Radio Problems

[Syed Zaki]

My radio is clear on the ground and also on air for 20 minutes. After that no one can hear on approach frequencies, or on tower frequencies when coming back to home airport. I have heard from a few people headset could be a problem, audio panel could be a problem, intercom could be a problem or the electrical charging system. Can anyone shed some ideas on where to look.
Thanks
Bellanca SV owner

 

[MBDiagMan]

Do you have Volt meter on the panel? It sure would be a good start to make note of battery voltage once stabilized before takeoff and then see what it is when the problem is present.

 

[Dan Thomas]

Sometimes the radio itself needs work. Something inside fails when it gets warm.

And sometimes circuit breakers are shot. Their contacts oxidize and introduce resistance and that gets much worse when that resistance results in heating. You'd have to have a voltmeter on the 12V feed into the radio to spot that. If there are multiple radios on one breaker, and the rest work OK, the breaker is probably fine.

 

[Syed Zaki]

I have an ammeter that shows alternator charging or discharging or neutral as more equipment are used. No voltmeter. Voltage from the battery is good, voltage to the buss bar is also ok. I’ll check the breaker tomorrow. Intercom is a separate unit and someone suggested that could be causing the problems with radio. Could it be the alternator and the charging system? Replacement radio didn’t work well either. ATC and tower had trouble with hearing me on the way back and complained about the bad radio. No complaints on departure.

 

[Daleandee]

You note that departure is good and the first 20 minutes. If this is when you are close to the airport and going away from it the concern may be in the antenna and not the radio. An antenna with poor SWR due to corrosion, loose/dirty connections, or worn coax may work fairly well over a short distance but very poorly at greater distances. Don't be fooled by the fact that you can hear approach from a long way off. A poor antenna SWR will hear much better than it will transmit.