Noise filter

[Ron B.]

I'm building an RV-14A. Van's supplied a harness in the wings and also supplied (optional) the Aeroled Nav./Strobe. In their harness they used non-sheiled cable, so I ripped it out and installed 3 conductor shielded wire. Van's also supplied a noise filter to be mounted at the root of the left wing. Since I have eliminated the root plug and am using shielded cable I would like to install the filter at the location behind the panel where the three strobe wires (three strobes) join.
Any help in how I should add the filter or do I need one where I'm using shielded cable as per Aeroled. Aeroled shows no filter in their guide.
Thanks Ron

[RV3bpilot]

Some items you probably should not put a filter on like the strobe, it might take away from the amount of power going to the lights. Another is the transponder. But these items should always be in shielded wire. Most will even recommend a type of shielded wire or coax to be used.

I have put several noise filters in my aircraft. Mostly small capacitors at the source of the offending noise such as every electrical motor I put the capacitor across the positive and negative wires. Then every thing that produces a large voltage spikes like the strobes wires, tachometer wires, transponder wires are in shielded wires. I shielded the alternator wire and used large capacitors at each end.
Every wire that I'm trying to protect from noise I put in shielded wire, like temperature sensor, radio antenna wires, gps antenna wires, GPS RS 232 wires,

Then I tried to place noisy wires away from wires that I wanted to keep quiet.
Now everything is very quiet in my aircraft but only after much re-wiring was done.

Grounding is also very important. Try to use a single grounding point or grounding buss bar. Also I have read that to only ground one end of the shielded wire because if both ends are grounded there can me a small difference between the grounds and can cause noise by it self!
Good luck, Much patience is required for this type of work....

[Ron B.]

I'm using a forest of tabs for grounding and I'm like you most items only want the shield to be grounded at one but my Aeroleds call for grounding the shield at both ends of the run. Anyone know why?

[Mich48041]

Read THIS THREAD on the Matronics AeroElectric-List about the AeroLED shield. According to the poster,

Aero also now recommends using the Shield as the return ground to the main grounding point rather than a Local ground.

In the same thread, Bob Nuckolls (who wrote the book on aircraft wiring) explains the physics relating to shielding and electrical noise.
Anytime two circuits share the same conductor (airframe ground), the current in one circuit can affect the other circuit (create noise). Keeping the shared conductors short and using larger wire size between the instrument panel and battery will help to minimize the affect. Noisy electrical loads should not be grounded locally. Instead, they should use a separate ground wire connected to a common ground point like a forest of ground tabs on the firewall.

[Carl Froehlich]

Originally Posted by Ron B.

I'm building an RV-14A. Van's supplied a harness in the wings and also supplied (optional) the Aeroled Nav./Strobe. In their harness they used non-sheiled cable, so I ripped it out and installed 3 conductor shielded wire. Van's also supplied a noise filter to be mounted at the root of the left wing. Since I have eliminated the root plug and am using shielded cable I would like to install the filter at the location behind the panel where the three strobe wires (three strobes) join.
Any help in how I should add the filter or do I need one where I'm using shielded cable as per Aeroled. Aeroled shows no filter in their guide.
Thanks Ron

Ron,
The AEROLEDs are very nice units BUT you must install them in a specific way to preclude RFI from the units from getting into your radios. Cut and mount a piece of aluminum on the inside of the wingtip cut out such that the AEROLED mounting plate screws go through the fiberglass and into the aluminum plate (the plate is the same size as the bottom of the wintip cutout). On the unit wires, the ground wire gets cut as short as possible but still attaches to one of the three mounting screws. Attach your ground from your wire bundle to the same place.

The objective is a very short LED ground to the plate. I did this and in eliminated a significant RFI issue I had with these nav/strobes.

Carl

[Ron B.]

Thanks guys just the information I needed.