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climbing to the top of a 1768-foot tall transmission tower
by Ken Alker 14 Feb '24

14 Feb '24

<https://www.ebaumsworld.com/videos/the-real-stairway-to-heaven/81100181/>

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Winter Field Day 2024 is this weekend
by Dave Schmidt 26 Jan '24

26 Jan '24

Saturday 11am until Sunday 11am Pacific time. Rules here: https://winterfieldday.org/downloads/2024-WFDA-Rules-Packet-V.-10.04.23.pdf " The designated Winter Field Day exchange is your call sign, your Class and Category, and your location identifier" For me it would be "AI6VX 1H SB" All bands acceptable except 12, 17, 30 and 60M. All modes except FT4 and FT8. Max 100W. Dave AI6VX

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Mesa Communications Site
by Levi C. Maaia, K6LCM 24 Jan '24

24 Jan '24

From Bill Talanian – Trustee Emeritus Equipment Shelter Relocation An emergency appeal is being sent out to all for assistance in finding a temporary no-cost rental home for the Club’s modular La Vigia equipment building (aka Talanian Communications Facility) on the Mesa in Santa Barbara. PHOTO ATTACHED. This is the result of a directive by the City of SB to remove our building in order to make way for the construction of a new underground water storage facility at that site. The physical location will be replaced by installation of two five million gallon underground storage tanks for drinking water. The time line for removal of our modular building is measured in days. We are investigating all potential facilities to store the modular structure until it may be eventually relocated to the La Cumbre Peak West site as timing and funding allow. With the help from many individuals we are looking at several possibilities. As soon as we can zero in on a location we shall need the funding for a crane lift service and flat bed truck. More info on the site: https://www.sbarc.org/2021/01/02/mesa-communications-facility-named-for-w1u… IF YOU HAVE ANY LEADS ON A POTENTIAL TEMPORARY STORAGE SITE, PLEASE LET US KNOW: https://www.sbarc.org/contact-us/ LCM Levi C. Maaia, K6LCM Director at Large | K6TZ Trustee Santa Barbara Amateur Radio Club Santa Barbara Wireless Foundation a 501(c)(3) nonprofit public benefit corporation www.levimaaia.com | www.k6lcm.com

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Steve Merchant - K6AW - silent key today
by Ken Alker 20 Jan '24

20 Jan '24

Steve Merchant (K6AW; and contest call of AK6W "100 Aker Wood Conteste Club") became a silent key at 4am at SB Cottage Hospital this morning. RIP OM 73, Ken KA6KEN

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FLP battery prices are expected to drop
by Dave Schmidt 18 Jan '24

18 Jan '24

Interesting read here: https://diysolarforum.com/threads/lfp-for-evs-projected-to-be-less-than-56-… Essentially due to battery factory over production and slow adoption of EVs. This would basically drop battery prices in half vs what we're paying now for LFP batteries. Hoping it happens! Dave AI6VX

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Fwd: [ARRLSB] Report via Marty Woll, N6VI from outgoing ARRL Vice-President Mike Raisbeck, W1TWF
by Ken Alker 11 Jan '24

