The International Cessna^® 170 Association

I have an IA rewiring my radios and installing an audio panel. All is done, but we are experiencing a problem & thought it might be something someone out there would have also experienced and have a valid suggestion. I have an ICOM A-200 & A-210 in my stack. Both are now receiving & transmitting OK. However, when transmitting on the A200, it causes the A210 to flip frequencies each time the ptt is pushed (just as if I were pushing the frequency flip/flop button on the A210). The units have all been wired per the specs. ICOM tech support states they have never heard of this problem before and were unable to offer any assistance The only thing they suggested after discussing the problem with my IA is that it might be possible that the problem is that we have checked these radios out "IN THE HANGAR" and there "might" be an RF situation that has caused the A210 to flip/flop the frequencies with each ptt of the A200. Transmitting on the A210 does not cause the A200 to do this dance. We were going to pull the plane out of the all metal hangar today to see if that had anything to do with the problem, but with the snow we won't do so before Friday or early next week.

I guess the 100 dollar question would be why would RF cause the radio to flip-flop?

Does the A210 have the capability for a remote flip-flop button that you hadn't intended to wire? That is were I'd be looking while your waiting for the snow to melt.

Bruce, I have no idea how RF could affect the flip/flop frequency of the radio That was just what the ICOM tech mentioned to both me and my IA who is an EE & quite knowledgeable on avionics. However, he isn't too familiar with ICOM's. And for my part when the discussion of RF comes up you might as well be discussing the theory of relativity because I know NADA about how all of that works That 210 does have the capability of having it connected to a GPS so when an airport identifer is put into the GPS it automatically brings up the frequencies of that airport. Of course that likely isn't related to this issue. It also has the capability of having a remote button on the yoke where one can flip from one frequency (active) to another one (stand-by) rather than reaching up to the radio itself. You may be correct that that may have accidentally been wired in. (Still like the A-200 better than the more capable A-210) I will toss this to my IA and see if he can chase it out. I appreciate the suggestion. (You need to come down here tomorrow for the mid-year bod meeting and advise us Texans what this white stuff is that keeps falling We aren't used to seeing this 3 or more times a year )

My guess (and it's worth what you paid for it) is that the remote flip-flop is wired incorrectly. This would of course mean that your EE/IA made a mistake and therefor it is much more probable that some weird force in the universe is causing your radio to perform a function that it is designed to perform, but otherwise not being commanded to do by it's human operator.

You might try swapping the radios (I assume they use the same tray). If you swap their position and transmit on the 200 and it still makes the 210 flip-flop, then either your IA wired BOTH connectors wrong (doubtful) or it's something else. My guess is everything will work fine in this configuration. You might also try removing the 200 and press the PTT switch as if you were transmitting on it. If the 210 still flip-flops, then it's definitely not RF or anything necessarily related to the 200.

I've also seen where those bazillion pin connectors are plugged in, sometime the pin will get bent and make contact with an adjacent pin and cause all sorts of anomalies. I'd pull the connectors loose from the tray and look real closely and see if any of the pins are bent.

I'd guess PilotMikeTX is right.

Looking at the ICOM installation manual (see section 7, CONNECTOR INFORMATION in attachment), I see that the frequency flip/flop input is pin 12 and the transmit/receive interlock input is on pin N. These are directly across from each other on the connector. That would be a very easy error to make. Just sayin'.