My left comm antenna has seemingly always been weak. It's connected to the GTR 200, whereas the right comm antenna connected to the GTN 650 has consistently provided better performance. So I measured the left comm antenna with my cheap vector network analyzer. The left image shows the SWR (blue line), |S11| (blue) and the complex S11 (green). The SWR is > 11 and the complex S11 has a rolling phase and high magnitude. Clearly, the matching network in the antenna is faulty.
The right image shows the same measurement on a properly functioning comm antenna. The SWR drops over the airband and S11 is much more stable.
I ordered a new antenna from Delta Pop Aviation. The new antenna is shorter with a more aggressive bend when compared to their older, as shown below.
My belly looks like the below after replacing the left antenna with that new one. I wasn't too excited by the asymmetry (I guess I suffer from "airframe vanity").
Delta Pop kindly sent me a new one for no charge to replace my broken one, even though it was 9 years old already.
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