Interference between Z-Tron Labs landing light and ICOM A210 com - Advice needed!!

[Ron RV8]

I have two radios, a PS PAR100EX (combination radio / intercom) and an ICOM A210 com. I also have Z-tron Labs combination nav/strobes (no issues) and two Z-tron landing lights all hooked up adjacent to the fuselage for testing

The landing Lights are wired according to instructions with shields connected to ground wires at the power end only, then ganged to a single 16 ga ground wire which goes forward to a forest of tabs ground block on the firewall. The nav/strobes share the same ground wire... Coax shields are grounded only at the radio end.

The landing lights alone don't affect the PS, but it has an intermittent synchronous high whine when the wig-wag is turned on. The whine is not that loud and would probably not be noticeable when the engine is running... Increasing volume does not increase the whine... I can live with that...

On the ICOM however, the landing lights alone break the squelch very loudly, frequently and randomly unless squelch is set at maximum value. Squelch is normally set in the mid range and at maximum I am uncertain how usable the radio would be as it may take a very loud voice to open the mike... Even at maximum setting, it occasionally loudly breaks squelch for a second a couple of times a minute. That would be annoying... When the ICOM breaks squelch from the landing light, the RX light on the ICOM also comes on.

I had a friend over recently who is very good with electronics, but not specific to aircraft.

We tried strategically placing a few toroids on the power wires, but no change... We also went through the wiring, power, grounds and coax to try and identify if there was a problem there... We moved the antenna wires and shielded landing light wires apart as much as possible where they pass through the fuselage but noted no change. We switched antenna connections, no change... All of the grounds go to a "forest" on the firewall. I tried jumpering the landing light ground to a local chassis ground, no change... We disconnected the wires and tried powering and grounding the lights directly from an independent battery immediately beside the breaker panel to eliminate possible interference from the forward wiring runs, no change... We did enough experimentation to convince us that wiring and antenna were probably not the problem. It seems like the issue is RF related, but I am a rookie at this and am open to suggestion...

I am at the point of adding the front top skins to the fuselage, in order to fit the canopy, but I do not want do do so if I need to change some wiring.

Here are a few pictures of the installation...

This shows wiring in the breaker panel. The black sharpie indicates ground...

This shows the location of the landing lights plugged in just beside the fuselage for testing...

This shows the shielded (white) nav/strobe and landing light cables where they cross and exit the fuselage. Note that the coax (beige) cables come through the spar on the right of the photo, and the landing light, nav/strobe cables on the left. The only place they are close (about 2" apart) is where they cross the fuselage...

Warren at Z-tron did exchange the landing lights for a more recent version. This helped somewhat, bun unfortunately the problem persists. He is working on the issue and is willing to exchange again to see if it helps, or refund if necessary, but we are in Canada and exchanges through customs is not convenient to say the least.

My options seem to be:
- to wait and see what Z-tron comes up with
- to try another brand of LED landing light (Aeroleds) $$
- to try another brand of COM $$
- to get an avionics pro to look at my wiring (maybe $ for nothing)

I would really appreciate any advice more experienced members of the group might be able to offer. Are there filters or other solutions which might take care of this??

Thanks

 

[N941WR]

Try grounding them locally

I had the same issue with the same test when I was building and removed the stobes, landing lights, etc. from the forest of tabs and grounded everything locally.

Give that a try. Your mileage may vary.

 

[selhardt]

Comments about footwells

Noticed in the picture the belly antennas and wire routing in the passenger footwell area will be tight.

If you haven't, you might want to build the floor panel with the footwells for the rear passenger so you can see where everything will need to be when they are installed - gets very tight.

 

[molson309]

One thing to remember is that proximity makes a big difference. Right now it appears that you are testing with the lights hanging down fairly close to your radio antennas. When mounted in the wings (I assume you're going to mount them near the wing tips) you will have a) more aluminum between them and your radio antennas and b) they will be much further away.

That will change the profile quite a bit. My guess is that you are getting radiated noise from the lights that's getting into your antennas; I suppose you could disconnect the antennas from the radios at the radio end of the coax and see if it makes any difference; if it's coming in through the power connections this is unlikely to resolve the issue. Or, lengthen the power cables to the lights and place them approximately in the same place, relative to the fuselage, that they would be once mounted inside the wings. But remember that once they are mounted in the wings the wing structure itself will provide quite a bit of shielding to radiated noise.

Proximity of the wiring to the coax is probably not the issue - coaxial cable has very good shielding, on the order of 100DB or more. Disconnecting the coax from the antenna at the antenna end might also help you figure out how the noise is being coupled to the radios.

 

[Ron RV8]

Ztron Landing lights

Thanks for the replies guys...

Yes, the landing lights will go in the wingtips...

Thanks for the heads-up on congestion in the footwell area, I've looked at this before, as well as proximity to the aileron pushrod, but I've added a few wires so it's worth another look...

I will see if I can pull the ground pins at the plugs and jumper to an airframe ground, seems worth a try...

If that doesn't change it, I will make up my wing harness, and try moving the lights away from the antennas. Funny I thought about the parallel wiring, but not the fact that the antennas are very close... I'm working in a single car garage so unfortunately mounting the wings is not an option...

Regards