11 Jan '24

From: "Kitchens, John, NS6X (SM, SB) via ARRLSB" <arrlsb(a)mailman.qth.net> To: arrlsb(a)groups.io Cc: "ARRL Santa Barbara Section" <arrlsb(a)mailman.qth.net> Sent: Wednesday, January 10, 2024 8:18:02 PM Subject: [ARRLSB] Report via Marty Woll, N6VI from outgoing ARRL Vice-President Mike Raisbeck, W1TWF ARRLSB - ARRL Santa Barbara Section Mailing List -------------------------------------------------------------------------- For your review: Date: Wed, 10 Jan 2024 12:44:54 -0800 From: "Marty Woll" <n6vi(a)socal.rr.com> To: "sccc" <sccc(a)contesting.com> Subject: [SCCC] Report of ARRL 1st VP Message-ID: <006801da4405$de22f890$9a68e9b0$(a)socal.rr.com> Content-Type: text/plain; charset="us-ascii" Hi, all. Here is some candid information from the outgoing ARRL First Vice President Mike Raisbeck K1TWF to give you what I consider an unbiased view of current ARRL Board issues. Mike has released this for public consumption. It is lengthy but is worth the read. Marty N6VI 1st Vice President Report to the Board January 2024 I've been the 1st VP for four years now, and a Vice-Director for twenty-three years before that - a quarter century in all. The truth of the matter is that for me the last four years have been quiet. COVID has had a lot to do with this - hamfests and similar gatherings are only now coming back into fashion. This inactivity has been a bit disappointing, but reality is what it is. In any case, this could well be my last 1st VP report, so I thought I would take up a few more pages than usual to lay out my thoughts, and to get some discussion going that might, in the long run, help lead the Board in some more fruitful directions. I have several concerns, all of them centering on matters of ethics and fairness. These are: - What is a not-for-profit and what does that mean for the way we conduct our affairs - The highly unethical nature of the "Shadow Board" - The meaning and importance of Board transparency - Equal representation for our members - Restructuring the Ethics and Election Committee I have also included some hints as to how these problems might be remedied. I. What it Means to be Not-for-profit We are NOT a for-profit organization, though considerations of long-term financial viability are hugely important. I applaud those who have been focusing on our finance-related problems and applying their substantial business experience. However, I repeat, we are NOT a for-profit organization. This difference between for-profit and not-for-profit organizations rests in the goals. To be for-profit defines the primary goal as optimizing financial payoff to stakeholders. There may be other goals, but they are secondary to generating ROI. In contrast, to be not-for-profit defines the primary goal as promoting a particular and generally non-monetary cause. Financial optimization is an important secondary goal, but it is only secondary. What does this mean for the League? It means that our primary focus is promoting Amateur Radio, the people who practice it, and above all, our members. Increasing interest in the hobby is something we all strive for, and I personally think we can make progress, even against the demographic tide that our ageing membership presents. But, contrary to the tenor of much Board conversation over the last few years, a shrinking membership will not kill the League. Membership has varied at different times in our history. It started at zero when the League was founded and has generally, though not universally, grown over the years. At every step, the League has adjusted to serve the membership it had. Shrinking membership is only an existential threat if we fail to manage the organization's size and scope appropriately. So, let's bring the panic level down a few notches. Let's continue to try to grow the hobby, and thereby League membership, but let's acknowledge that if we can't grow the membership, we can simply scale down a bit. The ROI in financial terms will be smaller, but that is secondary. The ROI in terms of supporting our members and our hobby will remain sound. II. The "Shadow Board" and its Ethical Ramifications As all of you are aware, we have, over the last two years or so, developed what I call a "Shadow Board." Those on the Shadow Board, roughly 10 Directors, apparently meet periodically to discuss Board matters, including proposed motions and actions. The remaining Directors are excluded along with the other Board officers. To the best of my knowledge, no formal reports or minutes of these meetings have been prepared, and certainly not shared with the rest of the Board. This is highly unethical, and highly damaging to the Board and to the League. Let me give some background information, then I will describe why this is unethical. First, I should describe my own board experience, which will give you an idea of where my views originate. I have been on several small and modest sized not-for-profit boards, including everything from the local radio club and a large charter school to the organization, FEMARA, that runs the New England Convention. I have also been on numerous municipal boards, both elected and appointed. A number of the League's Board members, past and present, have had similar experiences, and I believe some number of you also have experience on for-profit boards. I am most familiar with the municipal realm in Massachusetts, though I can assure you that the ethical and legal considerations are identical, or nearly so, in every state of the Union. Look up "Open Meeting Laws". In the government regulatory sphere there are very strong ethical and legal requirements surrounding the holding of unannounced or covert board meetings. In this context "meeting" generally means any gathering, physical or virtual (including some serial conversations), of a quorum of a board. If a town board were to be caught having shadow meetings such as our Board is doing, the participants would find themselves before a superior court judge and in very hot water within days and would be the subjects of state ethics commission investigations. So, what does this have to do with the board of a not-for-profit? First, let's consider why the rules for municipal boards are what they are. There is in the public sphere a general public right to know what the leaders are doing. This is critical if the public is to reasonably and rationally select, by election or through appointment by elected officials, those who would govern them. It is this purpose that leads to the demand for transparency, which I discuss later in this report. So how does this rationale apply to other boards, not-for-profit or otherwise? That depends on the nature of the board. For many not-for-profit organizations, perhaps it does not. Many, the majority I believe, of not-for-profit boards are self-selecting. The board members choose their peers and successors, often based on how deep their pockets are. There is no "public" in the same sense as the term applies to