Ultralight DX on an Airplane?


Andres Perez
 

This is a very old thread, looking for new information... But in the meantime, I have a story to tell...

As part of my job, I have to travel a lot in the US/Canada but also LACA and sometimes everywhere else...  recently I took an Air Canada flight from Toronto to Bogota, Colombia and I sat down next to a fellow who was listening to FM in the plane using an Android phone. This was so interesting, I pulled out my own mobile device and started listening to FM radio too. I got to listen to a few radio stations from Florida, Dominican Republic, Jamaica, and Colombia as I flew over those countries. I was immediately hooked in this new hobby!

I purchased a Sony ICF-P26 at Walmart (very cheap radio) and on a recent trip from Los Angeles to Toronto, I listened to FM stations from Colorado, Iowa, Illinois.... interestingly enough I was not able to tune into any AM stations.

One of the problems, as many people have said above, is that you lose the station very quickly. But last weekend I flew from YYZ to IND and listened to NPR (https://www.npr.org/) from Erie, PA as soon as the plane took off from YYZ. The program they were broadcasting (https://www.npr.org/programs/weekend-edition-sunday/) was pretty interesting but I lost the signal very soon. Fortunately, I was able to pick up another NPR station from Cleveland, OH and continue listening to the same show. When I lost Cleveland, OH I picked up another NPR station from Columbus, OH, then Cincinnati, OH then Indianapolis, IN... I was able to listen to the whole program because different NPR stations were broadcasting the same program.

If I can tune to these stations with a cheap radio, I wonder what I could do with a nice one!

The first thing I would like to know is if you have heard about this before (listening to the radio on a plane)... Is this legal? I know they ask us to turn off mobile devices and electronic devices because they can generate interference... but a small radio that you can only receive a signal, should not interfere with the airplane... The only thing that I am doing is capturing the radio waves that are already reaching the plane.

I would also appreciate if anybody can suggest a good radio to use on my flights.

Thanks 


policow6@...
 

I would expect AM signals to be blocked by the metal surrounding on a plane just as it is in a car. You may remember the old Zenith ads where they showed people on airplanes using the removable Wavemagnet antenna suction-cupped to a window.


Jay


Tony King <dx4me2@...>
 

If a pocket size cassette/ radio can be counted as Ultralight - I logged and verified a Greenland AM station en route with KLM from London to Los Angeles in the 80's.

Tony


Michael <michael.setaazul@...>
 

On my old SONY, I used to listen to FM and shortwave on my commute
by rail. The same FM programmes were broadcast from different
transmitters, so it was possible to follow a programme
as the train progressed. I clipped a short wire antenna
to the curtain rail with the wire hanging down the window
for shortwave.

Any AM/FM superhet radio transmits a very weak signal from
the local oscillator, so for the avoidance of doubt concerning
possible interference to aircraft electronics, radios were
not allowed in flight. There might also have been a concern that a
modified radio could be used in flight to sabotage avionics.
Any such fears seem to have been revised now that laptops and
even cellphones are allowed during flight. I assume either avionics
are now more resiliant or it has been determined that the risk of interference is negligible.

Michael UK

On 13.09.18 04:18, andresperezf@... [ultralightdx] wrote:

...
I purchased a Sony ICF-P26 at Walmart (very cheap radio) and on a recent trip from Los Angeles to Toronto, I listened to FM stations from Colorado, Iowa, Illinois.... interestingly enough I was not able to tune into any AM stations.
One of the problems, as many people have said above, is that you lose the station very quickly. But last weekend I flew from YYZ to IND and listened to NPR
...


Andres Perez
 

Thanks for your replies.

@jay.policow, I that would make sense and would explain why I can't listen to AM inside the plane. When trying to tune to any radio station in the plane, I just hear very loud high peach tones. Will the same happen on other bands like SW? or the Airbands? (VHF).

One more question... Is it possible with a portable Airband radio to listen to communications from the pilots of my plane? I have heard this could damage the radio because I am very close to the antenna that transmits the signals.


Andy
 

andresperezf wrote:

    "... a small radio that you can only receive a signal, should not interfere with the airplane... The only thing that I am doing is capturing the radio waves that are already reaching the plane."

That's where you are somewhat wrong.  Since almost 100 years ago, most radios are Edwin Armstrong's "superhet" design where there is a local oscillator that "beats" with the incoming signal and shifts it to a new frequency, the "IF" frequency.

