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
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@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 _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
On 10/22/18 7:49 AM, Paul Andrews wrote:
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.
Can you tell us the makes and models of the offending lights? Maybe show pictures?
Our house is full of LEDs. While I have noise problems they seem to be coming from the usual culprits -- nearby switching supplies that I'm methodically finding and fixing or replacing. I don't seem see much coming from the lights.
With one exception -- when my wife turned on the lights in a room that isn't used much at the moment, I saw LF noise on my waterfall. Turns out that fixture contains a CFL that we haven't replaced with an LED yet. So our experience has been the opposite of yours, though I must point out that I've been looking mainly at LF through HF these days. I haven't done a systematic scan of VHF or UHF.
My understanding is that many LED bulbs use series strings of diodes with the current limited by the reactance of a capacitor. This seems like it ought to be quieter than the ~20 kHz AC inverter commonly used in CFLs.
Phil
My take on LED bulbs is that the conventional ones use a DC switching supply, but the ones with the new "orange filaments" which are actually strings of series LEDs that add up to about 90 volts and then I assume a resistor in the base (no switching?)
I dont think one can use a capacitor reactance to drop voltage reliably (without additional safety limiting devices) because the drop at 60 Hz might be fine, but the drop when a 1ms high joule transient comes along, the energy goes right through the capacitor and dumps all that transient into the LEDs with no protection...Just my theory, I have not proved it in practice. I do remember reports in the 60's when people were building their first LED clocks and using a small capacitor to sync to the 60 Hz line. That sooner or later, a high-rise transient would wipe out the clock?
just theorizing...
My understanding is that many LED bulbs use series strings of diodes
with the current limited by the reactance of a capacitor. This seems like it ought to be quieter than the ~20 kHz AC inverter commonly used in CFLs.
participants (3)
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Paul Andrews -
Phil Karn -
Robert Bruninga