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Big Noise on Bell 407 with two new KX165A


We have installed a lot of kx165A (8,33khz) on Agusta A109E & Bell 407. We had a problem with noise, on A109E we found the solution with the interlock pin, but on Bell 407 is impossible.

We probe with filters on Vicor converters, we change the vhf antenna location and when web think that the problem is ok. In two ir three days the problem come back.

We have the ‘R’ on display like a transmission with the noise.

Has somebody the same problem?

Muchamiel, Alicante (Spain), Spain

In the absence of comment from the avionics installers reading this how about something like this:

Shoreham EGKA, United Kingdom

Someone left their phone on!

Avionics geek.
Fairoaks. EGTF


I have exactly the same problem on Cessna172 with KX165A . When I set some frequency with 8.33 kHz, I hear noise in standby mode and “R” appears on screen for receiving, although there is no transmission from ATC Tower.
And this noise appears not from all stations with 8.33 kHz, but only from some of them. The noise is very disturbing.

Can anyone help, please?

I will appreciate your response.

Spilve (EVRS), Latvia

I have encountered exactly the same trouble on high frequencies (starting from 130.00) when mounting a new TRIG a few years ago. The problem had been solved by replacing the wires by double-shielded wires. Good luck !

LFLG - Grenoble le Versoud, France

Hi, Michel!

Thanks for advise!

What is double-shielded wire? Like on this picture?


Spilve (EVRS), Latvia

I think that picture is single shield only. RG400 would be double but beware that stuff is not very flexible so hard to work with:

@dima1967, this is double-shielded, but PVC insulation is unsuitable for aircraft.

LKBU (near Prague), Czech Republic

If you have a problem like @dima1967 (most likely is something is emitting spurious RF, and the radio is picking it up), is to start pulling breakers. If the noise goes away when you pull one of the breakers, you’ve just identified the culprit and you can start to work on rectifying the problem.

Andreas IOM
9 Posts
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