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Icom A200 Antenna Cable and intercom grounds

I’ll try pulling a temporary ground from the lights.

Random question - would a crappy dimmer introduce noise into the radio?

I replaced a dimmer that was super wonky. Lots of internal issues and barely functioned except at full bright. You could feel the internals grinding when you turned it

I didn’t materially change my music input at all during my wiring rework last night, but went to the hangar today to make sure it worked before a trip next week.

I noticed that the noise I heard before on the music circuit (I had assumed through the cigar lighter) was gone. But I didn’t process that until later this evening back home. I should have stuck the LEDs back in to see if they cleaned up as well.
 
Depends on the type of dimmer, but they can make noise.

Side note: music jacks need isolation washers, also, just like audio and mic jacks.

Web
 
Depends on the type of dimmer, but they can make noise.

Side note: music jacks need isolation washers, also, just like audio and mic jacks.

Web

I reused the existing music jack but changed the wires. This one doesn’t seem to have a good way to isolate the ring, but I’ll order a new one and replace it later.

On Sunday I’ll go give the led nav bulbs another shot just in case the old rheostat was passing noise into the airframe or something.

I really appreciate all your help!
 
On Sunday I’ll go give the led nav bulbs another shot just in case the old rheostat was passing noise into the airframe or something.

I really appreciate all your help!

Unfortunately I didn’t get a chance last week but I’ll try again tomorrow!
 
Unfortunately I didn’t get a chance last week but I’ll try again tomorrow!

Had limited time at the hangar so I prioritized my alternator over the LEDs. I'll give it a shot when we get back from vacation.
 
Today I swung by the hangar to get some measurements for another project and saw my neighbor was installing some G5's in his Cherokee. He's an EE for Boeing.

I showed him my nav light set-up and asked what he thought about the radio noise I was getting with those LEDs (also plugged them back up and verified it was still there). He agreed it was weird I was getting radio noise but said an inductor in-line with the nav light power wire would get rid of the noise. He's going to drop off a couple extras he has tomorrow and I'll install them when I get back from vacation.

I pulled the right wing nav light/strobe housing off, and the nav light has a single power wire and is grounded through the mounting screws. We shot the ground and it's good from the nav light housing screws to the battery ground (through the airframe). The strobe has a hot, ground, and signal (or sync?) all in a shielded wire. Right now that shielding's not bonded on either side, but I'm not getting any strobe noise in the radio or the ICS. I'm going to bond it though, more for general purpose than anything else.

I have a sinking feeling this is going to end up with rewiring the nav light circuit under the dash, since that's connected to the panel lights and the dimmer and all that. Maybe something funky is going on under there and that's what's causing a change from incandescent to LED nav lights to drop my radio reception like crazy? Either way, not looking forward to more time upside-down under the dash.
 
Bad call with the inductors. It's a band aid over a noise issue. Fix the source of the noise as that is the actual problem.

Have you pulled the bulbs to verify which one is making the noise? We're asking about the grounds as they can easily be a source of noise injected into the audio. Running a ground wire from the light to a ground point close to the battery will keep that current path separate from all others. THAT equals no noise. Until you figure out the exact source of the noise, any 'fixes' will be a shot in the dark, at best.

Only connect one end of the shield to ground. Connecting both ends can set up a ground loop (squeal in headset).

Web
 
Bad call with the inductors. It's a band aid over a noise issue. Fix the source of the noise as that is the actual problem.

I don’t want a band-aid, I’d rather fix it right if there’s a way to do that.

Have you pulled the bulbs to verify which one is making the noise?

I’ve got two sets of led position light bulbs, I’ve rotated them all through. One set has a bulb that’s worse than the others but the other set still effects radio reception.

We're asking about the grounds as they can easily be a source of noise injected into the audio. Running a ground wire from the light to a ground point close to the battery will keep that current path separate from all others. THAT equals no noise.