governmental boards. While in these cases cutting some board members out of board discussions may not be the best of governance practices, it does not necessarily damage the process by which the board is selected. This rationale applies as well to for-profit organizations with private or closed boards. The League does NOT have this kind of board. Directors are periodically elected by members based on geographic areas. Our model is very much like that of a governmental unit, a town, state, or country. Our members pay for their vote with their dues. And the geographic aspect makes it even more important to include every Board member fully in the decision-making process. Exclusion of any Director from discussions is, in effect, disenfranchising the members of their division. So how did this "shadow board" come to be? An underlying current has been the allegation of serious breaches of board confidentiality on the part of several Directors in the "out" group, and this has been given, implicitly and explicitly, as a reason for excluding some people. I have heard similar allegations aimed at Directors in the "in" group. But when I've asked those involved on either side to give me real details I must say, with perhaps one notable exception, that very little has been presented that would convince me we have a problem. Furthermore, to the extent that there have been breaches, how severe have they been? There are, to be sure, topics that demand Board confidentiality; personnel matters and certain business negotiations being at the top of the list, but the vast bulk of what we do is rather mundane, and assigning undue importance to confidentiality in these areas is largely an exercise in exaggerated self-importance. Our "shadow board" involves Directors elected by roughly two thirds of our membership. Conducting business as it does deprive one third of our membership of effective representation. Perhaps this is not illegal, although I'm sure that an enterprising attorney could construct a civil case that would at least get through the courthouse door. But it utterly fails the "smell test." It is wrong, it is unethical, it is harmful to the League and its membership, and it needs to stop. NOW. How might we protect the league from things like this in the future and make clear to our members that we take representing them seriously? I would propose something like this in the standing orders: "Whenever a quorum of the Directors meets, in person, virtually, or mixed, the meeting shall be announced to the entire Board and access to the meeting shall be given to all Directors, Vice Directors, and Officers." This is clear and concise but is far less onerous than the rules that apply to governmental entities. III. The Nature of Board Transparency One can and should infer from the previous sections that Board transparency is necessary for a healthy Board elected by the membership. It is, perhaps, not the kind of transparency that some critics of the League have called for, such as live broadcasts of Board meetings, though this argument could certainly be made. The point of transparency is that both League members and Board members should have sufficient information to carry out their roles. I see two areas in which our Board is lacking. First, our reporting of major actions is weak. The Board minutes that we feed to our membership seem designed to minimize disclosure to a fairly superficial level. Over the years we have intentionally avoided or minimized details of our deliberations; we have had specific discussion on this topic at Board meetings. Furthermore, we have been less than diligent in distributing what information we do reveal to our members in a timely fashion. In addition, we don't, as a matter of course, report who voted and how, unless someone requests a roll call, and when several Directors did start exercising this power more frequently, the Board voted to change the rules to make roll call votes more difficult. The rational as I understand it was that the roll calls were taking too much time. This is as specious an excuse as one could muster. In fact, why not record votes on every motion? The technology exists to do this easily and quickly, or it could simply be done by the Secretary. Reticence to record votes has far more to do with avoiding embarrassment on the part of the Directors than with saving time at the meetings. Can we do anything about this? Of course, and easily. I would propose adding something like the following to the Standing Orders: "All votes of the Board shall be recorded, including who voted and how, and, except in the case of votes made during executive sessions, immediately reported." This brings me back to the topic of Board confidentiality, already mentioned above in the previous section. Yes, there are certain things that should not be publicly disclosed, or should be disclosed only at a high level: personnel matters, legislative negotiation strategies, and certain sensitive business negotiations. There is good reason to be careful in these areas. However, such matters are generally easy to discern. Few of the cases of alleged breach of confidentiality that have come to my attention have had much impact in these arenas. So, what is the real reason for the Board's obsession with secrecy and confidentiality? As mentioned above, it is clearly the desire to avoid embarrassment (and perhaps even accountability?). This raises a HUGE RED FLAG. We've all experienced embarrassment and it isn't pleasant, but fear of embarrassment is also a very important signal that warns us when we are on a path that is ill advised, unethical, or worse, and that requires some serious rethinking. IV. Equal representation for all members We are a membership organization with an elected board. As such, each member's vote should be counted roughly equally. Sadly, and as we all know, this is far from the case. The following chart reveals the numbers of full members in each division as of last November with the relative value of a single member's vote in each division. The disparity is appalling. The vote of a member in the Southeastern division is worth one-fifth of that of a member in the Dakota division: Division Full Members Vote Value Relative to Average Atlantic 11464 0.8 Central 9306 1.0 Dakota 3052 3.0 Delta 6676 1.4 Great Lakes 11037 0.8 Hudson 4857 1.9 Midwest 5991 1.5 New England 8236 1.1 Northwest 11317 0.8 Pacific 8872 1.0 Roanoke 11693 0.8 Rocky Mountain 6990 1.3 Southeastern 14101 0.6 Southwestern 10655 0.8 West Gulf 11043 0.8 total full members 135290 average division 9019 There will never be perfection, as division membership numbers change over time. Nonetheless, considerations of fundamental fairness dictate that the League do something to level the playing field. Our members all pay the same dues; they deserve the same rights. The status quo is simply not defensible on ethical grounds. There are multiple possible solutions to this problem, all easy to describe