Static in ICS from LED strobes/Beacon?

[Steve Crewdog]

Good news: the radio worked.
Bad news: REALLY bad static whenever the strobes or beacon go off.

Avionics harness built by Faststack, strobes are AveoFlash LP, beacon is Aveo mini Red Baron beacon. Radio is GTR0200 with built-in ICS.
Landing lights work fine, no static on steady or wig-wag.

Aluminum aircraft, so everything goes to grounding busses, then to main battery.

Going to check the beacon and strobe grounds, any other ideas?

 

[BobTurner]

This is unfortunately not uncommon. And the cause(s) can be anything between subtle and outright voodoo. In no particular order:
1 Are all headphone and mike jacks insulated from the airframe, with a dedicated ground wire back to the GTR? Are the wires a twisted pair inside a shield (3 wires for stereo) with the shield grounded only at the gtr?
2.Are strobe power supplies insulated from the airframe, with a dedicated ground wire twisted with the dc power wire, all the way back to the on-off switch and ground buss? Ideally the twisted pair is inside a braided shield, with the shield grounded only at the switch end.
3. Is the avionics buss (voltage to the GTR) showing any drop when the strobe pulses on?
4. Try unplugging the antenna coax from the gtr. Any improvement?
5. Other stuff.

 

[Steve Crewdog]

This is unfortunately not uncommon. And the cause(s) can be anything between subtle and outright voodoo. In no particular order:

4. Try unplugging the antenna coax from the gtr. Any improvement?

I'll take #4 for $500, please, Bob. All goes away when antenna is unplugged. Will work more tomorrow when I have time.

While driving home.....
Let me think this through. The Comm antenna is attached/grounded to an aluminum fairing, which is screwed onto brackets mounted on a wooden root rib. So there is no connection from the fairing/brackets to the ground of the aircraft, and maybe the antenna is not grounded?... Maybe I need to ground the brackets, which will ground the antenna? Even though I'm getting good comm checks?

Called the wife, told her I'd be late for dinner, made a 180. Hooked up a jumper from the fairing to a ground stud, problem is still there. Dang!!!!

 

[BobTurner]

I'll take #4 for $500, please, Bob. All goes away when antenna is unplugged. Will work more tomorrow when I have time.

While driving home.....
Let me think this through. The Comm antenna is attached/grounded to an aluminum fairing, which is screwed onto brackets mounted on a wooden root rib. So there is no connection from the fairing/brackets to the ground of the aircraft, and maybe the antenna is not grounded?... Maybe I need to ground the brackets, which will ground the antenna? Even though I'm getting good comm checks?

Called the wife, told her I'd be late for dinner, made a 180. Hooked up a jumper from the fairing to a ground stud, problem is still there. Dang!!!!

As long as the aluminum fairing is a few feet in size, perpendicular to the antenna, electrically attached to the coax braid, it will function as a ‘ground plane’. No need for any connection to ground (other than the coax braid).

Check that the coax braid is making good connections at both ends. Check that the GTR has a solid ground connection to the ground buss. Pull the GTR, spray contact cleaner on all the pins, re-insert into its rack.

Does your coax pass close to the strobe wiring?

If your strobe or beacon wiring has any connectors, unplug them and then re-plug.(try to scrape off any corrosion)

 

[bjdecker]

Good news: the radio worked.
Bad news: REALLY bad static whenever the strobes or beacon go off.

Avionics harness built by Faststack, strobes are AveoFlash LP, beacon is Aveo mini Red Baron beacon. Radio is GTR0200 with built-in ICS.
Landing lights work fine, no static on steady or wig-wag.

Aluminum aircraft, so everything goes to grounding busses, then to main battery.

Going to check the beacon and strobe grounds, any other ideas?

Is this a "new" thing, or has it been happening since day one?

 

[Steve Crewdog]

Is this a "new" thing, or has it been happening since day one?

Since the first time I was able to hook the antennas up to the avionics.

 

[BobTurner]

Since the first time I was able to hook the antennas up to the avionics.

That’s useful info. Probably not a corroded connection then.

