Pilots: Scanner Interference Question

[Gilligan]

This question would probably best be answered by a pilot or airplane electronics tech. I've always wanted to listen to the pilots on board planes I was on but I knew that it was against aircraft rules. I've often had the scanner turned on while the plane was on the ground but never had the guts to leave it on in the air -- just in case. Just in case it actually does cause some kind of interference. If I actually turn it on while it's airborne, or if I just leave it tuned to one frequency (not scanning), what are the chances of me actually causing a problem? Don't people secretly use cellphones on planes all the time in the bathrooms and stuff? And what about the airphones? Outside of FAA restrictions and such, what is the truth about this?

 

[Colin9690]

Chances are nothing bad will happen. The reason why they tell you to turn off cell phones, etc is because they transmit RF energy. Things that transmit can mess with the GPS, compass equipment, and other navigation equipment. I doubt a scanner will disrupt anything though.

 

[CrewRest]

Fly United. They are the only airline to provide cocpit communications on the aircraft audio entertainment system

Doug Anderson
KG4QCR

 

[Luis_C]

Chances are nothing bad will happen. The reason why they tell you to turn off cell phones, etc is because they transmit RF energy. Things that transmit can mess with the GPS, compass equipment, and other navigation equipment. I doubt a scanner will disrupt anything though.

Yes, well, I think that now in the aeroplanes you could use your cell phone without causing any interference, because all the stuff is prepared for support interference, but maybe they just say no, because there's a change that a cable that has isolation, could lose the isolation or something, as it gets older or when it came new, so always there's a remotely chance to have interference in the cockpit, and they want to avoid risks, so RF stuff is forbidden.

Well, but to the guys who wonder, why they don't let receivers on board, is that some cheapo ones even if they are receivers, they cause interference, I was listening to my radio scanner, to airband, and there was a cheap radio clock on tuned in a FM station, and in one of the frequencies that I was listening to, there's intermod of that radio station, it was about 10 feet from me, and when they were talking into that frequency, I would hear the airplanes and that FM at the same time, and when I had the squelch at min, the intermodulation was much more strong than the normal, and reduced sensivility. I just mention it as an example of what can happen.

But well, scanners won't do this trouble, for sure but they don't know, and also I have this conspiration theory, that they don't want you to hear to the airband communications, when you are onboard, because sometimes there's some minor trouble, that might panic the passengers onboard. But there's United with aircraft communications in the entertainment system, as another member mentioned, so it might not be the case really.

I remember a movie, that an aeroplane has an emergency, but they just don't mention it to the passengers, and a passenger got a receiver for airband, and that he notices the stuff, and that he starts to get afraid and stuff, that the passengers get to know what's going on and the situation gets worse.

Hope you understand my points,

Luis

 

[blueline_308]

One of the reason that cell phones were banned in planes (way before 9/11 ) was that at 30,000 feet or so AGL, you will be hitting multiple cell towers, and at the speed the plane is traveling, would certainly cause havoc with the cell systems handing off the calls. This was in the analog days of cell phones, so maybe things have changed and I am sure that the technology to handle handoffs are much better, but the fact that your cell signal has a larger than desired footprint is still a fact. The older analog handheld phones used a stronger TX signal than do todays phones.

 

[N_Jay]

One of the reason that cell phones were banned in planes (way before 9/11 ) was that at 30,000 feet or so AGL, you will be hitting multiple cell towers, and at the speed the plane is traveling, would certainly cause havoc with the cell systems handing off the calls. This was in the analog days of cell phones, so maybe things have changed and I am sure that the technology to handle handoffs are much better, but the fact that your cell signal has a larger than desired footprint is still a fact. The older analog handheld phones used a stronger TX signal than do todays phones.

Cellular service was illegal from aircraft (by FCC not FAA rules) since its inception.

Yes, interference was a concern even before the systems were implemented, and it still is.

 

[CLB]

From personal experience from the right seat of a non GPS equipped Cutlass RG, my cellphone apparently threw off the ADF a little until I turned it off.

We were flying IFR @ or ~8000, so I should have remembered to turn it off before we departed. Who knows, It was an old plane in desparate need of an overhaul (avionics etc...but still airworthy). Perhaps the shielding on the equipment had somewhat declined.

 

[N_Jay]

From personal experience from the right seat of a non GPS equipped Cutlass RG, my cellphone apparently threw off the ADF a little until I turned it off.

We were flying IFR @ or ~8000, so I should have remembered to turn it off before we departed. Who knows, It was an old plane in desparate need of an overhaul (avionics etc...but still airworthy). Perhaps the shielding on the equipment had somewhat declined.