but politically difficult to implement. But the problem must be solved. A good start would be to define boundary goals. Perhaps we should add something like this to our bylaws: "The number of members entitled to vote in each division shall be between 80% and 120% of the number in an average sized division." By this standard, only four divisions currently pass muster - Central, New England, Pacific, and Southwestern. V. The Ethics and Elections Committee The Board has for many years relied on an Ethics and Elections committee as a mechanism for managing questions of ethics and propriety. Any objective analysis of its efficacy would conclude that the results have been mixed at best. On smaller details having to do with the conduct of elections, the committee has mostly been able to bring order when needed. But on some of the truly important matters, the Committee has failed, leading to accusations of weaponization, arbitrariness, and bias. I will note three situations that have arisen in recent years to illustrate this. In one, a Director was censured for activities characterized as breach of confidentiality when, in fact, the underlying "offense" was an encounter between the Director and a Board Officer at a Board meeting, one that some Board members found to be unacceptable. The result has fueled anti-League rhetoric and damaged the reputation and stature of the Board. In another, a Vice-Director was denied the right to run based on an interpretation of conflict of interest that can, at best, be characterized as convoluted and tortured. Much to his credit, that Vice-Director took the long view and has since returned to the Board as an elected Director. An interesting side note is that a few years later, a Director candidate found himself in a very similar situation, and there was no action by the E&E. Inconsistent results like this damage the League. In the most recent, a Director proposed to publish a book that was in violation of any reasonable interpretation of conflict of interest. The E&E gave an initial OK, a decision that in itself was impossible to justify, then backtracked on that approval claiming that important information had been withheld, though the proposed publication would have been, with or without the withheld information and beyond any doubt whatever, a violation of conflict of interest. The result was a kerfuffle that cast the League in a most unfavorable light, and which gave the Director plenty of ammunition to criticize the Board. In summary, on big issues our Ethics and Elections committee has been an almost total flop. While it might be tempting to criticize the individual Directors on that committee, in fact, each of the three E&E committees involved in the cases above had a different membership. The problem would seem to have less to do with individuals than with a flawed process. One important flaw is that the committee makeup changes frequently due to our rules about who may serve on it. The short terms served on the committee have led to inconsistency from year to year, inconsistency that from the outside is perceived as arbitrariness. Another is that information and history do not seem to pass easily from one E&E to another. We keep trying to reinvent the wheel. One thing that is not a flaw is the various pieces of Board policy and Connecticut law that together form our code of conduct. While it is always a good idea to periodically review and update the code of conduct, the periodic attempts to "fix" the codification of the code amount to no more than rearranging the deck chairs on the Titanic, and doing so will not fix the problems with the E&E. Recent history shows that our problems lie not in the details of that code, but rather in the inconsistency of its application. Many boards of all sorts now call upon third-party organizations to vet ethical issues. We might be well advised to do this, as has been discussed several times in Board meetings. The following, framed as a bylaw change, is one way to proceed: "The President, or a committee appointed by the President, shall find and recommend an outside firm to investigate and adjudicate matters of Board ethics and election conduct." Another approach might be to enlist past Directors, Vice-Directors, and Officers, now presumably detached from the Board nitty-gritty but still familiar with the general operations, to take on this role. This would be less expensive and arguably would lead to an E&E better informed about board and election operation. "The Board shall elect an Ethics and Elections committee made up of 3 individuals who have served, but are not currently serving, as Director, Vice-Director, or Board Officer." VI. Summary In the previous sections I've laid out what I believe to be some of the most pressing issues challenging the Board today. To reiterate: - Balancing our not-for-profit character with the need for sound business management - The threat posed by the "Shadow Board" - Living up to our duty of transparency - Equal representation for our members - Fixing the Ethics and Election Committee process These are challenges not to the body of the League, but to its soul. Things like cash flow, building up an endowment, or increasing the membership are more practical problems, and we have on the Board and at the helm of the League people who are willing, able, and eager to tackle them. I've also sketched out possible solutions to the problems I've described. These would, of course, need to be fleshed out and made into motions, but that shouldn't be too hard to do. I would be happy to assist. VII. And Now for a Final It's time to wrap things up. I've been on this Board for 25 years now. It's been quite a ride. I've served under five presidents, survived no-code licensing, battled for antenna rights in the courts, fought in the "Vice-Director War", and gotten to know some very fine people in the process, many still with us, a few, sadly, no longer. I could try to name you all, but the list would be long, and I would no doubt omit someone important. But I will call out one old friend, no longer with us, whom I sorely miss. That would be Pacific Division Director Jim Tiemstra. Those who knew him may recognize some of his ideas in the preceding pages. I am not yet done with League service, but I may be entering something of a hiatus. For now, I'll be building up the veggie farm, finally putting my antenna farm back together, busying myself with town politics, sliding into professional retirement, and generally looking for new ways to get in trouble. 73, Mike Raisbeck k1twf 1st Vice President 72/73 John Kitchens, NS6X 805.216.2569 NS6X(a)arrl.org PO Box 178 Somis, CA 93066 ARRL Santa Barbara Section Manager ______________________________________________________________ ARRLSB mailing list Reply will go to Sender. Change TO to ARRLSB(a)mailman.qth.net to send to list. Section Website: http://ARRLSB.org List hosted by: http://www.qsl.net Administered by: NS6X mailto:NS6X@ARRL.net

