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Re: LED Light Drivers / Dimmers
by Jay Hennigan 04 Jan '24

04 Jan '24

On 1/3/24 09:50, Levi C. Maaia, K6LCM wrote: > Anyway, I know that LED drivers can be a source of RF noise, especially > cheap ones that use PWM to dim the light from LEDs. The one that came > with this piece was visibly “dirty” to the point that I swear that I > could see the flicker at certain brightness settings. I put my portable > scope on the DC LED dimmer/driver output and it was very ugly. They are pretty much all PWM. Resistive dimmers are horribly inefficient. > I decided to do some research and see what I could learn about PWM and > LEDs. Turns out that the frequency at which these drivers pulse the > light varies from model to model with some pulsing the light on and off > at as slow a frequency as ~200 Hz. Apparently that was enough for be to > perceive flicker. I found another unit that was more that three times > faster (~600Hz) and swapped it in. The flicker went away and the picture > on the scope looks a lot cleaner now. > In the attached video I show the “clean" output, then the “dirty" > output. I can’t figure out how the dirty output manages to even dim the > light. It barely budges off of 12 volts while the clean driver has nice, > neat square pulses. The "dirty" one is likely just filtered with a capacitor across the output. LEDs are current driven. If the series LED string has a forward voltage drop of just under 12 volts and there's a fat capacitor across the output of the PWM dimmer it will look like 12 volts with a bit of ripple at the switching frequency on a scope. Ripple will be more evident at lower brightness levels. While you've labeled it "dirty" it's likely going to be cleaner from an RF standpoint than driving the LEDs with square waves over a length of wire that can and will act as an antenna. I suspect that the flicker is an artifact of the dimmer control circuitry missing pulses at certain brightness levels. Maybe poor line-side filtering causing power line "beating" with the internal oscillator at particular brightness levels. 200 hertz isn't going to produce visible flicker. Old-school TVs are 30 hertz with interlace that makes it effectively 60. 35-mm movies at theaters are/were 24 hertz, usually with a shutter that mimics 48 hertz to reduce flicker. Even many gaming monitors are 120 hertz or less. The fact that it only flickers at certain brightness levels says that the 200 hertz refresh rate isn't the cause of the flicker. > I didn’t notice any noise on the ham bands with either, which is good. I > have other LED drivers around the house that are noisier on the RF side. > Maybe I’ll try swapping those out. I think you'll find that the squarewave version is noisier. Try the low end of the AM broadcast band. -- Jay Hennigan - jay(a)west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV

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Re: [Digital] LED Light Drivers / Dimmers
by Ken Alker 04 Jan '24

04 Jan '24

As you imply, the 200Hz PWM waveform doesn't make sense unless at full brightness. I wonder if the scope lost trigger or something as you changed brightness during the 200Hz sweep (I do see that the frequency and time domain measurements change to "?" during the sweep, for what that is worth). The 200Hz waveform should look more like your 600Hz waveform; the average voltage needs to drop for the LEDs to dim so you gotta get back to a square wave. If the dirty one was the higher frequency, then I'd suspect the scope maybe wasn't catching the waveform (ie. too low bandwidth or too low of a sampling frequency), but that isn't he case here. (Maybe use a good 'ol analog scope?). --On Wednesday, January 3, 2024 9:50 AM -0800 "Levi C. Maaia, K6LCM" <k6lcm(a)maaia.com> wrote: > > Happy New Year! > > > For my December birthday this year, I received a cool LED "neon" > light. It is quite large so I have it hanging above my sofa in my shack. > The attached photo of it is a little weird looking. The blue doesn't > look like that in real life. I'll have to get another photo at night. > > > Anyway, I know that LED drivers can be a source of RF noise, especially > cheap ones that use PWM to dim the light from LEDs. The one that came > with this piece was visibly "dirty" to the point that I swear that I > could see the flicker at certain brightness settings. I put my portable > scope on the DC LED dimmer/driver output and it was very ugly. > > > I decided to do some research and see what I could learn about PWM and > LEDs. Turns out that the frequency at which these drivers pulse the light > varies from model to model with some pulsing the light on and off at as > slow a frequency as ~200 Hz. Apparently that was enough for be to > perceive flicker. I found another unit that was more that three times > faster (~600Hz) and swapped it in. The flicker went away and the picture > on the scope looks a lot cleaner now. > > > In the attached video I show the "clean" output, then the "dirty" > output. I can't figure out how the dirty output manages to even dim > the light. It barely budges off of 12 volts while the clean driver has > nice, neat square pulses. > > > I didn't notice any noise on the ham bands with either, which is good. > I have other LED drivers around the house that are noisier on the RF > side. Maybe I'll try swapping those out. > > > Here is another more detailed video I did a while back about tracking > down RF noise around the house. My kitchen LED uplighting is a continual > source of RF noise. > https://www.youtube.com/watch?v=keQmb2Maqes > > > LCM > > Levi C. Maaia, K6LCM > > www.levimaaia.com > > [Image: "uc"]