DUDE, you avionics are sensitive AM receivers, interference reception is what they do best.

The only way to "shield" them is to disconnect the antenna.

 

[gcgrotz]

On the topic of cellphones in planes: I don't know about GSM or Nextel - I suspect they have similar problems to the old analog systems as they use different RF channels and handoff etc. CDMA on the other hand, will not work in a plane. This is because all the sites in a system are on the same RF freq (or 3 or 4 on a busy system) and your call does what is called a soft handoff where you frequently are being carried by 2 or more cells at the same time. Being high in the air (even on small mountaintops here in VA) causes what is known as Pilot Pollution and the phone is unable to lock on a signal due to the multiple signals arriving at vastly different times creating digital garbage.

Even in the analog days you were lucky to get a call made above a few thousand feet due to the handoff issue and multiple control channels hitting your phone.

Now, when airlines start putting repeaters on planes and charging you 6.95 a minute to talk, then that is a whole different story and I wouldn't want to be on that plane!

 

[kb2vxa]

Hi all,

Let's get it straight from a historical perspective. The rule is as old as dirt, that is from back in the days when Fred and Wilma flew off to Hawaii or wherever that pteredactyl was off to. With all the improvements in aeronautics there is little that can disrupt them but then too with all this crappy consumer electronic junk around my guess is they just don't want to take any chances.

There's a lot more operating behind the scenes than your uninformed speculation can answer so why bother with all the blather? I'm no expert either which is why I just would rather do as I'm told while keeping "better safe than sorry" firmly in mind.

Hey, this radio is neat, turn the knob and the plane turns left, turn the other way and it turns right. This button makes it go up and this one... HEY, that was FUN! Call me Peter Pan, I'M FLYING! There goes the stewardess telling us there's nothing to worry about, she funny. WHEEEE!!!

"...and I wouldn't want to be on that plane!"
WHEEEHEHEHEEE!!!

"Now ain't I a stinkah?"
Bugs Bunny

 

[N_Jay]

Reminds me of a joke/comic I saw once (and can't find).

Why WiFi is not allowed on planes.

It shows a guy with a laptop on a plane with a Plug-and-play pop-up saying:

"Found new hardware;
"Boeing 757 control system: Instaling"

"Your new hardward is installed and ready for use"
:lol: :lol: :lol:

 

[Luis_C]

Hi all,

Let's get it straight from a historical perspective. The rule is as old as dirt, that is from back in the days when Fred and Wilma flew off to Hawaii or wherever that pteredactyl was off to. With all the improvements in aeronautics there is little that can disrupt them but then too with all this crappy consumer electronic junk around my guess is they just don't want to take any chances.

That's what I meant exacly, but in less words.

Reminds me of a joke/comic I saw once (and can't find).

Why WiFi is not allowed on planes.

It shows a guy with a laptop on a plane with a Plug-and-play pop-up saying:

"Found new hardware;
"Boeing 757 control system: Instaling"

"Your new hardward is installed and ready for use"
:lol: :lol: :lol:

Haha, really nice one.

 

[Audiodave1]

I'm not really qualified to answer the question wheather it "could" interfere or not but do a search for the Mythbusters TV series where they did their own research on the subject. (it'll air again)

Not that they are the most credible source but they generally make sense and make me laugh.

They could not cause a problem on a particular type of business jet with transmitters which likely have some of the same IF circuitry found in any receiver.

Dave

 

[Yokoshibu]

In regards to mythbusters:
you dont test that theory on a bussiness jet that was made in 2004... Test it on an older DC-9 that airtran flys or a 737-200 that southwest has... you will get different results... the thing everyone forgets is there are multiple freq's for vortacs and ILS/GS systems... to test the theory you would have to flip through every channelset being used in the us... it would really take a day or two just to try them all. Also RF can get into lines simple stuff like DC or AC lines and affect whatever it is powering... not a typical problem with low power but still enough to cause concern to some items... they dont put ferite beads on all of the electrical lines on an aircraft cause it doesnt make sense so they are imune to rf.

I run some stuff from home that affects my cable tv and I said to a friend that freq messes with my cable at home and he said let me try and see if I get the same result (I didnt tell him what TV channel or freq I was txing on) He told me I was smoking crack... I told him to go home and try channel XX and freq XXXX.XXX and sure enough he shot me an email that night... you were right.... its a matter of finding the 1 in 1000 chance you will screw something up somewhere ... and I dont feel like looking when I am in a tin can going 420 kts at 30000 feet in the air!

