J

jchang10

Well Known Member
I decided to have a light show and watch the strobes light up. Then I thought, i wonder if there's interference with the radios.

Thus, with a handheld icom 24, sure enough, i get a click click click, on every strobe pulse. I got worried so powered up the panel radio.

Forunately, there is no clicking whatsoever with the panel mounted SL-30.

Now i am confused why the disparity? Is the SL-30 just superior at filtering out common "noises" like the strobe pulse? Or is a difference in antennas, or what?

Thanks,
Jae
 
Jae,

With radio frequencies, there is what is known as near field signals and far field signals. When you hold a hand held radio at point blank range, you pick up the near field signals. Near field signals don't necessarily propagate as far field signals.

Far field signals are true radio waves that are emitted by an antenna (intentional or unintentional antennas). Your airplane radio's antenna is likely mounted far enough away from the strobes that they don't pick up any near field signals, and the far field signals are low.

There is also the directional nature of RFI. If the device emits RFI in lobes that are stronger away from the airplane radio antenna and not so strong toward the airplane radio antenna, you won't pick them up with the panel mount as well as a hand held positioned away from the wing.

In the world of RFI test engineering, the joke is that everything is FM (fricking magic). Not entirely true, but chasing RFI problems can be maddening...

Dean Wilkinson
CTO, AeroLEDs LLC
 
Thanks Dean. I just tried locating the handheld near the belly mounted antenna, and i still get the click click click. Definitely still a mystery. However, i am duly impressed with the SL-30, at least compared with the Icom handheld. Even with a belly mounted antenna, it easily picks up radio calls that are more distant and more clearly than the handheld. I wouldn't be surprised if the SL-30 does some further FM (friggin magic) to filter some of those common pops and noises, as well.

Jae
 
Jae,

One difference between the handheld and the SL30 is the grounding. The SL-30 and its antenna are grounded to the same airframe as the strobes, while the handheld is floating. The SL-30 will reject common mode RFI while the handheld can't because it isn't grounded to the airframe.

Dean Wilkinson
CTO, AeroLEDs LLC
 
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