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Noise on the GTR 200 Com.

backcountry

Well Known Member
I started flying this aircraft June 2017 the GTR200 com. worked fine for approximately 60 hours. Starting in December the problem now is after about 15 minutes into the flight you start hearing a noise that building to a full squelch noise. If I turn the unit off and leave it off for a while it seems to come back with less noise and then build. Back on the ground and the radio seems normal.
I?ve checked the grounds and the antenna connections.

Yesterday the temperature was in the 70?s and the GTR 200 worked perfectly normal for the complete flight, the first time since the problem began.
However, today I flew the aircraft again and the problem is back. Note, the temperature was in the 50?s.

Any ideas?
 
Jacks

A very common cause of radio noise is the headset jacks. It could be that you?re getting a temperature induced ground, or it could just be movement of wires or shielding. I?d check the jack insulating washers, try swapping headsets, or use the copilot jacks for a test.
 
I started flying this aircraft June 2017 the GTR200 com. worked fine for approximately 60 hours. Starting in December the problem now is after about 15 minutes into the flight you start hearing a noise that building to a full squelch noise. If I turn the unit off and leave it off for a while it seems to come back with less noise and then build. Back on the ground and the radio seems normal.
I?ve checked the grounds and the antenna connections.

Yesterday the temperature was in the 70?s and the GTR 200 worked perfectly normal for the complete flight, the first time since the problem began.
However, today I flew the aircraft again and the problem is back. Note, the temperature was in the 50?s.

Any ideas?

Hello BackCountry,

You say "you start hearing a noise that building to a full squelch noise".

If possible, it would help to isolate the type of noise you are describing. The GTR 200 has a built-in intercom and can receive audio signals from headset mics, dual mono aux (alert) audio inputs to play stall/terrain/obstacle/traffic warnings, a stereo music input, and of course a radio audio receiver.

If, for example, you were getting noise on an alert input, you might hear it as you describe.

Which of these inputs are introducing the noise?
1. Aux (alert) inputs (connected to your EFIS system?) Each of the aux audio inputs has its own volume and squelch setting. As a test you could set the aux audio input volume that you are using to zero and see if the noise issue goes away. You could also try raising the aux squelch setting for that input, but make sure the alert audio generator can still break that squelch.
2. COM radio audio: When you hear noise, do you see the RX icon on the radio indicating that the radio is receiving an external RF signal that is in excess of the receiver squelch threshold? Does the noise level change when you change the radio volume?
3. Intercom audio: When you hear this noise in your headset, is it because there is an open intercom channel in the aircraft? Does the noise volume decrease when you decrease the intercom volume setting? When you hear this noise, you could try unplugging your mic jack or the passenger mic jack and see if the noise goes away. Some people try to fly solo with a passenger headset plugged in, and this can also cause the intercom to open if the headset mic is in the wrong place.
4. Music input: Try turning the music off at the GTR 200 and/or turning the music volume all the way down to make sure the noise isn't coming in on the music input.

Thanks,
Steve
 
Hello BackCountry,

You say "you start hearing a noise that building to a full squelch noise".

If possible, it would help to isolate the type of noise you are describing. The GTR 200 has a built-in intercom and can receive audio signals from headset mics, dual mono aux (alert) audio inputs to play stall/terrain/obstacle/traffic warnings, a stereo music input, and of course a radio audio receiver.

If, for example, you were getting noise on an alert input, you might hear it as you describe.

Which of these inputs are introducing the noise?
1. Aux (alert) inputs (connected to your EFIS system?) Each of the aux audio inputs has its own volume and squelch setting. As a test you could set the aux audio input volume that you are using to zero and see if the noise issue goes away. You could also try raising the aux squelch setting for that input, but make sure the alert audio generator can still break that squelch.
2. COM radio audio: When you hear noise, do you see the RX icon on the radio indicating that the radio is receiving an external RF signal that is in excess of the receiver squelch threshold? Does the noise level change when you change the radio volume?
3. Intercom audio: When you hear this noise in your headset, is it because there is an open intercom channel in the aircraft? Does the noise volume decrease when you decrease the intercom volume setting? When you hear this noise, you could try unplugging your mic jack or the passenger mic jack and see if the noise goes away. Some people try to fly solo with a passenger headset plugged in, and this can also cause the intercom to open if the headset mic is in the wrong place.
4. Music input: Try turning the music off at the GTR 200 and/or turning the music volume all the way down to make sure the noise isn't coming in on the music input.

Thanks,
Steve

I had a very similar issue and #4 was the cure. The music input was picking up noise.
 