 

[bjdecker]

Are the headset and microphone jacks isolated?

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[bjdecker]

Also, how electrically "noisy" are the LED drivers (power supply) in the Aveo devices? It's pretty well understood and documented, that older LED devices (and cheaper ones too) would generate a LOT of RMI/EMI when operating due to the switching nature of the power supply (vs Linear) and the cost reductions that accountants like to force engineers to make ("Hey engineer, capacitors and resistors don't do anything and you've got an awful lot of them -- get rid of them...")

 

[Steve Crewdog]

Thanks for taking the time to answer, everyone. We're concentrating on getting the engine ready for it's first run, I was hoping it would be something simple so we could use the GTR for the first runs so this will go on the back burner. We'll still use the radio, but with the strobes and beacon off.

It will also be interesting to hear the noise when the engine is running. This may only be the tip of the iceberg, but I hope not!

 

[BobTurner]

. We'll still use the radio, but with the strobes and beacon off.

It will also be interesting to hear the noise when the engine is running. This may only be the tip of the iceberg, but I hope not!

Maybe you'll get lucky. I once saw an intercom that had a voltage regulator set to 13 volts. Engine off, there was a lot of noise as the regulator didn't have a high enough input voltage. Engine on, alternator at 14 volts, it worked fine.

Just a side note in case you worry about the FAA. A few years back they cited an owner for flying with his beacon off. The owner complained that it was not required for day time flying. The FAA cited the reg that if it was installed you had to use it (except for safety related stuff) all the time and if it wasn't working (in that case, it wasn't) then it had to be fixed before flight. The work around is to "uninstall it", whatever that means.

 

[Steve Crewdog]

Maybe you'll get lucky. I once saw an intercom that had a voltage regulator set to 13 volts. Engine off, there was a lot of noise as the regulator didn't have a high enough input voltage. Engine on, alternator at 14 volts, it worked fine.

Just a side note in case you worry about the FAA. A few years back they cited an owner for flying with his beacon off. The owner complained that it was not required for day time flying. The FAA cited the reg that if it was installed you had to use it (except for safety related stuff) all the time and if it wasn't working (in that case, it wasn't) then it had to be fixed before flight. The work around is to "uninstall it", whatever that means.

I guess I'll have to put a label on these marked "not installed" before the inspection....

 

[Carl Froehlich]

Also, how electrically "noisy" are the LED drivers (power supply) in the Aveo devices? It's pretty well understood and documented, that older LED devices (and cheaper ones too) would generate a LOT of RMI/EMI when operating due to the switching nature of the power supply (vs Linear) and the cost reductions that accountants like to force engineers to make ("Hey engineer, capacitors and resistors don't do anything and you've got an awful lot of them -- get rid of them...")

This.

On a previous build the wingtip LEDs were so bad it blanked out comms on the GTN-650. I added a backing plate on the opposite side of the fiberglass mount, grounded the NAV/Strobe to it with a short connection. Plane ground (from the firewall) was also connected here. This totally eliminated the RFI.

Carl

 

[Steve Crewdog]

Taking a break from working on the engine, simple troubleshooting question:

-the beacon and nav/strobes run to a bus bar on the wing root, then to the switches/grounds inside the wing/fuselage. I'm thinking about getting a piece of shielded wire and just running it directly to the switch/ground bus outside the aircraft as a test, bypassing the installed wiring. Almost like a jumper cable, if you will. Will let you know.

 

[BobTurner]

Taking a break from working on the engine, simple troubleshooting question:

-the beacon and nav/strobes run to a bus bar on the wing root, then to the switches/grounds inside the wing/fuselage. I'm thinking about getting a piece of shielded wire and just running it directly to the switch/ground bus outside the aircraft as a test, bypassing the installed wiring. Almost like a jumper cable, if you will. Will let you know.

I would first try post #13’s shielding. Mock it up with aluminum foil and alligator clips.

To help understand how difficult this problem can be: during my build I bench tested some cheap LED lights for possible internal lighting. I happened to have an FM radio playing. When I brought up the voltage on the lights the FM radio went nuts.

