Strobe noise question?

[Darinh]

This is a question for the strobes on my Kitfox...Tube and Fabric construction. I am asking this forum because you guys helped me a ton on my RV7 and seem to know a lot more than most others. Here is the problem.

I am getting a crackle or pop on my radio each time my strobes flash. This is a Nova 60W driver and it is mounted right behind the pilot seat. It is mounted on the tubing using adel clamps so it does cannot ground locally through the back of the case so I ran a 12 awg ground wire up to my ground buss behind the panel. After re-reading the grounding section on Aeroelectric, I see he has an avionics buss and a couple others. Is this a problem grounding my strobe power supply at the same place as my avionics? Should I ground them locally on the airframe tubing next to the supply? I should also mention that the power supply is only about 1 foot away from my comm cable but there is really not another place to locate it unless I put it in the wing tip. Any help or advise is appreciated.

 

[N941WR]

KitFoxes are cool, so no problem from my end. But then I also like and have flown T-Crafts, Cubs, Champs, & Luscombs.

When I set my strobe up in my -9 I did the same as you, the ground wire from the power pack and the shielding wires were run up to the common ground on the firewall. This turned them into very large antennas and like you, I could hear the discharge through the headsets.

The solution for me was to ground both right at the power pack. Easy enough to do on an RV. See if you can find a bolt or something close to your power pack that you can then make a steel washer with a tab that will allow you to ground it close to the unit.

The shielding wire from the strobe wires were also terminated with the power ground, right next to the power supply. The shield wire was cut off at the light and continued to the power supply with only that end grounded.

 

[Darinh]

Bill,

Thanks for the reply! I actually did a search and read that you had done this and thought I could also have the same problem. I will change the grounding location and hopefully that does the trick. At the risk of showing how much I don't know about electronics, why would the ground location make a difference? I somewhat understand the ground loop issue and was under the impression that the current flowing in a ground loop can effectively act as an antenna but can this happen with a single leg of the ground wire?

Do you think that having the power supply so close to the comm antenna cable is an issue? It is RG-400 cable and is obviously shielded.

 

[N941WR]

... why would the ground location make a difference? I somewhat understand the ground loop issue and was under the impression that the current flowing in a ground loop can effectively act as an antenna but can this happen with a single leg of the ground wire?

Do you think that having the power supply so close to the comm antenna cable is an issue? It is RG-400 cable and is obviously shielded.

As I understand it (and I'm an electronics flunky), what you have done is made the ground wires a really big antenna. By cutting it short, you remove this.