avionics static

[GMBrown]

This is probably insolvable by this group (as good as it is) without getting hands on, but its driving me nuts so I thought I would run it by y'all, and see if anything clicks.

I start up the 1980 K 231 and fire up the avionics and my old KY 197 radio has static  that is so annoying that the radio is unusable.  When its tuned to ATIS, no problem.  Works great. No static.  But when on a regular freq, when not actively receiving, the static is really bad.  It isnt something that can be squelch adjusted.  My other radio, the GNS 530 works great.

Next time I start up the bird, the 197 is great.  No static. but the static didnt go away, it now affects the 530.  Again, its not a squelch issue, it seems to me, since its a movable target.  Is this a ground issue?  antennae connection?

I'm guessing I need to take it to an avionics shop and start opening the check book, which I don't really have a problem with, just don't know of any good ones near by.  Riverside, California, if you have any recommendations. 

I should mention that the static is not too bad when I first turn on the radio, but as it warms up, it gets worse.

Any hints gratefully accepted. 

 

 

Edited October 15, 2021 by GMBrown
Additional info

[Vance Harral]

We've twice traced problems like this to loose ground connections on devices associated with audio (once it was a voice annunciator, another time a headset jack).  But only after chasing other hypothesis for weeks/months.

At the time, we too thought the problems only started after "warming up".  Turned out to have nothing to do with actual heat, and everything to do with it being worse once airborne and flying even in the lightest of turbulence and G loads.

Before you go to the shop, suggest you first wiggle all the headset jacks in the airplane to see if you can induce the problem, as well as any other audio devices you can lay hands on (re-seat radios in the stack, look under the panel and under the glare shield for loose grounds, etc.)

[Ragsf15e]

I’d also listen carefully through a mag check to see if you might be able to tell if it’s ignition noise?  Is it happening with the engine off?  Try pulling the field wire breaker or otherwise removing power from the alternator too just to see if that changes it.  I’ve definitely had loose plug wires make static.

[Vance Harral]

1 hour ago, Ragsf15e said:

Try pulling the field wire breaker or otherwise removing power from the alternator too just to see if that changes it.

I used to give this advice too, but then learned a painful lesson that just because pulling the field breaker changes the nature of the noise, that doesn't meant the problem is in the charging system.

When we were chasing our loose voice annunciator ground problem, pulling the field breaker did change the nature of the noise, even though the alternator, diode bridge, and voltage regulator were not the cause of the problem.  We wasted time and dollars removing, overhauling, and re-installing the alternator - which requires removing the lower cowl and is therefore a giant PITA - to no avail.  The problem remained, and even exhibited the same behavior of getting quieter and sometimes going away when the field breaker was pulled.  Only after finding and tightening the loose ground connection was the problem resolved. 

[GMBrown]

Thanks for the tips. I've got some things to check into.  That's what I was looking for. 

Garry

[GeeBee]

I've solved a lot of static problems on a lot of airplanes just by cleaning up the battery ground. Seems like if it is good enough to start the engine it is good enough right? Nope. 

 

 

[Ragsf15e]

3 hours ago, Vance Harral said:

I used to give this advice too, but then learned a painful lesson that just because pulling the field breaker changes the nature of the noise, that doesn't meant the problem is in the charging system.

When we were chasing our loose voice annunciator ground problem, pulling the field breaker did change the nature of the noise, even though the alternator, diode bridge, and voltage regulator were not the cause of the problem.  We wasted time and dollars removing, overhauling, and re-installing the alternator - which requires removing the lower cowl and is therefore a giant PITA - to no avail.  The problem remained, and even exhibited the same behavior of getting quieter and sometimes going away when the field breaker was pulled.  Only after finding and tightening the loose ground connection was the problem resolved. 

Yeah I agree it’s not a conclusive thing, but it might lead to looking closer at certain things, maybe narrow it down?  I also had a 2 year (and expensive) search for a low voltage problem (battery, alternator, vr, etc) which I eventually found was a slightly corroded connection.  I think the point for the OP is to try to narrow it down and test everything thoroughly because these are sometimes tough ones to nail - especially on the first try.