Therefore, they do not only passively receive signals.  They also generate small amounts of RF, some of which inevitably gets out of the box and radiated.  Yes, it's small, and it's entirely undesirable.  But it's there.  Even if they use a shielded metal box (it comes out through the antenna terminals).  It can be measured, and it could interfere with sensitive receivers nearby that are trying to receive a frequency near to your local oscillator, or a harmonic of it, or a product of the "mixer" that combines the LO signal with the incoming RF.

This is why they've been "banning" the use of all electronic devices aboard commercial airplanes.  There is the possibility, however slight, of your AM or FM radio, radiating a small signal that interferes with the plane's communications or navigation equipment.

In truth, I think the fear was probably way out of proportion with the reality.  But you can't really control what crappy radios consumers buy.  To make sure that a poorly designed transistor radio doesn't interfere, they had to ban all radios when the plane was in flight.

I know an engineer and pilot who did -- and published for the FAA -- a bunch of research several years ago, that proved that the risk was so negligible then to be virtually nonexistent.  That was two decades ago, and since then, most radio navigation has moved up to much higher frequencies where that particular problem pretty much doesn't exist as it once may have.  So I think the likelihood of there being a problem from a transistor radio, is even less than it was in the 1990s.

I have not flown on commercial aircraft in a few years.  But my recollection was that they still had you turn off all electronics during take-off and landing -- times when it's more critical and they want to make absolutely sure that nothing goes wrong.  Are they still doing this?  I don't know.

You can design radio receivers without the local oscillator.  They were known as "tuned RF" (or TRF for short).

Modern radio architectures such as SDR, which digitize the incoming RF waveform, are not immune because they use an oscillator to drive the sampling and digitization circuits that make the SDR work.  The mere presence of an oscillator, makes it capable of radiating RF, and it will.  It's only a matter of (a) what frequencies, and (b) how weak is the radiated signal.  It's never zero.

Regards,
Andy



kevin asato <kc6pob@...>
 

it's possible to receive airband radio inflight but i would not. you may actually interfere with the aircraft's capability of receiving necessary communications; not something i want anyone to do when i am flying onboard that particular aircraft. modern aircraft radios are probably more tolerant but why risk it?

as far as your radio is concerned, the radio should not be damaged by the aircraft transmitter. but that is not what i care about.
73,
kevin
kc6pob

One more
question... Is it possible with a portable Airband radio to
listen to communications from the pilots of my plane? I have
heard this could damage the radio because I am very close to
the antenna that transmits the signals.


kevin asato <kc6pob@...>
 

Hi Andy,
you can use small electronics during take off and landings. With the exception of WiFi on the planes, most airlines have the In Flight Entertainment (IFE) running gate to gate. Electronics larger than a tablet (computer) are to be stowed on take off and landing as they can become lethal projectiles or interfere with aircraft evacuation. it's already bad enough that there is hardly any room to use your laptop while seated normally on the plane.

Times have changed and electronics has advanced. Still i would not want someone to interfere with VHF voice communications which still relies on AM technology. It's bad enough that i have to get on a plane up to 50 times a year.
73,
kevin
kc6pob



I
have not flown on commercial aircraft in a few years.  But
my recollection was that they still had you turn off all
electronics during take-off and landing -- times when
it's more critical and they want to make absolutely sure
that nothing goes wrong.  Are they still doing this?  I
don't know.


Andres Perez
 

Thanks, guys.

One last question... Does listening to the pilots with a receiver, which is not able to transmit, cause any interruption in their communication? If so, I am the first person to stop using listening to them because my life is in danger.

I would understand if the radio was able to transmit, I would not want the pilots to hear noises from the cabin rather than the actual instructions from the tower.


Phillips
 

Superhet radio receivers are those that have a local oscillator and can emit a radio signal.  


A quick course in basic superhet theory.

There are two main frequencies at play in a superhet - the tuned frequency and the local oscillator frequency.   The local oscillator is normally set to a frequency above the tuned frequency and the two frequencies "track" each other as the radio is tuned to maintain a constant "difference" frequency.   This difference frequency is called the Intermediate Frequency (IF).   As it is a constant frequency, simple circuit techniques can be used to provide the massive amplification needed.


The local oscillator signal is small and does not contain any modulation and so will not carry any sounds from inside the aircraft.  At worst it will generate a fixed tone in the pilots' headsets.  And then only if a specific (and highly unlikely) arithmetic relationship exists between the aircraft receive frequency and the superhet's receive frequency.  This arithmetic relationship is equal to the IF of the superhet.


About the only time a superhet will generate a tone is when the superhet is tuned to a specific frequency some hundreds of KHz away from the aircraft receive frequency.  If the superhet is tuned to the same frequency as the aircraft, no tones will be generated. 