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Winter Field Day Jan 27th and 28th
by Dave Schmidt 05 Jan '24

05 Jan '24

https://winterfieldday.org/ Good time to play with your radios! From the above website: What is WFD? Winter Field Day is a communications exercise. WFD is held on the last full weekend in January. WFD can be worked from the comfort of your home or in a remote location. You can participate by yourself or get your friends, family, or whole club involved. Winter Field Day is open to participants worldwide. Amateur radio operators may use frequencies on the HF, VHF, or UHF bands and are free to use any mode that can faithfully transmit the required exchange intact. Similar to the ARRL’s Field Day, bonus points are earned in several ways, including using non-commercial power sources, operating from remote locations, satellite contacts, and more. Dave AI6VX

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Re: [Digital] LED Light Drivers / Dimmers
by Levi C. Maaia - K6LCM 05 Jan '24

05 Jan '24

Sadly (for it) the dirty driver went out with the morning’s trash collection. No room for things in the shack that do their job poorly. I guess I should watch out myself! 😳 LCM *Levi C. Maaia, K6LCM* www.levimaaia.com On Thu, Jan 4, 2024 at 09:26 Ken Alker <ka6ken(a)alker.net> wrote: > 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"] > > > > > ------------------------------ > This email came from the SBARC Digital mailing list. > To unsubscribe, send an email to: digital+unsubscribe(a)sbarc.org > > New members can subscribe by sending an email to: > digital+subscribe(a)sbarc.org > >

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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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