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Static on radio DESPERATE TO SOLVE

rkiefer2

Well Known Member
Hello,

I’ve got a factory built 2013 RV12 ULS with Dynon classic view, Garmin SL40 radio, Flight com 403 intercom, auto pilot, and ADSB.

PROBLEM: When radio is receiving I it get static with the radio call.

Intercom works great, my transmissions to others are clear. NO STATIC OTHER THEN WHEN I RECEIVE. I’ve spent about 10 hours checking wires, connections, turning off lights, turning off Dynon, off ELT, replaced intercom, had Garmin radio bench tested, reseated/sealed antenna, even took it to an avionics shop and spent $2000 for them to replace the coaxial cables with shielded ones. Also I did find initially a loose ground on the connector behind the tray, tightened, ALL NO HELP.

Everything worked good for about 4 hours and then the static returned with a radio call randomly and looks like it is here to stay.

I’m hitting a wall on this one and desperate for some help with a solution. Any ideas on what else I should do specifically or things to try?
 
You don't have a third-party/cheap USB power plug installed, do you? Asking just because those can cause a lot of noise sometimes. Is the static also present when the airplane is not running?
 
You might check antenna connection on back of radio tray for SL40. The 90 degree connector is fastened to the tray with two screws that can come loose – happened to me. To do thorough inspection, you need to remove instrument bay top sheet metal.
-
 

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COM antenna distance to GPS antenna.

If distance between COM / GPS-antenna is less than 3 ft, I would unplug
the GPS-antenna from the Dynon Classic just to check.
The GPS-antenna is DC powered.
A notch filter on the SL40 may help.

Good luck
 
Also, check the music input jack socket. That was the cause of static on our 12.

Agree with Greg - USB sockets can spew RF out unless you get a specific suppressed one. Don't need to be expensive, plenty of references on the forum.
 
was at wit's end

My radio (GTR200b) noise issue seemed to be only on transmit.
Pulled the Dynon screen to got behind the panel & check connections, took radio out for exam, pulled wings out to install new headset jack isolators.
After days of doing all that, I happened to crawl under the plane to visually checkout the bottom surfaces and noticed the com antenna didn't appear tight to fuselage.
Sure enough, the phillips head screws turned rather freely.
Opened inspection port, so as to hold nuts, and tightened the screws,
Voila ... perfect comm again.
Was focused on the front end had neglected to think about the "whole" system (ground plane interuptus)
 
Try using a handheld radio. If that receives static too, then you will know that
the static is coming through the air and not through wires.
 
Not just cheap USB sockets.

Those USB "power banks" are noisy too. Lots of folks who were running the homemade Stratux ADS-B receivers were powering them with really noisy "power banks". And, having problems with those power banks actually breaking squelch on their com radios.

If you have to have one in your airplane, buy the ones from Sporty's that are made to be low-noise.
 
I'll echo what everyone else said. Any DC-to-DC power supply (or a switching power supply) is very noisy. I'm not sure if the legacy RV-12 came with extra USB power ports mounted somewhere.

The fact that the intercom is OK, but the radio-receive is garbage, makes me quickly exclude the headset/wires/intercom. Based on what you said, sounds like the antenna and coax can be excluded too. The only thing that's really left are the speaker and mic wires between the radio and intercom, and the power to the radio, especially the -12v (ground) to the radio.
 
I have the same problem with static noise on the radio. Installed a new antenna and replaced the co-ax cable with RG-400. Noise is still there, however if I hold the antenna while receiving the noise goes away. By the way the noise is only on certain frequencies, not all of them.
 
Last year I had issues with my SL40 and sent it in to Garmin for service. Before using the repaired (circuit board replaced) unit the avionics shop wanted an SWR check done on the antenna to check the connection integrity between the radio and antenna. A young man, not very experienced with the equipment, put the SWR meter on the antenna and on the antenna cable under the fuselage. He checked through the frequency range and was looking at the meter for low readings. He had someone on the phone with him from their shop who was better versed with what they should be seeing and felt everything looked good to continue using. It’s been working well for almost a year now, and I don’t believe there was any issues with the antenna or cable when the radio developed the over modulation problem.

