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I'm trying to figure out my transponder issues. Any basic info would be helpful, along with guesses on diagnostics.

I have a 2011 CTLS (serial F-11-03-05) with twin Dynon Skyview PDFs. There is no visible transponder in the panel. All transponder controls are accessed through the PDFs, by hitting Transponder button. From there I can turn the transponder on or off, set mode "C" (alt), set the transponder code and "ident", if asked. I do have a separate Transponder breakers.

Recently, Centennial Tower has been telling me that my transponder is unreadable. Sometimes, they say they can read only my "target" with no altitude. Then, at other times they say it's totally in-op.  When I recycle the transponder (by pulling breaker and re-setting it), the controller tells me its back and working. But eventually it fails again. The controller added detail ... and said it goes in an out, on downwind, then back on again in the base turn. They said it seemed like a "signal problem".

I should mention that during the whole flight, the PDF shows normal (green display) transponder operation (except when I pull the breaker).

QUESTION:  What would make the transponder appear intermittently? While appearing "normal" on my PDF displays?

I already checked antenna connection. It appears to be secure.

QUESTION:  Is the transponder a separate unit? Or is it contained within the Dynon Skyview PDF?

IDEAS?

Thanks!

-Tom

 

 

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I have a Garmin 327 which is totally different than your setup.  However, your description sounds very familiar when i had transponder problems.   Mine turned out to be a bad connection from the transponder to the mounting bracket - which was off by as little as 1mm   (which was basically a bad connection to the antenna).    My non expert advice is to double check what 'appears' to be a good antenna connection and make sure 100% that it is.    

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Transponders are extremely high output devices.

Some old trabsponder models in GA would shut down automatically if they were overheating.

I doubt the dynon transponder is overheating but still, something to think about.

Antenna connections also need to be clean and solid.

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A lot of different issues can cause your problems, frequency, side lobe suppression, mtl, etc. You need to have a test box put on it. Usually I could find the problem in minutes. Should't cost much to do this. I could usually do this in 10 min. Fixing it  will take longer. Its not like having everything in one box like a 327.

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Any avionics shop can radiate the transponder signal to the test set and determine the issue. As far as putting the transponder box on the bench for adjustments I don't know. I would assume there is some specialized interface to take the place of the PDF. I am sure it would be a shop that deals with Dynon equipment. If there are any issues with the radiated test it might be easier  to send the unit to Dynon. You would still have to have it recertified in the aircraft after getting it back.

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You undoubtedly have the Dynon transponder. I would first check the antenna connections at the transponder and antenna.

Another possibility is the connections to the Dynon panels - the transponder is connected to both. 

Or, it may be in the transponder itself. If you are not an LSRM-A and comfortable with electronics it would be best to take it to an electronics shop.

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