 

[Steve Crewdog]

I would first try post #13’s shielding. Mock it up with aluminum foil and alligator clips.

To help understand how difficult this problem can be: during my build I bench tested some cheap LED lights for possible internal lighting. I happened to have an FM radio playing. When I brought up the voltage on the lights the FM radio went nuts.

WOW!

Ok, the simplest one to try this on would be the beacon, since it is already on an aluminum sheet/fairing. If I read Carl's post correctly, I should/could tap another wire into the ground wire from the beacon and attach it to the nutplate for the beacon, then run a wire from the fairing to the ground bus?

"Electronics were rascals, and they lay awake nights trying to find some way to screw you during the day. You could not reason with them. They had a brain and intestines, but no heart."
Ernest K. Gann
The Black Watch, 1989.

 

[BobTurner]

WOW!

Ok, the simplest one to try this on would be the beacon, since it is already on an aluminum sheet/fairing. If I read Carl's post correctly, I should/could tap another wire into the ground wire from the beacon and attach it to the nutplate for the beacon, then run a wire from the fairing to the ground bus?

"Electronics were rascals, and they lay awake nights trying to find some way to screw you during the day. You could not reason with them. They had a brain and intestines, but no heart."
Ernest K. Gann
The Black Watch, 1989.

Just ground the aluminum plate to the beacon ground wire, which already runs back to the ground buss. The idea is to keep long runs of paired wires carrying equal but opposite currents, so radiated fields tend to cancel out.

 

[Steve Crewdog]

Just ground the aluminum plate to the beacon ground wire, which already runs back to the ground buss. The idea is to keep long runs of paired wires carrying equal but opposite currents, so radiated fields tend to cancel out.

Wilco. Thank you sir.

 

[Carl Froehlich]

Just ground the aluminum plate to the beacon ground wire, which already runs back to the ground buss. The idea is to keep long runs of paired wires carrying equal but opposite currents, so radiated fields tend to cancel out.

Keep the beacon (or NAV/Strobe) ground wire to the backing plate as short as possible. Attach ship ground to this saem point.

Carl

 

[moosepileit]

I was an early Grimes incandescent nav to LED bulb adopter. Local ground. Made a home run to forest of tabs at firewall- better. Stobes never made any noise.

Got a magnetic choke and ran the positive looped through it three times. Silence!

 

[Steve Crewdog]

Also, how electrically "noisy" are the LED drivers (power supply) in the Aveo devices? It's pretty well understood and documented, that older LED devices (and cheaper ones too) would generate a LOT of RMI/EMI when operating due to the switching nature of the power supply (vs Linear) and the cost reductions that accountants like to force engineers to make ("Hey engineer, capacitors and resistors don't do anything and you've got an awful lot of them -- get rid of them...")

I think Brian hit the nail on the head. A friend let me borrow his newer AVEO wing LEDs and beacon, just hooked them up to my system and.... silence. Just one initial static when the strobes are turned on and after that, nothing.


We still haven't ran the engine, and I'm also going to try running a test piece of shielded wire in place of the installed beacon wiring and use the old beacon, see if I can avoid buying all new lights and nutplates, but we're getting closer, I think.

Thanks, everyone.


fyi, these are the lights that are giving me the heartache. If anyone's interested in buying them plus a mini-Red Baron Beacon, I'm interested in cutting my losses.

 

[bjdecker]

I think Brian hit the nail on the head. A friend let me borrow his newer AVEO wing LEDs and beacon, just hooked them up to my system and.... silence. Just one initial static when the strobes are turned on and after that, nothing.


We still haven't ran the engine, and I'm also going to try running a test piece of shielded wire in place of the installed beacon wiring and use the old beacon, see if I can avoid buying all new lights and nutplates, but we're getting closer, I think.

Thanks, everyone.


fyi, these are the lights that are giving me the heartache. If anyone's interested in buying them plus a mini-Red Baron Beacon, I'm interested in cutting my losses.

Even a blind squirrel finds a nut every so often.