 

[DPD1]

That's all very true... The plane they "tested" was about as bullet proof as you can get. An older plane or larger airliner with more cable would have been more appropriate. I've actually had scanners emit enough energy while they're scanning, to lock up other scanners. So the RF can be there, albeit, very low. I think it could be possible in very remote cases to disrupt something with a scanner... But highly unlikely. When it's the airlines neck on the line though, that's all it takes to say no. They're not going to risk even the slightest chance, and that's probably a good thing.

Dave
http://www.dpdproductions.com
- Custom Scanner, Aviation, MURS, GMRS, Marine & Ham Antennas -

 

[Luis_C]

That's all very true... The plane they "tested" was about as bullet proof as you can get. An older plane or larger airliner with more cable would have been more appropriate. I've actually had scanners emit enough energy while they're scanning, to lock up other scanners. So the RF can be there, albeit, very low. I think it could be possible in very remote cases to disrupt something with a scanner... But highly unlikely. When it's the airlines neck on the line though, that's all it takes to say no. They're not going to risk even the slightest chance, and that's probably a good thing.

Yes, it's hardly difficult, but still possible, and because they really care about us, they do it, and that's good indeed.

 

[Gilligan]

I appreciate everyone's input to my question and wanted to see if anyone had any sure-fire answers about it. I think everyone is in agreeance that even if the chance is fairly small that a scanner would cause interference, it's just not worth the risk. Thanks for your answers.

 

[NAVCAN]

I work in the air-nav field, allbeit on the ground side, where we maintain all VOR's/ILS's/GS's DME's and Radars. When I saw that episode of mythbusters where they were checking out interference on that ADF, they got a huge deflection when they turned the Tx on. Later on, they mentionned that all the cables used were "un-sheilded".

So, as some of you were saying, the fact that an old 737-200 with old coax cables, and old ILS/VOR Rx antenna's, where the shielding could be damaged, could very well affect an OLD ADF.

When it comes to installing our new ILS systems, we use DGPS as a reference for a special ILS/VOR/DME/GS aircraft to verify the proper alignment of the ILS(Localiser and Glideslope). At the same time, we use 20W VHF Transponders & CDMA cellphones WHILE inspecting the approach. Since CDMA here in Canada is 800MHz (im not sure if it's the same main freq in the states), and the power is so low that it doesn't even show up on the spectrum analyser.

ILS Localisers and VOR's operate in the VHF band (around 108-117MHz), and our VHF Transponders do not affect the approach angle whatsoever. The aircraft we use are Challenger aircraft. We have 2. They are #1 and #2 in THE WORLD, with the most mileage. This being said, it may be possible that the coaxes could be damaged (they are maintained, but im not certain on the interval since i don't fix airplanes).

Hope this stimulates your thoughts.

Cheers.

 

[gcgrotz]

NAVCAN: Thanks for the interesting post and nice to know our northern neighbors are reading along here. I think it is especially interesting that the VHF transponders don't interfere with with VORs. They must have good front ends with VOR band selectivity, unlike my scanner!

Since I work in the wireless phone field I thought I'd throw out an FYI.

Here in the states there are CDMA systems on both 800 and 1900 MHz. It just depended on which spectrum a carrier ended up with in which markets. Most phones will work on either band. Regarding the power level, one of the basic standards in CDMA is that the base station is constantly (I think it is up to 800 times/minute) telling every mobile in its range to adjust its tx power so it is hearing all mobiles at the same level; that level being just at or slightly above the noise floor. I have a phone that displays TX power in -dbm figures, it will go into the -40 to -50dbm range when I'm at a site standing under the tower. That's a few tenths of a microwatt for the uninitiated. I think the highest a CDMA phone will go is 200milliwatts. Typically, they operate with less power than your home cordless phone.

Just curious, do you use CDMA phones while in the air and if so when do you experience problems - altitudewise? I know around here on mountaintops they won't work well if at all due to too many interfering carriers and digital garbage caused by lengthy propagation delays.

 

[Yokoshibu]

CDMA shouldnt experience any problems in the pattern, (low and slow) below the 10000 feet where you have the 250 knot airspeed restriction it shouldnt have a problem keeping a connection once you get up in altitude I have heard of them maintianing a connection but they drop like a mofo cause the phone cant handle the queries from the sites.... that and the fact you are in a tin can is why the battery drains... more reasons for me to turn my cell phone off, and sat phones work better anyways.