AeroLEDs Grounding for low RFI

[Dean_aeroleds]

All,

Here is some information that will help you to make sure your installation of AeroLEDs wing and tail lights do not create radio noise.

The key requirements are to follow the recommendation for using shielded wires, and to ground the case of the light to the black ground wire from the light within about a foot of the light.

The case ground for the wing lights can be done like this:


Note the ring terminal that grounds to the mounting screw and splices to the black ground wire on the light side of the connector. A similar thing should be done with the Suntail.

Please note that if you have the silver mounting bracket the anodization will need to be removed from the countersinks so the screw heads can ground the bracket. The gold mounting brackets are alodined so they are conductive.

The Suntail has a clear coating on the heat sink that also must be removed from the countersinks to allow the screw head to properly ground the body of the light.

Here is what the position light RF emissions look like if the body of the light is not grounded, or the chassis and power grounds run separately over a long run:


Note the peak around 120Mhz (right in the radio notch).

With the grounded done as recommended, this improves dramatically:


Likewise, here is the strobe for the ungrounded chassis:


Here is how it looks with the grounded done as recommended:


The step down in the limit lines for Cat M and Cat H are the levels that emissions need to be below to not be picked up by the radios. Cat M is the recommended level for most equipment, the extra margin of the Cat H line in the radio notch is for equipment mounted adjacent to a radio antenna.

I thought that showing these graphs would help make it more clear just how important following the grounding recommendations is for the lights to prevent radio noise. When the grounding is done per the above instructions, radio noise will be avoided.

Dean Wilkinson
CTO, AeroLEDs LLC

[jay.pearlman]

Dean,
Thanks for the inputs which are important - as you say. Can you put the picture in context? I do not know what you are showing.
Also, what are the impacts if the lights are in the wing tip along with archer antennae?

[johnfurey]

I have an Archer antenna in the tip and I have tried to follow eveything Dean has recommended to eliminate the strobe noise in my nav audio with no improvement regardless of how the grounds are arranged :

[NYTOM]

I'm doing my wiring now including installing my new AeroLeds. Although all those fancy graphs that I don't completely understand look great, that photo and description on how to ground are priceless. Thanks Dean.

[Dean_aeroleds]

OK, here is some help for the graphs:

Look at the part of the graph were the colored limit lines step down between 108 and 137 Mhz. This is the VHF airband that your Com and Nav radios use. If the black emissions plot is above the dark blue line in this band, that is a bad thing and you will hear noise on your radio from the lights. As you can see, when you don't ground per the recommendations, the lights create noise that is above the blue line. When you ground per the recommendations, the emissions are below the blue line. Every 3db is a doubling in signal intensity, so the 25db reduction in noise means that the noise signal amplitude is 256 times lower with the grounding than without.

Does that make the graphs more understandable?

[Dean_aeroleds]

John,

If you have the chassis ground from the mount connected to the black wire ground within 12 inches of the light, and have verified you have continuity from the set screw on the back of the light to the airframe ground, then there is another thing I can provide to help you. I can send you a set of filters that you can install in-line with the connector that will block anything from conducting down the wires. That could potentially help you with the proximity to the antenna. Send me an email at dean@aeroleds.com with your address, and I will work with you to try to fix your problem. Also, if you can email me photos of how you did your wiring that will help as well.

Thanks,

Dean

Originally Posted by johnfurey

I have an Archer antenna in the tip and I have tried to follow eveything Dean has recommended to eliminate the strobe noise in my nav audio with no improvement regardless of how the grounds are arranged :

[NYTOM]

Originally Posted by Dean_aeroleds

Does that make the graphs more understandable?

Yes Dean, it does. Thanks