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HELP! Call-out to Avionic Techs

terrykohler

Well Known Member
I just made an instrument flight from Michigan to North Carolina using my recently installed (not by me) GTN650. Nav side functioned fine the entire trip, but the COMM side (both TX and Rec) seemed to get progressively weaker until I lost contact with ATC half way down.
At my destination (KOAJ, Albert Ellis in Jacksonville, NC) I was barely able to hear the AWOS within 3-4 miles of the field, and my communication with local traffic was very marginal.
Ther are no techs on the field and I haven't been able to find any nearby so far.

Any suggestions for trouble shooting this issue myself before I try to undertake a VFR trip home without COMM? My backup is a hand held. Any work will need to be done on the ramp.
Thanks,
Terry, CFI
RV9A N323TP
 
Terry,

The first thing to try is to reseat the GTN-650 in the rack and make sure it is FULLY seated. I had a similar problem with my GNS-430W when it wasn't fully engaged in the rack.
 
Was the antenna also new? Take a good look at it and the connectors for proper grounding, or a poor coax connector where the cable is coming out.
Here's an easy test: removed the com coax connector from the back side of the GTN rack. Plug it into your handheld. If the handheld works well, then the issue is in the GTN box. Leave the handheld plugged into the coax (might need to cut cable ties to get it long enough) for the VFR flight home. Take spare batteries. OTOH if the handheld's reception is poor, the problem lies in the coax or antenna.
 
Proper antenna

Make sure the proper coax are plugged into the proper device and antenna. Use a multi-meter and confirm which cable is which. If the com is plugged into the wrong antenna, it will work but not as well as it should.
 
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Thanks Guys

Headed to the airport tomorrow to try your suggestions. Fingers crossed. Looking to head home Monday or Tuesday.
Terry
 
Radio Problems - Epilogue

Finally got the plane over to the avionics shop (about 40 NM from Pontiac). Long story short, I've been transmitting and receiving at about 50% strength with my new GTN650. It wasn't the radio or the connections. Turns out the installer had hooked my now-vacant market beacon antenna to the COMM connector on the back plate. When I was in Jacksonville, I only checked security of connections and didn't follow the wires. Their mistake followed by my mistake. Didn't really notice a problem earlier as my flying since install has been pretty much local. ILS and GPS worked fine, and I initially thought I was having intercom issues but was still communicating OK when close in. Another lesson learned.
Terry, CFI
RV9A N323TP
 
Finally got the plane over to the avionics shop (about 40 NM from Pontiac). Long story short, I've been transmitting and receiving at about 50% strength with my new GTN650. It wasn't the radio or the connections. Turns out the installer had hooked my now-vacant market beacon antenna to the COMM connector on the back plate. When I was in Jacksonville, I only checked security of connections and didn't follow the wires. Their mistake followed by my mistake. Didn't really notice a problem earlier as my flying since install has been pretty much local. ILS and GPS worked fine, and I initially thought I was having intercom issues but was still communicating OK when close in. Another lesson learned.
Terry, CFI
RV9A N323TP

Glad the fix was easy.

It also shows a good reason for putting labels on both ends of co-ax cables, even if they are only masking tape/sharpie ones...:)
 
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