NavCom Background noise

[kitfox2009]

I have a Model 5 Vixen c/w 912UL. Navcom is a Terra 960. My problem is EXCESSIVE engine or electrical induced static and background noise when transmitting. It is so bad the tower cannot read me at all.

Today I temporarily installed a secondary battery (sealed unit from a small golf trundler) and connected this directly to the NavCom. It works great.

Has anyone tried the "Smoothy" from Miracle Antenna @ 129 dollars? I would gladly pay up if this would solve the issue.

Any SUGGESTIONS?? I have checked all the grounds, antenna connections, etc. It works great with the engine off!!

Cheers

Don Hudgeon

[Av8r3400]

I have a Terra 760 and found that the mic gain was set so high that the transmissions were often garbled. I now have that set to *just* above the minimum on the adjusting screw. Transmission is now much cleaner.

Another friend with the same radio had a similar issue and successfully cleaned it up by installing a double shielded coax for the antenna lead.

Do you have a capacitor on the power lead side?

[SkyPirate]

installing a .05 capacitor closest to the power in lead on any electrical devices will remove allot of noise,..

Chase

[kitfox2009]

Thanks Guys. I am replacing the capacitor next week and see if it is any better. Will also try the mic adjustment.
Thanks again.

Don

[RobS]

Av8r3400 already posted this as a possible cause, but I thought you might want to read what can be found at Bob Nuckolls which only confirms what he already posted about mic gain. See below . . . . .

>>Avionics: Radio Noise
I had a radio problem that sounds similar to yours. My transmissions were understandable on the ground (but not clear), but once airborn - while I could hear others perfectly clear, it was rare that anyone could understand me. I checked Antennas, connectors, etc all to no avail. Thinking the radio transmission might be overpowered by cockpit noise I even sprung $60 for a high noise environment microphone. No noticeable difference. One day an A&E type was at our little airport working on one of the FBOs plane so I mentioned my problem to him. He went out to the airplane, pulled my Terra 760 from its rack, took out a small screwdrive stuck it in a hole in the side and turned it approx 1/2 turn and told me to try it. It now works fine. It turns out the "mic gain" was turned up too high and was overmodulating the carrier wave causing "splatter" resulting in distortion. By turning down the gain it eliminated the overmodulation and now EVERYONE can understand me. Don't know if it would have bearing on your problem, but thought I would mention it. Bob may have some thoughts on this as a possible cause of your problem.

[SkyPirate]

that's a good post RobS ..CB radios use to have the same issue( some still do) and a potentiometer had to be adjusted in the mic curcuit to fix it,..makes sense to me