Sudden Onset of Static in Headset

n74846 · #1 06-27-2022, 04:45 PM

I am 10 hours since CI, a major job at Lockwood including new gear legs, 5-year hoses, and engine standoff. I mention this as a point of reference only. Today in flight the radio started crackling, popping and major static. I could not hear any transmission, AWOS, etc. I turned the radio off and still got the noise. I reset the headset plugs, but still no improvement. The VR is putting out the correct voltage/amps. When I slowed down in the traffic pattern the static mostly cleared and I could communicate.

I plan to check with the intercom off, examine all fuse pins, and recycle the master. Anyone ever have this event happen, or have ideas what to check beyond what I've outlined? I spoke to Lockwood and a local radio shop and have not gotten any definitive direction. Thanks for your help.

Mich48041 · #2 06-27-2022, 05:51 PM

Not saying this is the problem, but it won't hurt to check. Check the splice in the ignition wires forward of the firewall.
The center of the coax cables are spliced, but not the shields. Also check the spark plug wires.
Also check the AC component of the regulator output. Should be less than 0.5 volt AC.

Scott Hersha · #3 06-27-2022, 06:40 PM

Since the noise didn’t change with the radio turned off, I would be suspicious of your headset jacks, or possibly the headset plugs. Maybe something came off or got loose, like a ground wire or shield connection. Also, do you have one of those music input jacks? I had one in one of my prior airplanes and it did exactly what you described. There was something wrong with that music jack, which was wired through my audio panel and intercom system, and when I removed the jack, the noise stopped. Bluetooth music input has been trouble free.

Piper J3 · #4 06-27-2022, 07:23 PM

Look here.... https://vansairforce.net/community/s...d.php?t=184104

thiggins · #5 06-28-2022, 06:45 AM

This video talks about an interference issue with LEDs. I’ve experienced it myself.
Possible ?

https://youtu.be/S_5axPgnFns

RFSchaller · #6 06-28-2022, 08:57 PM

I have a legacy D180 avionics suite. I have noticed that if static occurs switching the ICS to pilot isolate kills it. Since I usually enjoy the social distancing of flying alone it is an easy solution.😝

n74846 · #7 06-29-2022, 04:32 PM

Thanks for all of the input. I did a couple of test flights today trying a number of your suggestions: Different headsets, different plugs, isolate the intercom, check the radio for secure mounting, and checking transmissions with a handheld. I'm still having the issue of good radio at departure with increasing static until unreadable. Today turning off the radio stopped the noise. The handheld (and tower) picked up static transmissions even when I was not transmitting. It has been suggested that a bad ground on the antenna might cause erroneous static transmissions. I've still got to search all wires later this week. I have an appointment with a radio shop in three weeks.

thiggins · #8 06-30-2022, 05:39 AM

That’s also exactly what can happen with a bad LED, the switching power supply causes the noise, even on your handheld. Try unplugging/powering off any LEDs you might have ( see the video in post #5).

lr172 · #9 06-30-2022, 06:49 AM

Quote:

Originally Posted by n74846

Thanks for all of the input. I did a couple of test flights today trying a number of your suggestions: Different headsets, different plugs, isolate the intercom, check the radio for secure mounting, and checking transmissions with a handheld. I'm still having the issue of good radio at departure with increasing static until unreadable. Today turning off the radio stopped the noise. The handheld (and tower) picked up static transmissions even when I was not transmitting. It has been suggested that a bad ground on the antenna might cause erroneous static transmissions. I've still got to search all wires later this week. I have an appointment with a radio shop in three weeks.

If both you and the tower are picking up static when you are not transmitting, that eliminates most of the classic stuff as it is not your system picking up errant noise (ground, LED, etc) and just putting it in the headset. That static is actually being transmitted from your aircraft with a decent amount of power. If the tower hears this with the radio off, that eliminates the radio as a source. If they only hear it with your radio on but not transmitting, it could be faulty and transmit noise even though the key is not pressed. May want to do some experiments in this area with the tower, as it is a weird type of problem. I think that a bad antenna ground would only create noise for the tower when that radio is transmitting. It should have no effect on the tower when not transmitting when all else is normal.

Do you have an ACK 121.5 ELT? I had a problem where I would pick up a loud screeching noise in the headset occasionally on final, but only on runways with ILS. Called around and found that ELT has a history of picking up certain transmissions and re-broadcasting them somehow. Pulled it's antenna off and sure enough it went away. Have no idea if the re-transmission was strong enough for the tower to pick up.

Sure seems odd that all is noise free on TO and increases in intensity as you climb. That also eliminates a lot of the classic static sources. Need to be thinking about what exactly is changing as you climb.

Larry

n74846 · #10 06-30-2022, 10:06 AM

As an update, I have a 406 ELT, Strobes are off, and no accessories in the 12v outlet. The radio shop suggested I put the battery on charger, turn on the radio with engine off and let it sit for an hour and see if I can reproduce the symptom. If it occurs it's the radio. If not, keep digging...