If the local oscillator is operating outside the aircraft radio's tuning selectivity,  the aircraft tuning circuitry will reject it and so any interfering radio would, not only need to be tuned within a small band of specific frequencies, but be in a location where its miniscule power could enter the aircraft radio circuitry.   


In the days of valve (tube) radios, the local oscillator could make power in the tens to hundreds of milliwatts and be detected over distances of twenty metres (sometimes more).   My first (and highly illegal) transmitter was a modified valve local oscillator circuit connected to an antenna.  It transmitted from the barracks to the car park.  These days, transistor local oscillators make very little power.


When flying in commercial aircraft, you can be assured that the aircraft is totally secure from locally generated interference.  



Here is an experiment if anyone is interested;


Tune one of your sensitive receivers to a vacant frequency above the middle of the AM band.  Turn the volume high.


Get a superhet radio and position it close to the sensitive receiver.  It must be a superhet - look for a group of little square cans on the circuit board.  A cheap one is best because it won't have any screening.


Tune it about 455KHz below the frequency of the sensitive radio. 


Slowly tune the superhet up and down and listen for a whistle or a damping of the static in the sensitive receiver. 


Once (if) you establish a whistle or static damping, move the domestic radio away.  You will find that it is not long before any signs of the local oscillator vanish.   Now you know how far that superhet's local oscillator will transmit - it won't be far.




Ray

 



 



From: ultralightdx@... on behalf of andresperezf@... [ultralightdx]
Sent: Tuesday, 18 September 2018 12:14 AM
To: ultralightdx@...
Subject: [ultralightdx] Re: Ultralight DX on an Airplane?
 
 

Thanks, guys.


One last question... Does listening to the pilots with a receiver, which is not able to transmit, cause any interruption in their communication? If so, I am the first person to stop using listening to them because my life is in danger.

I would understand if the radio was able to transmit, I would not want the pilots to hear noises from the cabin rather than the actual instructions from the tower.


Michael <michael.setaazul@...>
 

My understanding was that the original concern was that an oscillator
emitting inside the cabin *might* disrupt pre-digital avionics
- not crew communications. With advances in electronics, this has
been superseded by other concerns.

Michael UK
............................

On 18.09.18 01:52, ray Phillips phillicom@... [ultralightdx] wrote:
...
Superhet radio receivers are those that have a local oscillator and can emit a radio signal.
...
The local oscillator signal is small and does not contain any modulation and so will not carry any sounds from inside the aircraft. At worst it will generate a fixed tone in the pilots' headsets.
...
When flying in commercial aircraft, you can be assured that the aircraft is totally secure from locally generated interference.
Ray


Rémy Friess
 

You can even use superhets to decode SSB transmissions with a receiver that does not have SSB. You tune one set to the wanted frequency and the other 455 kHz below (provided it is single conversion) then you can use the tuning button as a clarifier (BFO).



De : ray Phillips phillicom@... [ultralightdx]
À : ultralightdx@...
Sujet : Re: [ultralightdx] Re: Ultralight DX on an Airplane?
Date : 18/09/2018 02:52:16 CEST

 

Superhet radio receivers are those that have a local oscillator and can emit a radio signal.  


A quick course in basic superhet theory.

There are two main frequencies at play in a superhet - the tuned frequency and the local oscillator frequency.   The local oscillator is normally set to a frequency above the tuned frequency and the two frequencies "track" each other as the radio is tuned to maintain a constant "difference" frequency.   This difference frequency is called the Intermediate Frequency (IF).   As it is a constant frequency, simple circuit techniques can be used to provide the massive amplification needed.


The local oscillator signal is small and does not contain any modulation and so will not carry any sounds from inside the aircraft.  At worst it will generate a fixed tone in the pilots' headsets.  And then only if a specific (and highly unlikely) arithmetic relationship exists between the aircraft receive frequency and the superhet's receive frequency.  This arithmetic relationship is equal to the IF of the superhet.


About the only time a superhet will generate a tone is when the superhet is tuned to a specific frequency some hundreds of KHz away from the aircraft receive frequency.  If the superhet is tuned to the same frequency as the aircraft, no tones will be generated. 


If the local oscillator is operating outside the aircraft radio's tuning selectivity,  the aircraft tuning circuitry will reject it and so any interfering radio would, not only need to be tuned within a small band of specific frequencies, but be in a location where its miniscule power could enter the aircraft radio circuitry.   


