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Help with static in headset

jhk770

Active Member
I decided to go for my instrument license and I am in the process of equipping my already flying RV7A for IFR. I currently have a SkyView, SL40 and a garmin audio panel. So far I have installed a GPS antenna, a comm antenna and a wing tip VOR antenna for a future NAV/com. I also replaced the antenna that?s as originally installed with a matching bent whip. The comm antennas are about 28? from each other on the belly. I ran the coaxial cables up under the panel and are coiled up. The coaxial is only connected to the antennas, don?t have any BNC connectors on the coiled up ends and aren?t connected to anything under the panel. I didn?t change anything on the old comm coaxial. I just connected it to the new antenna.

However, I went for a test flight and I now have horrible static on all frequencies. I was able to transmit to ATC and they said it sounds good, but I have trouble hearing anything over the static.

In the past, I have had this same problem but not nearly as bad now and again; only on 122.95, my home field frequency, but when I flew away it would stop. I thought it was just some kind of local interference in one of the hangars and it was never on any other frequencies.

Is it possible that the new coaxial that is not connected to anything is interfering somehow? Should these be terminated?

Can anyone out there give me an idea on where I should start to look to solve this.

By the way, it is not any of the lights as I have shut everything off.

Thanks,

Jim
 
Diagnosing avionics via remote vision is very hard. But, my suggestion: Since ATC said you sounded okay, I don?t think this is an antenna issue. if your audio panel has ?fail safe?, turn it off. Noise still there? Go into the SL40?s set up menu. Check out the squelch settings. Turn off the SL40 to make sure it?s the source of the noise. Try powering off everything except the SL40. Noise still there? Report back.
 
I agree diagnoses of a remote comm problem is nearly impossible. However, I once had trouble with static as you describe and discovered the coupler from the radio to the antenna was frayed. I cut the old connection off, installed a new coupler connection and the static disappeared.

Contact Steinair and they can sell you the connection and proper tool to crimp the connection. They also have a useful video on how to do this on UTube.
 
Jim-

Try this easy suggestion ... Make up a pair of jumpers ..... Connect one end to a good ground and the other end to the coax making sure to ground both the BNC and the center pin together. Do this for both of the unused antenna coax cables.

If this solves the issue you can make a connector that permanently grounds out both coax cables until you are ready to add the new gear.
 
Thanks for all the suggestions.

I checked continuity and all seems good.

I believe it is a coincidence that it happened right after the recent work as I have had this issue a few times in the past as I said, but not nearly as bad.

I went to the airport yesterday and did some troubleshooting. It seems the SkyView is creating some noise, I think... because when I turn it off it goes away, but again I didn?t fly with it off and the noise came and went. However, yesterday it was happening on 122.975 while in the vicinity of my home field while on Friday it was on all frequencies. It happened a few times on other frequencies also yesterday, but it seemed random. I also was using a new to me ANR headset on Friday. Don?t know if that has anything to do with it. I kept changing out headsets and used both the pilot and copilot jacks to see if that helped. Seemed to happen less, but not conclusive.

It seems like the squelch on my radio is intermittent as it sounds exactly the same as if I pulled the squelch knob completely out. The weirdest thing is on Friday with all my equipment off, I had the problem on my handheld radio in the hangar. Very weird. (There are a lot of LED spot lights around so that could explain that)

After flying, I decided to go into the settings of the SL40 and adjusted the squelch from 30 to 45. I will see if that helps. Anybody with a SL40 radio can tell me what number theirs is set at?

The good thing is the work I did seems not to be the culprit.

I?ll let you know if I find anything more definitive.

Jim
 
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