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Sudden Onset of Static in Headset

n74846

Well Known Member
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.
 
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.
 
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.
 
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.😝
 
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.
 
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).
 
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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
 
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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...
 
Have you tried a different headset?

I have a Lightspeed Sierra that on occasion does almost exactly what you describe. Loud pop then buzz/static. It goes away if I move the cord "just so" and will come back later when the cord shifts again. I normally use a different headset, and just haven't gotten around to getting that headset repaired/replaced.
 
I have tried a different headset through a different jack, but not visa versa. I'll add that to the to-do list for Friday. Thanks.
 
Is there someone in SoFL (within 100 mi. of LNA) who has the Garmin SL-40 installed in their panel, who would be willing to plug mine in and test fly? This will finally narrow down the issue to radio or plane. The shop suggested this to save me hours of them trouble shooting.

Please PM me if interested. Thanks!
 
Is there someone in SoFL (within 100 mi. of LNA) who has the Garmin SL-40 installed in their panel, who would be willing to plug mine in and test fly? This will finally narrow down the issue to radio or plane. The shop suggested this to save me hours of them trouble shooting.

Please PM me if interested. Thanks!

Why don't you borrow their SL40 and test fly it in YOUR Plane? A lot less work.

That's what I did when my Skyview Classic black screened on me after a software update. Borrowed someone elses for a few moments. Theirs booted up, mine didn't. Off to Dynon. Turns out the software update took out my hard drive.
 
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You are right, the easier way. But some may be concerned about putting their radio in a plane that might have an issue that might screw up their radio. All I need is a willing owner. Thanks for the input.
 
If you turned the radio off and you still get the static noise, as stated in your first post, how could it possibly be the radio at fault, when the radio is turned off, with no reception possible? Don't you have another device that controls the gain and the mute function, in line with the radio that also requires a possible battery replacement? I'm trying to follow the logic here.
 
Remove the radio completely from the picture. Disconnect the "9-pin Radio" D-Sub that is going from the radio to the "Main Board" (box with a ton of d-sub connectors going to it).

If the problem persists, then you've eliminated the radio completely.. and you're only left with (i think):
  1. The intercom unit itself (doubtful)
  2. The D-Sub connecting the intercom to the Main Board. (not seated fully, pin backed out of clamshell, etc. probably)
  3. Apparently there is a 1/8" audio plug going from the Mainboard via the "9-Pin GPS" d-sub to the "GPS Garmin 296-496" which is there in case you subscribe to XM Radio. That could be a source of noise as well if its dangling and touching something, broken wire, etc.
  4. Also two pins in the 37-pin "F PCB" connector on the Main Board go out to a standard 1/8" music input jack. That too could be a source of a problem if one of those wires broke free/dangling/etc.

But as far as audio.. thats it. I've seen those d-subs not get screwed in all the way, threads get cross threaded and you think its secured but its not, etc.

If the static is breaking the intercom's squelch, then its coming in on one of the pilot/copilot's mic lines. If not, then its coming in on the music input line to the intercom (which is actually the radio, XM receiver, and music input jack).
 
In the many things I have tried, I did leave out that I isolated TWO different sources of noise: The first is resolved with the radio off (the steady crackling), the second noise which occurs even with the radio off is eliminated by putting the intercom on isolate (the popping noise). So, I think the intercom is going, and still can't pin the other noise source. I did not build the plane and have limited skill in electronics.
 
In the many things I have tried, I did leave out that I isolated TWO different sources of noise: The first is resolved with the radio off (the steady crackling), the second noise which occurs even with the radio off is eliminated by putting the intercom on isolate (the popping noise). So, I think the intercom is going, and still can't pin the other noise source. I did not build the plane and have limited skill in electronics.

You can sometimes get noise from a ground loop if the insulation on the RG-8u antenna cable, gets brittle, check where it bends sharply at a 90 on the back of the avionics radio Tray. The CoAx cable would need replacing. It may look good, but inspect it carefully. Can't be too tight, nor too loose.

The other area is the intercom itself can just wear out, both volume controls and squelch controls can start acting funny, no longer acting in a linear fashion the pots might be going bad.
 
You may have checked this but, I suggest you check passenger side headset jacks. I believe there might be a failed isolation washer or a short in the wire to the passenger jack. This would explain why pilot isolate stops the noise. These jacks are hard to tighten and wires can be damaged if improper technique was used. Vibrations from flying can complete the failure. Good luck.
 
Yes. I took the plane to a small local radio shop. They opened the instrument bay and found a 1mm worn insulation spot in the intercom harness, which was occasionally grounding. They repaired it and most of the problem disappeared. I still had some scratchy static, so invested $100 for a new intercom based on forum suggestions. Everything finally cleared up and the SL40 is working like a champ.
 
I’m on my 3rd Flightcom 403. The first one had internal power transistor heatsink screw come loose and it shorted on the circuit board. I bought a used intercom to replace and it never did have good audio. I recently bought a new 403 and everything is hunky-dory….
 
I now have the same problem but I isolated it to the engine. Like yours it just showed up. On the ground at low RPM reception is static free, when airbourne with high RPM plenty of static. When reaching 1000' I pulled throttle to idle and 99% of static was gone, it followed the RPM. I checked the shielded leads and grounding clamp they were good. I have an external capacitor mounted to the firewall that the previous owner installed for this problem, its wired to the main electrical feed wire on the + side of the capacitor, replacing the capacitor has been the fix, it only seems to last around 2 years but is only $50 from Lockwood. I'm told the switch panel has a capacitor in it for this reason so I'm guessing it went bad some time ago.
 
Go to Lockwood's website, it's a blue capacitor. The previous owner installed it. There's one mounted inside the RV12 circuit board as well, however I'm still having trouble with static when I'm receiving a transmission, it seems to be caused by my voltage regulator, it follows the throttle but only occurs when the VR gets up to it's normal operating temperature. The problem is more common during the summer months not so much during winter months, I have moved the VR into the cockpit from engine compartment but still have the issue but only when it gets hot so now I'm replacing the RG58 coax to RG142 which is double braided. I've been doing a lot of TS and hopefully the new coax will stop the bleed over from the VR.
 
Yes I changed the coax and recommend it but not sure it did much.
I upgraded to VR to the latest Vans kit. It seems to be a good one.
 
A new discovery yesterday was the shield ground wires from the pilot and copilot headsets was disconnected from its butt splice. This was found inside the D sub connecter that goes to the Inter Com box. The connector splits in half and had the two White/Blk wires pulled out of the butt splice that goes to pin#1 for grounding, this was a good find, now to fix it and put everything back together, I did change the antenna coax, that was a lot of fun :-(
 
Solved the problem, I found the two wires (Wht/Blk)which are the shield grounds for the headset wires broke off at the butt splice. This connection is at the Intercom connector plug, it was under the shrink. I imagine that when stowing the wires prior to heat shrinking they got stressed and broke off and out from the butt splice. The wires from the head set do not go to the radio, they go to the intercom first. I also change the radio coax to RG142 which is double shielded. No more static on test flight!
 
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