FWIW, I had a radio noise issue in the Mooney I currently fly. It was intermittent and very hard to find the issue. (my avionics shop wanted to replace the audio panel).

Turned out to be the USB charging plug I used to keep my iPad charged in flight. It plugged into auxiliary power plug (aka, cigarette lighter plug). It would create RF while charging, go away when fully charged.

Turns out, Google is better at diagnosing this problem than the avionics shop. Google "usb charger causing rf interference in planes". Here's a sample of what will pop up.

https://www.beechtalk.com/forums/viewtopic.php?f=7&t=81803

I had used this same plug for months with no problem, so not sure why it started making noise when it did. Took a new $7 usb charging plug to fix it. Now I'm noise free and still have the $3k a new audio panel would have cost in my pocket.
 
Item #2 does apply in my case.

The RX icon starts out flashing on and off as the noise starts but goes solid as as the noise increases.

I haven?t had a chance the other items.
 
Item #2 does apply in my case.
The RX icon starts out flashing on and off as the noise starts but goes solid as as the noise increases.

I haven’t had a chance the other items.

Hello Backcountry,

Ok, you have confirmed that the noise you are hearing is an RF signal breaking squelch on the COM radio receiver itself. This should rule out intercom, aux input (alert), or music audio inputs in general. Based on your observation, if you turn the radio volume all the way down when this happens, everything is quiet in your headset.

I would start by making sure that power grounding and coax shield grounding is good and your coax connectors are good. I would also make sure the antenna ground is properly grounded to the skin of the aircraft.

You mention that this is only a problem when airborne, so it might be related to vibration or ignition/alternator noise, but that could just be a side effect of a shielding/grounding issue.

When it occurs in flight, you might also try load shedding non-essential electronic devices to see if you can cause the problem to go away (RX annunciation stops) to pinpoint the source of the interference.

In some cases people have had to separate the COM antenna coax cable from other wiring in the aircraft.

Thanks,
Steve
 
I had a similar issue with the GTR 225 I had in my RV-10 when I first started flying it. I isolated the noise doing load shedding as g3xpert suggests. My noise was coming from el cheapo LED power supply in the rudder for my tail position light. I replaced it with a high quality one and that solved the issue for me. It would be barely noticeable on the ground but as I obtained altitude after take off it got louder to the point I could barely hear anything in the headset but white noise.
 
Feedback on the noise in my GTR200 Com.

It looks like it was as the connection between the com connector and the 50001 box. When I unplugged and reconnected the com cable to the 50001 box the noise stopped and hasn?t returned.
 
After 7 months the noise again returned. Sounds like squelch noise. Again I removed and reinstalled the comm connector on the 50001 box and once again the was gone but didn?t last very long.
Has anyone seen this problem?
Vans eliminated the box on the new RV-12?s.
I feel as the aircraft ages problems will increase considering all those connections on the 50001 box.
 
After 7 months the noise again returned. Sounds like squelch noise. Again I removed and reinstalled the comm connector on the 50001 box and once again the was gone but didn’t last very long.
Has anyone seen this problem?
Vans eliminated the box on the new RV-12’s.
I feel as the aircraft ages problems will increase considering all those connections on the 50001 box.

Make sure it is not a problem related to the grounding of the box itself.
It is supposed to have a good ground to the airframe (I think internal tooth lock washers are used on the mounting screws to help with this).
When you R & R the harness cable you might be moving the box enough to influence the ground connection.

Also be sure that all pins are fully engage in the harness connector.
 
I had the same issue in my -4. It turned out to be the power cord for the Garmin 495. If I unplugged it, the sound stopped. I never did find a fix for it. I just ran the 495 on battery power and took it out of the airplane to recharge it every 10 hours or so.
 
Also, try removing and re-seating the GTR200... fixed a crazy intermittent problem we were chasing on/off for months.
 
I?ve tried everything I can think and the ideas made here.
Latest update
Noise cable suppressors added to 3 cables coming from the 5000 box.
Comm
Options
Autopilot
This seems to get rid of the noise. I don?t know what the real problem is but I suspect it in the 5000 box.
Thanks for the ideas
 
Fix for this issue

I had the same issue in 2 RV12's with the GTR200 and was able to fix both. The problem is that mounting bracket for the GTR200 has a floating backplate.

The cable harness that goes into the back of the radio is wiggling with the vibration of the plane. So, it causes the problem intermittently.

You will need to take of the top panel above avionics to get to the back of the mount. There are 2 metal tabs that go through a small opening on both sides of the harness. You will see where the backplane attaches to the rest of the harness.

I took a couple of small screws and shimmed both sides so the Harness can not wiggle anymore and the problem went away.

--Good Luck.
 
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