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  #1  
Old 02-02-2018, 08:58 PM
backcountry backcountry is offline
 
Join Date: Dec 2015
Location: Houston, Texas
Posts: 26
Default Noise on the GTR 200 Com.

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.
Iíve checked the grounds and the antenna connections.

Yesterday the temperature was in the 70ís 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 50ís.

Any ideas?
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  #2  
Old 02-02-2018, 10:26 PM
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rongawer rongawer is offline
 
Join Date: Dec 2007
Location: Brentwood, CA
Posts: 326
Default Jacks

A very common cause of radio noise is the headset jacks. It could be that youíre getting a temperature induced ground, or it could just be movement of wires or shielding. Iíd check the jack insulating washers, try swapping headsets, or use the copilot jacks for a test.
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  #3  
Old 02-03-2018, 06:47 AM
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g3xpert g3xpert is offline
 
Join Date: Sep 2010
Location: Olathe, KS
Posts: 2,005
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Quote:
Originally Posted by backcountry View Post
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.
Iíve checked the grounds and the antenna connections.

Yesterday the temperature was in the 70ís 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 50ís.

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
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  #4  
Old 02-03-2018, 08:28 AM
mturnerb mturnerb is online now
 
Join Date: Apr 2015
Location: Ponte Vedra, FL
Posts: 698
Default

Quote:
Originally Posted by g3xpert View Post
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.
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  #5  
Old 02-04-2018, 06:58 AM
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rvanstory rvanstory is offline
 
Join Date: Dec 2016
Location: New Braunfels
Posts: 127
Default

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/vie...hp?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.
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  #6  
Old 02-04-2018, 03:47 PM
backcountry backcountry is offline
 
Join Date: Dec 2015
Location: Houston, Texas
Posts: 26
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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 havenít had a chance the other items.
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  #7  
Old 02-05-2018, 07:26 AM
bobnoffs bobnoffs is offline
 
Join Date: Jul 2012
Location: n. wi
Posts: 529
Default

scary scary
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  #8  
Old 02-05-2018, 03:16 PM
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g3xpert g3xpert is offline
 
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Location: Olathe, KS
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Quote:
Originally Posted by backcountry View Post
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
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Please email us for support instead of using Private Messaging due to the limitations of the latter.
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  #9  
Old 02-05-2018, 04:06 PM
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9GT 9GT is online now
 
Join Date: Jan 2010
Location: Southern Michigan
Posts: 1,465
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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.
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  #10  
Old 03-22-2018, 10:04 PM
backcountry backcountry is offline
 
Join Date: Dec 2015
Location: Houston, Texas
Posts: 26
Default

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 hasnít returned.
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