The A220 is a 's4!??'y' radio. Save yourself a lot of headaches and use a better com.
ADS-B and transponder are about the same, not separate units. If you break it down, an ADS-B out system is a mode S transponder with a WAAS gps position piggybacked on the signal. I'm a big fan of NOT putting square radios in a Cub type panel as they were not designed for the trays. Go with the Becker AR6201 or Trig TY91 for a com and the TT22 for the ADS-B system. As Mr Pierce said, just add the TN70 GPS to the TT22 to turn it from a transponder to an ADS-B system. All of these units are designed to fit into the panel with no mounting tray.
I've never heard of a TY91 being weak. Show me a 'weak' one and I bet I can show you an improperly installed antenna.
As for the static on your radio, do some basic troubleshooting to find the source of the noise. Turn off the alternator field and check for noise. Then do your mag check and see if the noise goes away when you switch to one mag or the other. If you still have the noise, start pulling the circuit breakers one by one until the noise stops. Fix the source of the noise, don't try to mask it with filters.
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