I did a bunch more troubleshooting this weekend. I found that the intercom failure was due to a bad connection I made when I replaced one of the connectors at the intercom. I fixed that yesterday, and now the intercom and the MicroAir 760 (COM 2) are working again. But the GNS 430 (COM 1) is still dead.

I confirmed good connections from the front seat mic jack all the way to the GNS 430, with the intercom ON and OFF. The PTT connection at the GNS 430 rack is pulled to ground when I press the PTT switch. I reconfirmed good power and ground connections at the COM pins at the 430 rack.

Today I removed the front seat and the floor so I could get at the antenna. I confirmed continuity from the antenna connection at the rack to the antenna, and no shorts between the coax centre conductor and ground. I found the coax connector loose at the antenna - it was not fully turned until it locked. I found that the end of the coax connector would hit the doubler on the inside of the skin slightly before the connector was locked. I was able to get the connector to lock using a pair of pliers, but I realize now that what I probably should have done instead was enlarge the hole where the antenna’s coax connector comes in from the outside so it was larger than the coax connector diameter. I’ll do that next time I’m back at the hangar.

I went flying this afternoon to do another radio check. No one would talk to me on either radio, which really bummed me out. After landing, I saw that Alfio and Shirley’s RV-9A was parked on the ramp, so I went down to the club house hoping to get them to man the club house radio while I did a radio check (the Smiths Falls Flying Club has no permanent staff, so there is usually no one at the radio). But, they started up and taxied out before I got there. I found Fred, a local C-172 pilot, in the club house who had landed just before I went flying. He had heard me on the radio, so that suggested that COM 2 at least was working. He offered to man the radio while I did a radio check, which confirmed that COM 2 was working but there were no signs of life from COM 1, not even carrier. Hmm.

I’ve ordered an ICOM A-6 handheld COM, which should greatly help in the troubleshooting. I also ordered some coax cable and connectors so I can temporarily hook up the GNS 430 to the COM 2 antenna. That should help determine whether the problem is the antenna or wiring. I also look at hooking up a way so that I could hook up the handheld COM to the COM 1 antenna when needed in flight.

I also made another adjustment on the prop coarse pitch stop, and now have clearly gone too far, as the rpm increases to 2800 rpm as I get to VNE. I’ll set it about half way between the two previous settings and check it again.