Garmin SL 40 Radio Problem

[JJ Campbell]

I just moved my plane to an airport that has a temporary control tower. The first couple of times I flew out, all was well. Then suddenly, after I taxied to the run-up area, I could not hear the control tower nor they me. I have a Garmin SL 40 Radio from 2012.

The tower frequency is 127.5 and ground is 120.5. But, since there is only one person in the tower, everyone just stays on 127.5. When I could not hear the tower, I switched to 120.5 and it worked fine. I have come and gone several times and it is consistent. At my tie-down which is a few hundred yards from the RV that is being used as a control tower, I can communicate on 127.5. When I moved to the run-up area which is about a half a mile from the RV Tower, only 120.5 works (recall this is the same guy as 127.5). After I get in the air 127.5 works again. All the tower guys that have been on duty, say that I am the only one having this problem.

The avionics guy on the field used and old piece of test equipment and he could not find anything wrong. I called Garmin and several of the customer support people put their heads together and collectively, they all agreed they had never heard of a problem like this. Sigh.

I do not know if it is related but I normally use my Advanced Flight System 5600 to change the radio stations and it works fine. However, If I try the old-school twist the knobs on the Garmin, it sometimes gets cranky and wants to skip over numbers. So, I have given up even trying to do it this way.

Does any of this sound familiar to anyone?

[ShawnM]

Did the avionics guy test the antenna and the coax with an antenna analyzer?

[JJ Campbell]

Did the avionics guy test the antenna and the coax with an antenna analyzer?

No, he did not. He did not fill me with an abundance of confidence...