that theirs should have brass balls. DOH!!!
Ian.
--
Jack Painter
"Ian Jackson" <IanJa...@g3ohx.demon.co.uk> wrote
Very interesting! However the American Benjamin Franklin's pointed
lightning rods (it was not a British design) was never scientifically
challenged until a couple of years ago. Scientists have now shown that
blunt-tipped air terminals are attached by lightning with significantly
higher frequency than sharp tipped rods are. Pretty amazing that it took
over 230 years to "discover" this! So scrap the concept that a sharp edge
attracts charges, at least it does not attract lighting, the ultimate
charge.
http://www.usatoday.com/weather/resources/basics/2000-05-15-lightn-rod-tests.htm
http://www.esdjournal.com/articles/franklin/franklin.htm
http://www.mikeholt.com/news/archive/html/master/lightningblunt.htm
etc, etc
Jack Painter
Virginia Beach VA
J. Mc Laughlin
have required the ends to be converted to round from pointed when the
Revolution started - a pointed slam at Dr. Franklin. Nevertheless, the
houses (once there were two) of parliament were protected by Dr. Franklin's
rods.
It would have been so easy for the English to have co-opted Dr. Franklin
and quite changed the course of history. Instead, he conned the French out
of the critical support needed to win our freedom. 73 Mac N8TT
--
J. Mc Laughlin; Michigan U.S.A.
Home: J...@Power-Net.Net
Gary Schafer
wrote:
Jack,
All three references are of the same article. Note the rebuttals at
the end of one of them.
I would also find it hard to believe that ANY rods on a 12000 foot
mountain were not hit in 7 years!
That study would suggest that pointed rods were excellent lightning
repellers and would protect things from being struck. Exactly what
Franklin first thought.
If not excellent repellers then it would be highly suspect of the
placement of the pointed rods on the mountain.
73
Gary K4FMX
Richard Harrison
"I would find it hard to believe that ANY rods on a 12,000 foot mountain
were not hit in seven years."
I saw a PBS program tonight on people scaling the highest peak in
Antarctica. It may never have been struck by lightning in modern times.
I spent two six-month hitches for my company on Tierra del Fuego. Not
quite Antarctica, but still so cold that lightnning is unknown on the
island.
Ian Jackson
<j...@power-net.net> writes
<j...@power-net.net> writes
>There is more to the Franklin rods used in England: George III is said to
>have required the ends to be converted to round from pointed when the
>Revolution started - a pointed slam at Dr. Franklin. Nevertheless, the
>houses (once there were two) of parliament were protected by Dr. Franklin's
>rods.
>
> It would have been so easy for the English to have co-opted Dr. Franklin
>and quite changed the course of history. Instead, he conned the French out
>of the critical support needed to win our freedom. 73 Mac N8TT
>
>--
>J. Mc Laughlin; Michigan U.S.A.
>Home: J...@Power-Net.Net
>
>
'Protected' is the word. What is not always appreciated is that the
primary purpose of lightning rods (usually called 'lightning conductors'
in the UK) is to PREVENT a strike by allowing the electrical charge to
leak away before sufficient voltage builds up to cause an actual strike.
Ian.
--
Ian White, G3SEK
Me neither! The main lesson is that we have to be careful to define what
we mean, because there's a strong risk that other people might
understand something different.
Faraday cages are used at CERN and other large particle accelerators, to
keep the sensitive particle detectors isolated from the pulsed megawatts
of RF energy that are kicking the particles around the ring. CERN is an
international facility, so each country has its own experiments using
separate Faraday cages.
Several years ago, I needed to call a friend who was working at CERN.
Someone picked up the phone, and a voice said "British Cage".
"Well," I thought, "that certainly puts us in our place..."
Ed Price
"Julia Child" <Iron...@cooks.r.us> wrote in message
news:41D16E75...@cooks.r.us...
> What's with all the recipe bullshit posts?
>
> Who's posting these?
>
> Ed Price wrote:
>>
SNIP
No, I didn't write that. However, "Julia", rest assured that, by posting
your question, your address will soon be harvested for use by the Hipcrime
bot in the DOS attack. Don't reply, don't post about it, don't help the bot.
