Jump to content

Radio noise on receive...


Stuart

Recommended Posts

Our CTLS has an SL40 that's been working fine for more than a thousand hours. That changed a week ago and we're having trouble tracking down the trouble.

 

The radio is transmitting properly according to every radio test I perform with other pilots on the frequency. It's quiet on the receive side until any transmission breaks squelch. Then, strong signals are understandable through a pulsing noise that garbles the audio. Weaker signals are drowned out by the noise and uninteligible.

 

I did a 180 and returned to my home airport last Saturday when, at about 20 miles away I could no longer understand ATC. I was on my way to an airshow and didn't want to continue into the heavier traffic without being able to understand traffic instructions.

 

Back at the hanger I pulled the center panel and took a look for any loose wires or other obvious trouble at the back of the radio. The only thing I found was a missing nut on the antenna connector ground plane tab. The other side of the tab was still tight.post-873-0-04352900-1373855341_thumb.jpg

 

I'm including a picture of the connector and the nut. You can see the nut in place in the antenna connector shot. Once I removed the nut so I could compare it to a new one for size I discovered it's a little different. That's shown in the second attached photo.

 

I found another nut that fit the thread and though it didn't have a shoulder like the original nut at least I could tighten the connector. Testing the radio in the hanger with the engine off results in clear received audio. I decided to go on a test flight. As soon as I started the engine, AWOS got very noisy. I shut down and put it away.

 

Is there something on the engine that could be bad and causing this

when the engine's running since the radio works when the engine is off?

 

Stuart

post-873-0-64111200-1373855354_thumb.jpg

Link to comment
Share on other sites

I had the exact same symptoms.

 

After I tried to isolate the problem in the cockpit and then several visits to the avionics shop on the field ($180), quit by accident I found out the problem was SQUELCH.

 

Check and adjust SQUELCH on the PM3000 & SL40. Chances are 1 of them is source of the problem.

 

Naturally no warranty expressed or implied. Your mileage may vary. yada...yada...

Link to comment
Share on other sites

The replies about the capacitor were spot on! Based on your suggestions I discovered a broken lead on the capacitor. Replaced it with a new one and all is well on the radio!

 

Thanks again.

 

Stuart

 

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...