1090mhz ADS-B / noise cancelling Headset noise.

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1090mhz ADS-B / noise cancelling Headset noise.

Post by Lance Murray »

Has anyone else here experienced noise in their headset after installing a GTX345 or other ADS-B 1090mhz transponder? I get a snapping noise in my noise cancelling Bose A20 headset after the install of the transponder. It is for sure coming from the transponder. The noise is present even when the headset is powered on and completely unplugged from the aircraft. See thread below.

http://www.vansairforce.com/community/a ... 47411.html
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Re: 1090mhz ADS-B noise cancelling Headset noise.

Post by smoss »

yes, I have always gotten a similar noise in my Telex headset, particularly with its music input setting umuted, both with my original transponder, and new GTX345R transponder. You can modulate how loud it is by placing the headset control module in various spots--floor in back seat is the loudest (right above transponder antenna), on my lap is nearly non-existent. My cheap headsets do not produce this noise at all, but even one of my Telex passive headsets does. It seems brand specific in how well they are insulated again this noise.
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Re: 1090mhz ADS-B / noise cancelling Headset noise.

Post by Boatguy »

I have used both Bose A20 and Lightspeed Zulu3 and don't hear any noise. It may be Bluetooth related if Bluetooth is active on the headset.

You could try some temporary shielding around the area of the GTX345R and see if the noise goes away.
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Re: 1090mhz ADS-B / noise cancelling Headset noise.

Post by smoss »

it's not from the actual transponder, it's from the antenna on the bottom of the plane--my control box directly over it is where it is the loudest.
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Re: 1090mhz ADS-B / noise cancelling Headset noise.

Post by Lance Murray »

I recently checked for this noise on my Experimental airplane with a GTX345R and G3X system. Same noise is present. Headset not plugged into the airplane. The Bose picks up the noise from over 10 feet away from the antenna. Interesting to me that the Avionics shop was unaware of this despite installing quite a few ADS-B 1090MHZ transponders. They do work on mostly government helicopters and a lot of those pilot wear helmets instead of noise cancelling headsets however.
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Re: 1090mhz ADS-B / noise cancelling Headset noise.

Post by Colin »

I bet a little Faraday cage around the control box would eliminate it.
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Re: 1090mhz ADS-B / noise cancelling Headset noise.

Post by Rich »

I made a special effort today to confirm, but I haven't ever noticed this after 5 years using a KT74 with several ANR headsets. The transponder antenna is right below my seat, the headset control box along my right leg, and the transponder about 1 foot away from the control box in the front panel. The cabin is also awash in WiFi and Bluetooth communication. :D
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Re: 1090mhz ADS-B / noise cancelling Headset noise.

Post by smoss »

Colin, is that a feasible option? How would I try that?
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Re: 1090mhz ADS-B / noise cancelling Headset noise.

Post by Steve »

I've also noticed this in my airplane after adding ADS-B out (UAT: GDL-82 and existing KT76C transponder). In my case, it sounds like the intercom breaks squelch for a split second. I have an old (> 20 years) David Clark ANC headset. I tried various experimental conditions to get rid of it, and found that it would not occur if the Phone plug for the Copilot headset was unplugged! That headset isn't even ANC.

Since I am in the midst of my annual, I took the opportunity to add a bit of RF blocking:
IMG_3808.jpg
I'll let the group know if this works...

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Re: 1090mhz ADS-B / noise cancelling Headset noise.

Post by Colin »

Colin Summers, PP Multi-Engine IFR, ~2,600hrs
colin@mightycheese.com
http://www.flyingsummers.com
N972RD DA42 G1000 2.0 s/n 42.AC100
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