In the days of valve (tube) radios, the local oscillator could make power in the tens to hundreds of milliwatts and be detected over distances of twenty metres (sometimes more).   My first (and highly illegal) transmitter was a modified valve local oscillator circuit connected to an antenna.  It transmitted from the barracks to the car park.  These days, transistor local oscillators make very little power.


When flying in commercial aircraft, you can be assured that the aircraft is totally secure from locally generated interference.  



Here is an experiment if anyone is interested;


Tune one of your sensitive receivers to a vacant frequency above the middle of the AM band.  Turn the volume high.


Get a superhet radio and position it close to the sensitive receiver.  It must be a superhet - look for a group of little square cans on the circuit board.  A cheap one is best because it won't have any screening.


Tune it about 455KHz below the frequency of the sensitive radio. 


Slowly tune the superhet up and down and listen for a whistle or a damping of the static in the sensitive receiver. 


Once (if) you establish a whistle or static damping, move the domestic radio away.  You will find that it is not long before any signs of the local oscillator vanish.   Now you know how far that superhet's local oscillator will transmit - it won't be far.




Ray

 



 



From: ultralightdx@... on behalf of andresperezf@... [ultralightdx]
Sent: Tuesday, 18 September 2018 12:14 AM
To: ultralightdx@...
Subject: [ultralightdx] Re: Ultralight DX on an Airplane?
 
 

Thanks, guys.


One last question... Does listening to the pilots with a receiver, which is not able to transmit, cause any interruption in their communication? If so, I am the first person to stop using listening to them because my life is in danger.

I would understand if the radio was able to transmit, I would not want the pilots to hear noises from the cabin rather than the actual instructions from the tower.


Phillips
 

Pilots can request retransmissions to ensure understanding.  Besides, pilots are uncanny in their ability to understand voice communications over aircraft radio circuits despite all sorts of interference and distractions.


I spent years working avionics and there is very little that could be affected by a local oscillator.   All I can think of is maybe an AM direction finder.  Aircraft still use LW beacons for airport-status but any receiver tuned to air-ground-air comms would be so far up the spectrum that its local oscillator would be orders of magnitude away from the LW frequency.   As local oscillators are set to frequencies above received frequencies, it is highly unlikely that even a LW local oscillator could get down to a LW beacon.  


Mobile (cell) phones can transmit up to five watts even when not actually making a call.  As would tablets and other SIM-card-equipped  devices.  And they transmit that high power using digital encoding.  I am sure that the 20+Kms of wiring in a modern commercial aircraft would ingest a lot of that power.  How many people turn their phones completely off when in an aircraft?   I'd worry a lot more about digital 5W phones inside a digital aircraft than analogue microwatt superhets.


There are WiFi equipped devices which transmit digital signals in the 2.4GHz or 5.8GHz bands.  They produce only small amounts of power but it is deliberately radiated.   How much of that power is picked up by the aircraft?


Then there are external sources of interference.  Two fly-by-wire Airbus aircraft in the same area over the Indian Ocean to the North West of Australia, have suffered sudden loss of control followed by equally sudden restoration of control.  Someone using their phone......or transmissions from the super-high-power HAARP installation on the West Australian coastline almost directly under the flight path?    Maybe something else.    Fortunately no one suffered serious injury and there have been no recurrences since the two incidents.  Perhaps someone changed procedures or maybe the aircraft have been "hardened".


Eventually it all boils down to how well aircraft are engineered to be impervious to extraneous electronic insult and they are very well engineered indeed.  I don't fly myself (no need to) but I let my wife fly without any qualms, even on the "HAARP route".
 
Ray



From: ultralightdx@... on behalf of Michael michael.setaazul@... [ultralightdx]
Sent: Tuesday, 18 September 2018 3:55 PM
To: ultralightdx@...
Subject: Re: [ultralightdx] Re: Ultralight DX on an Airplane?
 
My understanding was that the original concern was that an oscillator
emitting inside the cabin *might* disrupt pre-digital avionics
- not crew communications. With advances in electronics, this has
been superseded by other concerns.

Michael UK
.............................

On 18.09.18 01:52, ray Phillips phillicom@... [ultralightdx] wrote:
....
> Superhet radio receivers are those that have a local oscillator and can
> emit a radio signal.
....
> The local oscillator signal is small and does not contain any modulation
> and so will not carry any sounds from inside the aircraft.  At worst it
> will generate a fixed tone in the pilots' headsets.
....
> When flying in commercial aircraft, you can be assured that the aircraft
> is totally secure from locally generated interference.
> Ray


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