My point (finally) is when he was checking the different frequencies the meter would show different readings, and he said the radio did better at different frequency ranges than others. All were not equal and this was normal.
 
Also I did find initially a loose ground on the connector behind the tray, tightened, ALL NO HELP.

Everything worked good for about 4 hours and then the static returned with a radio call randomly and looks like it is here to stay.

^^^ This ^^^ Got me thinking;

Check the condition of the shoulder washers & isolation washers installed under the mic & phone jacks. If you don't know what they look like - here's a pic.

I had a similar "static" issue in my previous RV-7 that I built -- the shoulder washer had cracked and created a ground loop of sorts (moisture permeated the crack perhaps.).
 

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So is it static or breaking squelch?
There were some s/w updates that addressed the squelch issues.

Vic
 
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I strongly recommend everyone put an antenna analyzer on their antennas at the end of the feedline going to the radios. Do this during the build and anytime you change something or have a radio problem. This tells truth and is a much preferred shortcut to the typical “change stuff out at random” approach.

Side note: Using an analyzer is how you make a wingtip VOR/ILS antenna work to its full potential.

Here is a nice one that can be a shared tool for Airparks, EAA chapters and such. Find an Amateur Radio Operator that knows something other than digital comms to show you how to use it.
https://www.dxengineering.com/parts/mfj-259d

With the little information provided, I’d guess the antenna is not the issue but I’d start there anyway as it is dirt dimple to check with an analyzer. Instead this maybe standard RFI coming from someplace yet to be determined.

A simple tool to go search for RFI is a hand held radio with a little rubber duck antenna. Sit in the plane (with the plane outside the hangar) and listen to ADIS or such. Then change to a frequency not in use. Now with all breakers open shut your master switch(s) and listen to the change in noise on the handheld. Move the handheld around looking for a increase in noise (as in your are moving it around to see if anything changes as the handheld gets closer to stuff in the panel). Now bring the non-panel stuff up one breaker at a time and repeat. After that bring up the panel one breaker at a time and repeat. Hopefully you will find the culprit (unless it is the Garmin radio itself but even is so it might show up on your handheld).

Note - do not have any external power connected to the plane for these checks. If needed charge the battery(s) after you are done.

Let us know what you find out.
Carl
 
^^^ This ^^^ Got me thinking;

Check the condition of the shoulder washers & isolation washers installed under the mic & phone jacks. If you don't know what they look like - here's a pic.

I had a similar "static" issue in my previous RV-7 that I built -- the shoulder washer had cracked and created a ground loop of sorts (moisture permeated the crack perhaps.).

Had this exact problem on my 7 as well. Was very frustrating.
The jack nuts had just come loose
 
Thank you everyone for your input. I've read through all the replies and recommendations.

This saga continues for me. I built the below matrix of actions taken and the results in hopes it helps as a guide to solving the problem and/or helps someone in the future with the same or similar issue.

I will keep the below Google Sheet updated with the tried and current recommendations.

PLEASE COMMENT ON ANY ADDITONAL RECOMMENDATIONS....IM TROLLING THIS ON FORUM DAILY FOR SUPPORT.

https://docs.google.com/spreadsheets/d/1iNICyTTAEGfq_z71jvp-_5q32lNU9pDUcNLuzgcteS8/edit?usp=sharing
 
clean the antenna

... I began having radio receive issues with quite loud background static recently. I made a long list of troubleshooting steps, and then read here on VAF to make Step 1 cleaning the antenna. The suggestion was to REALLY clean it, Acetone/MEK etc, and then use a maroon Scotchbrite pad with light pressure to clean it more.

I never got to step 2 of my troubleshooting list as this solved it for me.

My 2 comm antennae are on the belly of my RV-8, and lay in the exhaust stream, which contributes to greasy/oily antenna. The theory is grounding issues with the contaminates on the antenna.
 
antenna - more options

As Clam noted, a solid, clean electrical bond on the antenna is important. If you have access to Alodine, that's a good treatment to achieve good electrical bonding. Also, the attach screws should be torqued appropriately (and evenly).