Ed
wb6wsn
Jack Painter
"Gary Schafer" <gasc...@comcast.net> wrote
> Jack,
>
> All three references are of the same article. Note the rebuttals at
> the end of one of them.
>
> I would also find it hard to believe that ANY rods on a 12000 foot
> mountain were not hit in 7 years!
>
> That study would suggest that pointed rods were excellent lightning
> repellers and would protect things from being struck. Exactly what
> Franklin first thought.
>
> If not excellent repellers then it would be highly suspect of the
> placement of the pointed rods on the mountain.
>
> 73
> Gary K4FMX
Hi Gary, the study is of course much more detailed than the articles
describe, I'll see if I can find you a link or post the abstract here
anyway. But no, there is absolutely no such conclusion in that study (or any
other accepted work) that any device can prevent lightning from striking a
particular point by "draining off" charges.
73,
Jack
Jack Painter
"Ian Jackson" <IanJacksonR...@g3ohx.demon.co.uk> wrote
> 'Protected' is the word. What is not always appreciated is that the
> primary purpose of lightning rods (usually called 'lightning conductors'
> in the UK) is to PREVENT a strike by allowing the electrical charge to
> leak away before sufficient voltage builds up to cause an actual strike.
> Ian.
Hi Ian, while Franklin originally thought this was the case, he and others
soon realized that safe handling of a lightning attachment was the function
of his Franklin Rods, NOT avoidance of attachment. There has never been any
proof that any device can prevent a strike from attaching to a particular
point. The controversy surrounding the CTS (Charge Transfer System) and ESE
(Early Streamer Emitters) exposes some of the dumbest junk science ever to
hit the lightning-rod snake-oil trail. It has been thoroughly discredited as
having absolutely zero effectiveness as a preventer and limited usefulness
as a standard Franklin Rod when installed as its snake-oil purveyors
proscribe. So please never assume that any rod, termination device,
voodoo-doll on the roof or anything else can have any affect whatsoever of
preventing a strike from attaching at any particular point.
Jack Painter
Virginia Beach, Virginia
Ian Jackson
<223...@cox.net> writes
As I said, I WAS scraping the very bottoms of the memory banks (and
licking them clean as well).....
Ian.
--
Reg Edwards
middle of thunderstorms? And he now gets praised for it!
Joel Kolstad
>> news:mf2nr0hn2u850gube...@4ax.com...
>>> On Sat, 11 Dec 2004 14:11:44 -0800, "Ed Price" <edp...@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.
Why is an AM/FM radio receiver potentially more dangerous than laptop PCs,
gameboys, DVD players, and other electronic devices that are used quite
routinely on airplanes?
Joel Kolstad
> "Faraday shield" to some degree is a myth.
I'd say it's more a case of people tending to think that various metal
structures such as cars, airplnes, metal boxes, etc. are close to ideal
'Faraday shields' when, in actuality, they might only be a poor
approximation. (It's this line of reasoning that usually flummuxes people
when they try to shield a monitor that has a wavvy display from some
extneral field with a steel box and find it's not very effective.)
> I have seen radars inside quonset huts track a *bird* flying a few
> miles away (thru the metal wall)!
Hmm... any idea if the folks inside weren't being exposed to far more
radiation that what we'd typically consider safe? :-)
---Joel Kolstad
Joel Kolstad
news:_mdAd.14884$8e5.14258@fed1read07...
> I was trying to be charitable in assuming that nobody would be so dumb as
> to fire up a multi-megawatt radar INSIDE a metal hut. Looks like you guys
> proved me wrong!
There's a Simpsons episode where Homer and Marge check out the house for
sale next door, and find that it has a very high end, contemporary kitchen
including a microwave oven big enough to walk in... something that Homer
immediately does, of course.
Jack Painter
"Reg Edwards" <g4fgq...@ZZZbtinternet.com> wrote
> Wasn't Franklin that lunatic who used to walk around flying kites in the
> middle of thunderstorms? And he now gets praised for it!
That was an experiment thousands of schoolteachers must dread, or rather
that it actually made the schoolbooks and includes artist renderings, in
case enterprising young minds wish to recreate this "experiment".
Frightening thought how many may have actually tried it, eh? ;-)
73,
Jack
Va Bch