I haven’t done this yet. Trying to figure out the best way to snake a new wire through the wing and secure it. Looks like the original wiring was run before the wings were covered.

Until you figure out the exact source of the noise, any 'fixes' will be a shot in the dark, at best.

Agreed. I have tried running a ground from my antenna ground path directly to the battery ground with no effect from the LED bulbs interference. Haven’t done that from the bulb housing yet.

Does this problem seem unique to my airplane or is this more of a common issue?

Only connect one end of the shield to ground. Connecting both ends can set up a ground loop (squeal in headset).

Web

Will do. Thanks!
 
Have you tried a different brand of LED bulbs? When you pull the bulbs, one at a time, does the removal of one bulb stop the noise? If so, that bulb or that socket is the source of the noise. How about putting in the original bulbs? Not LED but no noise.

Web
 
Have you tried a different brand of LED bulbs? When you pull the bulbs, one at a time, does the removal of one bulb stop the noise? If so, that bulb or that socket is the source of the noise. How about putting in the original bulbs? Not LED but no noise.

Web

No, same brand but two different models of LED bulbs.

I’m pretty sure I pulled them individually and saw the noise in both wings with the “good” set of LEDs, but that was a couple of weeks ago and at 3am. I’ll run that test again this afternoon if I can get out of work a little early.

Original, incandescent bulbs make no noise. With an LED (same brand) in the tail I have just the faintest amount of noise. Imperceptible with the engine running.

The easy answer is to just slap the incandescent bulbs back in, which is what I’ve been doing. I was hoping the new antenna cable (which I would have replaced regardless) would have allowed these LEDs in the wings. I’ll keep trying to find and fix the noise source though, since I want it done right.

I really appreciate y’all’s help with troubleshooting tips and steps I’m missing!
 
Bad call with the inductors. It's a band aid over a noise issue. Fix the source of the noise as that is the actual problem.....

I agree that it's always best to fix the actual problem.
But if that proves problematic, what's wrong with a band-aid?
 
Because the problem is still there. Machines don't heal up. In fact they get worse as components wear. Cover up the noise and in time it will come back, usually because it gets worse.

Take this subject (noise on audio) and take it to an extreme. Starts out as noise in the headsets. If you cover it up with filters and inductors, the noise is still there, even if not audible. If the source of the noise puts out a stronger signal (think about alternators or magnetos) as they wear out, eventually the noise will become audible again as it exceeds the capability of the filter. If it gets even stronger, it will manifest itself as scratchy LED displays and flickering digital screens, etc.

'Band aids' get you out of a jamb. They buy you enough time to get the issue fixed correctly.

Web
 
Today I'll try to snag a video of the interference - that might help with pinpointing the source.

I'll also run a temp ground from the housing back to the battery ground for a quick check to see if that helps.
 
Temporary ground made no difference. I did get some video, but need to trim and upload them. I’ll do that after our bedtime routine with the little guy.

The great news is that I confirmed I have zero EMI with incandescent bulbs. In fact, I pulled the tail LED bulb and put an incandescent bulb back in there as well.

My hangar neighbor was working on installing some G5’s in his Cherokee, so I asked if I could use his plane to isolate the bulbs as the issue. His plane received the same radio interference as mine.

He’s going to take those LED bulbs to work and run them on a scope for curiosity’s sake, so I’ll report back with what he says if anyone is curious.

Other than the outcome of the LED bulbs, I think i can close out this project.
 
did you DISCONNECT the original airframe ground and replace it with a isolated ground back to battery?? or just add a wire??

The nav light is grounded through the housing, through the wing to the fuselage, so I pulled the housing out of the wing and ran an isolated ground back to the battery from the housing, outside the wing. No change.

I’m back to incandescent position lights and have zero interference.

Looking through the reviews on AC Spruce, it seems like I’m not the first person to experience radio interference with these bulbs. Plus they made identical interference on another airplane. I think the problem is effectively isolated to the bulbs. I’m pretty curious what they end up looking like on the O-scope!
 
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