SV-COM and Strobe Pulses

jc2da

New Member
Joined
Dec 21, 2009
Messages
279
Ive been having an issue with the SV-COM since i got it a couple of months ago. Basically, it is picking up the strobe pulse and it comes out as a "click click" every time the tail light strobe pulses. It picks up the wing pulses, too but for some reason the tail light strobe gets the most audible click click.

It doesnt happen all the time. It appears to happen the loudest when listening to a quiet radio or when there is not another strong signal. The problem with a quiet channel is that the clicks trigger the squelch and so you are always getting click click and static. If you increase the squelch setting, then you will not pick up radio transmissions. Also, the volume of the clicks varies depending on the channel and other signals the radio is picking up. It is all very frustrating.

I have tried putting a 2200 uF capacitor across the power leads of the strobe pak - strobesnmore. All wiring to the strobes are shielded and terminated at the strobe pak. I tried wrapping aluminum foil over various things. I have tried moving the radio power and ground wires around. I have tried moving the com radio lines around. Nothing has worked.

The SL-30 does not pick up the clicks. There is a faint something, but barely audible. Im assuming the SL-30 does a better job at filtering clicks and pulses.

Basically, it seems to me that the SV-COM is doing too sensitive when there is no signal. You can hear the clicks get louder as it tries to pick up its signal. If you change the channel when receiving someone's chatter, the clicks disappear.

I am at a loss of what else to do. Any other suggestions? Could this be a defect i wonder?

Thanks
 

Raymo

I love aviation!
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Apr 25, 2016
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Richmond Hill, GA
I'd suspect the shielding ground at the tail strobe is not quite right. Also, confirm that the shielding is not grounded at both ends. You might try moving the shield ground from the tail to the closest ground point near the battery.

Since the SL-30 seems better, it might be antenna grounding related.
 

jc2da

New Member
Joined
Dec 21, 2009
Messages
279
hi Ray, thanks for the feedback. I will triple check those things again.

Do you have the SV-COM and you are fine? No pops or clicks at all with your strobe system? If nobody else is having this problem, then it is specific to me. Either a installation issue or some defect.

It still seems strange to how it varies depending on frequency and that the SL-30 is fine. If i tune 135.65 for instance, no noise whatsoever. Tune 127.0 to 127.30, pops and clicks. Actually, i should scan the entire range of frequencies. Maybe i can get more clues there.

http://www.vansairforce.com/community/showthread.php?t=116728
http://www.dogaviation.com/2014/08/installing-elusive-strobe-light-noise.html

These links also talk about how the RV-12 has a strobe noise filter capacitor, which is interesting.

Jae
 

jc2da

New Member
Joined
Dec 21, 2009
Messages
279
Here is another update. It is not specific to the SV-COM as the SL-30 is now doing it as well. In fact, a portable radio has the same clicks, too. I need to walk around some other airplanes with the portable radio and see if i get clicks.

I believe it is now specific to my new top mounted COM antenna. Unfortunately, using the portable radio, it seems everywhere that is top mounted gets clicks. Somehow i got lucky with the initial belly mounted antenna, as the clicks are less noticeable here.

Anyway, still chasing down possible solutions.
 

Raymo

I love aviation!
Joined
Apr 25, 2016
Messages
1,067
Location
Richmond Hill, GA
How is your tail strobe ground configured? Some MFGs, like AeroLED, used to specify grounding the shielding at both ends. You may find that moving the ground closer to the light helps or moving it closer to the engine works better.
 

jc2da

New Member
Joined
Dec 21, 2009
Messages
279
The tail shielding is grounded next to strobe power supply. I tried grounding further away and even onto the battery terminal itself. If i disconnect the ground, the shield is open circuit. Thus, it is not grounded at the strobe end. However, that would be another good test but would require quite a bit more work. The wiring gets rather crowded by the rudder end.

Strangely, if i move the strobe wiring around the power supply, the noise changes slightly. The clicks are still there, though, which is the main problem.

I have pretty much resolved that I need to change out the old strobes to the newer LED models. Unfortunately, it looks like they run about $400 to $500 a pop. This is the law of unintended consequences. Add a radio but have to spend double that to replace the strobes! :'(
 
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