I had a similar problem with my '12 (poor performance, xmit and receive) I cut off the connector (the antenna side of the coax) and very carefully crimped a new one on. The orig crimp on the center pin looked "odd". Problem solved. My neighbor had a similar problem with his C150. Same fix worked for him.
Hope that helps!
 
Some thoughts:

- Antenna cleaning. Always a good first step. For belly mounted antennas exhaust gas plating out on the antenna base can establish an unwanted (and noisy) coupling between the radiating element and ground.
- Antenna ground. Required but don’t get carried away (as in scrapping paint off the fuselage). The antenna wants to have an RF ground, not a DC ground. Any practical thickness of paint under the antenna base is not a problem. I do suggest using star washers on the mounting screws.
- Connectors. Always a prime suspect. If you have not run out the antenna and feed line with a real antenna analyzer then the only practical way to find a bad connector is to do a simple conductivity check - then replace it anyway. Everyone is not proficient at installing crimp BNC connectors (at least the first few). Don’t forget to suspect the connector at the radio as well.

Carl
 
my A&P maintains a fleet of 5 LSA RV-12s.
3 have had the same issue andhe tracked it down to the mike ground.
Apparently the Garmin gtr200 mounting instructions call for it be grounded .
when he rewired the mike ground and grounded the gtr 200 as per garmin instructions the problem was fixed.
Alan
 
Is there a GPS396 or 496 installed with its audio output connected.
If so, it needs an audio isolation transformer aka ground loop isolator.
 
Hello,

I’ve got a factory built 2013 RV12 ULS with Dynon classic view, Garmin SL40 radio, Flight com 403 intercom, auto pilot, and ADSB.

PROBLEM: When radio is receiving I it get static with the radio call.

I've go the same setup in my RV-12. Same symptoms as you described. I found out the hard way that if you plug a mono headset into a stereo wired Flightcom 403 it will sound terrible and eventually cause permanent damage. I read that in a Flightcom 403 install manual at some point but the current 403 manual doesn't mention anything about damage. Maybe later versions are better behaved.

If you plug a mono headset into a stereo jack you are essentially shorting one audio output to ground via the mono plug. Not unreasonable, I suppose, that it might cause damage. Still, there are enough mono headsets around that it is kind of rude.

A new Flightcom 403 cured my extremely scratchy audio woes.
 
Hello,

I’ve got a factory built 2013 RV12 ULS with Dynon classic view, Garmin SL40 radio, Flight com 403 intercom, auto pilot, and ADSB.

PROBLEM: When radio is receiving I it get static with the radio call.

Intercom works great, my transmissions to others are clear. NO STATIC OTHER THEN WHEN I RECEIVE. I’ve spent about 10 hours checking wires, connections, turning off lights, turning off Dynon, off ELT, replaced intercom, had Garmin radio bench tested, reseated/sealed antenna, even took it to an avionics shop and spent $2000 for them to replace the coaxial cables with shielded ones. Also I did find initially a loose ground on the connector behind the tray, tightened, ALL NO HELP.

Everything worked good for about 4 hours and then the static returned with a radio call randomly and looks like it is here to stay.

I’m hitting a wall on this one and desperate for some help with a solution. Any ideas on what else I should do specifically or things to try?

You don't have a third-party/cheap USB power plug installed, do you? Asking just because those can cause a lot of noise sometimes. Is the static also present when the airplane is not running?

If there is no USB charger, make sure the radio is seated correctly. You will need an Allen wrench to make sure it is tight.
 
My Lightspeed Zulu 3. Has a dip switch setting for stereo and mono. Default is mono.
Check to see if your headset is configured ok for your system
 
Noise capacitor?

What about the noise capacitor/filter? I understand there may be a filter already installed on the circuit board? I know that Lockwood sells one for $60 that I believe goes between the voltage regulator and ground. I understand this is for similar issues.
 
I've had to do this as well, adding the additional capacitor from Lockwood, solved my problem. I understand there is one on the Vans circuit board, I guess it went out.
 
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