[amsat-bb] AMSAT: RFI from LED bulbs?

[Paul Andrews]

Bob,

RFI from LED lights has been a well-known problem in the VHF / UHF EME
(moonbounce) weak signal community for years.  The first generation of
LED lights were very strong RFI generators.  The most recent
generation of LED lights are much better but can still cause problems.
LED lighting RFI tends to be broadband noise and not visible birdies.

The best way to see LED lighting broadband noise is with an SDR and
waterfall display.  The SDR or radio AGC must be turned off.  It's
easy to find offending LED lights in your own home.  It gets trickier
finding RFI lighting and devices in neighbors homes.  Turn off all the
lights in your house and start turning them on - 1 at a time.  Watch
your noise floor.  RFI will be obvious.

The good news is that typical amateur satellite communications are not
really weak signal and low-level RFI is not usually a problem.
However, if you are trying to work satellite passes on the horizon,
LED noise can be an issue for high gain directional yagis with mast
mount preamps.

I have at least 100 RFI generating LED lights in a box in my basement.
I removed these from my home and my neighbors.  I have exchanged bad
LED lights for good LED lights.  My house is 100% incandescent and
fluorescent.  No LEDs as long as I'm operating EME on 144 and 432 MHz.
  LED noise does not reach up into 1296 MHz.

Good luck with your LED RFI issues.  They can be solved but it's a bit
of a "wack a mole" effort.

73 - Paul - W2HRO
















On Mon, Oct 22, 2018 at 9:25 AM Robert Bruninga <bruninga at usna.edu> wrote:
>
> I am hearing reports of RFI from these LED bulbs.  Not just HF, but also
> VHF.
> If you can make any quantitative assessments of such RFI, please let me
> know.
>
> And the amazing thing is that at VHF you will never notice it because RFI
> is noise power and it is noise power that keeps a squelch CLOSED.
> Manuallly open the squelch and sometimes RFI will show full scale on the S
> meter yet not open the squelch.  And on my radios, when the squelch is
> closed, the S meter is inactive and shows 0.
>
> Bob Bruninga, WB4APR
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