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Re: ARRL proposed By Law 46
by Levi C. Maaia - K6LCM 03 Jan '24

03 Jan '24

Even if this doesn’t pass, the league has serious leadership issues. I joined the RSGB To fill the intellectual vacuum that the league has left. RSGB still publishes a decent monthly journal, too. LCM *Levi C. Maaia, K6LCM* www.levimaaia.com On Wed, Jan 3, 2024 at 13:07 Ken Alker <ka6ken(a)alker.net> wrote: > The confidentiality ("Code of Conduct") language is apparently back again > for vote in a couple of weeks at ARRL! This look pretty serious - the > board is trying a second time. This got shot down a few years ago; there > was a lot of member protest. People are rallying the troops again. > > You can read about it here: > > Dec 2023: > 1) <http://lists.contesting.com/pipermail/sccc/2023-December/014575.html> > > After reading above, click link to right of "Next message" near the top to > scroll from one message to the next; there are 14 emails (Dec only), and > the Subject line (unfortunately) changes a couple of times, but if you > just > keep clicking, you'll see them all. When done with these 14, click next > link below. > > Jan 2024 > 2) <http://lists.contesting.com/pipermail/sccc/2024-January/014590.html> > > This is a continuation of the thread in January of this year, so far. > There > are 18 more emails as of today (again, several difference subjects, but > all > the same conversation). Just keep clicking next to "Next message" and you > can skip through the couple that aren't part of the thread. > > Ken > > _______________________________________________ > SBARC-list mailing list -- sbarc-list(a)lists.netlojix.com > To unsubscribe send an email to sbarc-list-leave(a)lists.netlojix.com >

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ARRL proposed By Law 46
by Ken Alker 03 Jan '24

03 Jan '24

The confidentiality ("Code of Conduct") language is apparently back again for vote in a couple of weeks at ARRL! This look pretty serious - the board is trying a second time. This got shot down a few years ago; there was a lot of member protest. People are rallying the troops again. You can read about it here: Dec 2023: 1) <http://lists.contesting.com/pipermail/sccc/2023-December/014575.html> After reading above, click link to right of "Next message" near the top to scroll from one message to the next; there are 14 emails (Dec only), and the Subject line (unfortunately) changes a couple of times, but if you just keep clicking, you'll see them all. When done with these 14, click next link below. Jan 2024 2) <http://lists.contesting.com/pipermail/sccc/2024-January/014590.html> This is a continuation of the thread in January of this year, so far. There are 18 more emails as of today (again, several difference subjects, but all the same conversation). Just keep clicking next to "Next message" and you can skip through the couple that aren't part of the thread. Ken

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Television Transmission via Laser
by WARREN MYERS 21 Dec '23

21 Dec '23

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Fwd: SANTA IS SOON TO FLY
by WARREN MYERS 08 Dec '23

