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-   -   Noise From Strobe System (https://vansairforce.net/community/showthread.php?t=172436)

Terry Lutz 06-15-2019 05:30 PM

Noise From Strobe System
 
I recently installed an LED strobe system, and I'm getting some radio noise. It sounds like "ssit-ssit-ssit-sist" each time the wingtip strobes flash (they flash in sync). The manufacturer suggested a 10uf capacitor be installed from the output of the switch to ground. That didn't help. The noise only occurs when there is an incoming transmission - it does not occur continuously when the strobes are on. For example, if I'm monitoring ATC, the noise only occurs when a transmission from ATC is received. Just wanted to know if anyone else has had a similar problem and found a solution.

rv7charlie 06-15-2019 08:04 PM

Only hearing the noise when the radio is receiving is a clue. Try opening the squelch on the radio & see if you hear it continuously. If so, that's a hint that the noise is getting in through the radio, but you still don't know if it's RF (being picked up by the antenna) or riding a ground into the radio's power supply.

Unfortunately, there's no universal cure; just some things to try.

Easiest 1st would be ensuring that the radio's antenna coax shield has high quality continuity from the radio all the way to the antenna, and the antenna ground has a good bond to the airframe.

Next would be trying the recommended filter, but at the LED module terminal(s) instead of the switch. In other words, a filter on each module.

Next would be the LED modules' ground paths. If the filters don't solve it, try a temporary ground wire (obviously, while the plane is on the ground) from each module back to the 'forest of tabs' near the battery. In other words, lift all the LEDs' local airframe grounds & run the grounds direct to the battery negative.

All the above are ways to chase ground path noise. If the LED modules are indeed radiating RF energy into the radio's antenna, that's going to be much harder to address.

rzbill 06-16-2019 05:27 AM

Are the strobes a single unit or are the 'power supplies' separate from the light assy?

Earlier in LED strobe development, RF broadcast noise was a common issue. If the power supply is separate, you can try building a Faraday cage around it. This is simply enclosing the power supply in metal that is grounded to the airframe.

I had similar issue with HID power supplies. I wrapped them in aluminum foil and grounded to the airframe. Noise gone.

Terry Lutz 06-16-2019 05:28 AM

Those are good thoughts, thanks!

WingsOnWheels 06-16-2019 06:43 AM

What brand strobes are they? Im not asking as a dig at the vendor, but for comparison purposes for others with the same brand. For example, I have aveo powerburst lights. They are using an airframe ground at the outboard wing rib. All power wires are run separate from all comm wires. I also have cheap automotive HID lights. I have no noise issues.

scrollF4 06-16-2019 07:24 AM

VAF Search is your friend
 
Terry,
Over the last decade, several quite-useful VAF threads have discussed this problem. Do a VAF search of threat titles using the words "LED noise" and simply "noise", kick back, and read the wisdom.

Sounds like you might benefit from the technique of grounding the LED power wire shielding at one end. That worked for my 7A (older AeroLED wingtip and tail lights...their newer models have virtually no noise). The VAF search will give you good info. In addition, check this out:
https://www.experimentalaircraft.inf...wer-ground.php

Hope these help.

Terry Lutz 06-16-2019 08:06 PM

The lighting system comes from AvioLights, a company in Poland that makes lighting systems for aircraft in Europe. http://aviolights.com/ The LEDs and their power supply are molded together in the light assembly itself. They have been open and supportive about trying to find a solution for the noise I'm experiencing. A complicating factor may be that I removed a Whelen system to install the LED system, and adapted the wiring used for the Whelen strobes. That may be part of the problem, so I'll need to review the wiring in more detail to see if there is anything I should do differently. I did do a search here for additional threads on this subject, and I'm still wading through all the commentary. Thanks in advance for your many suggestions - they are much appreciated.

rocketbob 06-16-2019 08:38 PM

There's a method to completely eliminate noise in switching regulators for LED landing lights using an additional adjustable DC/DC converter.

This was verified with a spectrum analyzer. As the LEDs were driven with the typical 13.8V supply the noise radiated back into the the supply. This noise or distortion is sort of like turning the volume up too high on your stereo.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Adjust for maximum brightness, minimum noise.

Pave Tim 06-16-2019 10:46 PM

Unrelated to the thread but Bob, your inbox is full trying send a message about XCOM radios.

Drop me a PM with some contact info!

Back to your normally scheduled programing.


Quote:

Originally Posted by rocketbob (Post 1353346)
There's a method to completely eliminate noise in switching regulators for LED landing lights using an additional adjustable DC/DC converter.

This was verified with a spectrum analyzer. As the LEDs were driven with the typical 13.8V supply the noise radiated back into the the supply. This noise or distortion is sort of like turning the volume up too high on your stereo.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Adjust for maximum brightness, minimum noise.


rocketbob 06-17-2019 06:52 AM

Quote:

Originally Posted by Pave Tim (Post 1353360)
Unrelated to the thread but Bob, your inbox is full trying send a message about XCOM radios.

Drop me a PM with some contact info!

Back to your normally scheduled programing.

email me rocketbob at gmail com

Terry Lutz 06-17-2019 07:36 PM

Flew today and adjusted the squelch as suggested. The noise is there all the time, not just during transmissions that break squelch. Then I received a note from Aviolights that a 10uf capacitor is far too small. They are recommending a 10mf capacitor to be installed just after the switch and then to ground. Hopefully, I can find one that isn't too large! Still working on the other really good suggestions, and sifting through other posts.


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