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transponder overpowers comm radio (Read 337 times)
Oct 27th, 2018 at 7:17pm

Jim H   Offline
New Member
I love flying!

Gender: male
Posts: 2
Inspected the coax which is new.
Did not find any issues.
Separated both coax cables from each other by a minimum of 1 foot.
Removed the transponder from it's mounting plate and held it a foot away from the comm radio and still kept the transponder case grounded.
Transponder antenna is on bottom of plane; comm antenna is on top of plane, 2 feet behind the wing.
None of these things made any difference.
Still noise in the headset which sounds like Morse code and a clicking noise.
Comm radio transmit to the control tower is still poor.
Garbled and broken; weak signal.
reception has never been a problem
Remove power to the transponder and Morse code and any other noise is gone and transmit is loud and clear.
any thoughts?
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Reply #1 - Oct 28th, 2018 at 9:40am

mmarien   Offline
Murray M.
Saskatoon SK CAN

Gender: male
Posts: 1188
I had a problem with the ADS-B transponder flooding my pitch servo with RF and making it go offline (composite a/c). I moved the antenna and problem went away. With one antenna on top and one on bottom you'd think there would be enough separation. Perhaps try moving one antenna.

Glasair II FT - o320 - P-Mags - EFII - MTV 3 Blade CS - VP-X - Single 10" Skyview - Stratux Dual Band - zooooom ...
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Reply #2 - Oct 29th, 2018 at 10:47am

RayInGA   Offline
I love aviation!
Richmond Hill, GA

Gender: male
Posts: 590
Coax wire shielding is grounded at both ends to keep EMI from affecting other components. I'd suggest you confirm you have good shield grounding at both ends of the transponder.

You can also increase the squelch on the radio (within SV setup) but, based on your symptoms, that probably won't help.

Ray Eaker
RV-7A flying since 27 Jan 2017
Dual Skyview 1000T with all available Dynon VFR goodies
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