08 Dec '23

> Some holiday DX fun, anyone? >> From: "Tedd Mirgliotta (KB8NW)" <kb8nw(a)barf80.nshore.org> >> Date: December 8, 2023 at 6:00:11 AM PST >> To: opdx(a)nshore.org >> Subject: SANTA IS SOON TO FLY >> >> >> >> >> FOR IMMEDIATE RELEASE, DEC.08.2023 >> >> >> >> CHRISTMAS 2023 WISHES FROM THE LAND OF SANTA CLAUS, FAR NORTH OF EUROPE >> >> Santa’s broadcasting arm, Santa Radio OF9X, will be active again, starting Monday, December 11, at 0000 UTC on all amateur radio bands and all modes; CW, SSB and FT8, and will be active till the end of the year, December 31, 2023, 21.59 UTC. The activity is organized by Radio Club of Pusula, OH9W and Radio Arcala, OH8X. >> >> The genuine Santa from Northern Finland, next to the North Pole, is about to start his journey to delight the world's children of all ages in all parts of our dear planet earth. Sadly, Christmas 2023 is different from the past as Santa will have to carefully navigate through the troubled parts of Europe and the Middle East, passing through partly closed air spaces. >> >> It's not only the elves that are busy preparing for the journey but also the hammerjacks at their radio stations. They will offer you a competitive spirit as we welcome you to greet Santa’s helpers on all band-modes and follow your personal progress on the OF9X Club Log leaderboard. So, who are these hammerjacks we speak of, and what is their role at OF9X? >> >> HAMMERJACKS? >> >> That is the puzzle you must decipher this year, right after we get Santa on his way! >> >> As a summary; Regardless of our turbulent times, the innocent children in their hopes for world peace and saving their planet are at the center of Santa’s mission every year – and 2023 makes no exception. >> >> You will have the following radio elves at the controls of the Santa’s virtual sleighs; Timo, OH1NX, Raimo, OH2BCI, Martti, OH2BH, Niko, OH2GEK, Arto, OH2KW, Erik, OH2LAK, Pekka, OH2TA, Pauli, OH5BQ, Anne, OH2YL, Jukka, OH2MA, Jorma, OH2KI, Jyri, OH2KM, Juha, OH2LQ, Henri, OH3JR, Risto, OH3UU, Tapani, OH5BM, Alex, OH5UY/UT5UY, Veijo, OH6KN, Mika, OH6NVC and Esa, OH8KTN. >> >> ---------------------------------------------------------------------------------------------------------------------------------------------------------------- >> >> Please see your progress on meeting the Santa on different band-modes: >> >> https://clublog.org/charts/?c=OF9X >> >> ---------------------------------------------------------------------------------------------------------------------------------------------------------------- >> >> >> >> >> >> >> >> >> >>

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Wiring A Continent : The U.S. Transcontinental Telegraph Line
by WARREN MYERS 23 Nov '23

23 Nov '23

Some interesting holiday reading on the history of the transcontinental telegraph. Happy Thanksgiving! http://www.telegraph-history.org/transcontinental-telegraph/index.html

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Solar Cycle 25 Update - Presentation by Carl, K9LA
by WARREN MYERS 15 Nov '23

15 Nov '23

Hello SBARC Attached is an interesting update on our current solar cycle, presented by a knowledgable DX operator of the Madison DX Club. Warren KN6ZZI https://www.youtube.com/channel/UCbOR4kFlf2JgMuGVx5pKNYg/videos Madison DX Club youtube.com

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Vintage Computer Fest SoCal
by Levi C. Maaia, K6LCM 15 Nov '23

15 Nov '23

Hi guys, I am passing along information about VCF SoCal, the first Vintage Computer Festival in Southern California. I attended VCF Southwest in Dallas and VCF West in the Bay Area last year and loved these events. It’s like a ham fest but for vintage computers. And there is a lot of crossover with vintage computers and vintage radios. Folks are using Commodore 64s and Apple Its to track the ISS and connect to Packet Radio systems and RTTY. It is very cool. People also bring things that could be museum pieces like vintage Soviet workstations and all-analog, vacuum tube computers as well as a ton of other tech from the 60s-90s. **See the photos attached.** I’m on the org committee and a sponsor for VCF SoCal. I’ll be exhibiting some stuff myself at the show down in OC this February. Check it out and consider coming down for it! https://www.vcfsocal.com/ LCM Levi C. Maaia, K6LCM www.levimaaia.com +1.805.604.5384

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Vandenberg launch in 5 mins
by Dave Schmidt 11 Nov '23

11 Nov '23

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