Crackaly weak transmit

This is weird, have you seen this before, my setup, full Dynon system with a single Dynon com radio and two bent whip Delta Pop com antennas, one for emergency hookup to handheld, not used. Intercom works good on both sides, receiving broadcast from other aircraft and ATIS fine. First thing I did was remove antennas and confirm good clean skin on inside skin and backup plates, good continuity between antenna mounting studs and inner skin-airframe ground. unhooked BNC connectors at both ends, OHM cheeked out good. reconnected and tested again, no change, out of curiosity I switched the antenna to the other antenna and all is well? both antenna cables OHM out the same? what the?

You changed the antenna; were you using the same coax, or the "backup" coax? Sounds suspiciously like a bad connector somewhere.

Yes, hooked up the other antenna with the other coax and it worked, so, bad coax we are thinking.

An ohm meter only checks dc. You are using 118-136 MHz. Acts totally different. This is where a vswr meter or an old school watt meter work. Can you swap the antennas to rule them out?

I have a completely different setup than you but when I had this issue with my Commant antenna, I removed one screw from the base, gave the hole a couple of turns with my deburring tool, applied some dielectric grease, replaced the screw and moved on to the next one.

The issue was a bad ground and this solved it.

Antenna

I have been fighting a similar problem for quite a while. If the antenna fix works for me an extra $25 is going to Doug.

I did make these BNC connections, so it is totally possible that I messed one of them up, Funny, it was working, then not, and now it is working with the other antenna and cable but I would like to know what is going on with the other one, I will measure the pin depth and then a destructive autopsy. has anyone done a small current load on the bench while doing a voltage drop test?

bret said:

I did make these BNC connections, so it is totally possible that I messed one of them up, Funny, it was working, then not, and now it is working with the other antenna and cable but I would like to know what is going on with the other one, I will measure the pin depth and then a destructive autopsy. has anyone done a small current load on the bench while doing a voltage drop test?

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As Jay mentioned above, performing DC testing on this cable is unlikely to tell you anything useful. You really need a VSWR meter to check this cable and antenna at VHF frequencies.

Knowing Don, I would doubt it's an antenna problem. He tests every one of his antennas before shipping.

First thing I would be inclined to do is swap your known good coax over to your suspect antenna. If all that works, then you've isolated the problem to the cable and you know it's not an antenna problem or an antenna grounding problem. If you get the same crappy results, however, then the cable is good and you know it's either the antenna or the antenna ground. In that case, focus on the easy (cheap) things first. Remove mounting nuts, ensure you have a star washer contacting the skin, good clean skin contact area, etc. If none of that helps, you can always send the antenna back to Don and he can test it out.

Good luck!