If there’s anything more annoying to an amateur radio operator than noise, we’re not sure what it could be. We’re talking about radio frequency noise, of course, the random broadband emissions that threaten to make it almost impossible to work the bands and pick out weak signals. This man-made interference is known as “QRM” in ham parlance, and it has become almost intolerable of late, as poorly engineered switch-mode power supplies have become more common.
But hams love a technical challenge, so when a nasty case of QRM raised its ugly head, [Kevin Loughlin (KB9RLW)] fought back. With an unacceptable noise floor of S8, he went on a search for the guilty party, and in the simplest way possible — he started flipping circuit breakers. Sure, he could have pulled out something fancier like a TinySA spectrum analyzer, but with his HF rig on and blasting white noise, it was far easier to just work through the circuits one by one to narrow the source down. His noise problem went away with the living room breaker, which led to pulling plugs one by one until he located the culprit: a Roomba vacuum’s charging station.
Yes, this is a simple trick, but one that’s worth remembering as at least a first pass when QRM problems creep up. It probably won’t help if the source is coming from a neighbor’s house, but it’s a least worth a shot before going to more involved steps. As for remediation, [Kevin] opts to just unplug the Roomba when he wants to work the bands, but if you find that something like an Ethernet cable is causing your QRM issue, you might have to try different measures.
I was going to say on/off + binary search, but this sly fox is way ahead of me!
Every communication device these days using some sort of radio signal (WiFi,TV, mobile phone…etc) It’s one of those things that people not realise but technology not evolve as much as people think it did just been “upgraded”…
The FT817, ugh! 😮💨 The FT817 might be an egg-legging wool milk pig, but it’s not exactly very good at shortwave.
Except for PSK31 or FT-8 modes, were signal stability is more important than the rest.
Compared to an classic RF rig, like the FT-101, it’s deef and has poor modulation.
And it’s weak, too. It has less power than a tube era transceiver running off the driver tube. And worse large signal behavior.
For shortwave, I think, it should be nicknamed “FT-8-doesn’t work”. ;)
To be fair, though, the FT-857 unit was fine. It was the bigger brother and had meaningful output power level.
The 817 and 857 had a similar display.
That was it.
Even the reproduction tables where different. After Winelands mod on theb817 you have access to 220. Can’t be done on the 857.
“Switching PSUs and their interference are not an issue.”
They’re the root of all evil and I really mean it! :(
They deserve the title “one of the worst inventions of 20th century”.
Not only do they ruin RF spectrum worldwide,
but switching PSUs did end life of so many people, because switching PSUs dodn’t have galvanic insulation by design.
If they had, like with an transformer+linear regulator combo, then things like 50Hz/60Hz ripple and common mode interference wouldn’t make it to the DC side.
Seriously, a lot of people, including kids, haven been killed or injured by switching PSUs.
For example, when they were in the bath tub with a smartphone in their hands and had a charger cable connected to it.
Yes, it’s dumb to do. But Normally that’s harmless – IF the power supplies/chargers were still being bog standard linear PSUs from the 90s (the chubby bricks)!
Unfortunately, USB phone chargers do use cheap switching PSUs that are “hot” and have 50/60 Hz ripple on the DC side.
Enough voltage (90v) and Hz to make a human heart fail.
Switching PSUs are bad by design (they’re RF jammers) until fixed by adding lots of filters.
Expensive filters only lab PSUs will ever see!
That’s in total reverse to ancient linear power supplies,
which are clean by design but a larger and a bit more expensive to build.
SMPSUs do have galvanic isolation ‘by design’, they are safe to use and can be RF friendly if they’re designed and built properly, the problem, as has always been the case, is with cheap, corner cutting electronics which are badly designed and built, I’ve worked with consumer electronics for 40 years and cheap crap is not a new problem, it’s just more common now because of the likes of Amazon who allow anyone to sell any old garbage worldwide.
An interesting anecdote, years ago I worked as an electronics repair tech and one of our customers was a household name importer of electronics ‘fancy goods’ and jumped on lots of rising trends (even created a few), one of which was CB radio, they sent us crates of radios and assorted accessories to repair, one crate contained linear PSUs, about 150 of them.
A few used the LM723 or a quad op-amp but most of the PSUs in that crate used a 7812 with a few diodes on the ground leg to jack up the output and drive a 2N3055.
They had various trivial faults but the circuit was so badly designed and built that in about half a dozen of them the regulator was oscillating in the low VHF range and was wiping out the broadcast FM radio we listened to in our workshop.
The fix was simple, we swapped out the 7812 regulators for a different brand and added a couple of extra caps across input/output which stopped it oscillating but ‘by design’ they were far from clean.
Maybe that’s the truth, but I’m afraid you’re subconsciously making up excuses here because you’re pro-switching PSU and can’t handle the thought that the technology you support is so fundamentally flawed. No offense, though, it’s not meant personal.
I think that happens to same type of people who say that flying via plane is safe, despite horrible plane crashs are being happening year after year.
Ok, the oscillating linear PSU was a black sheep for sure, but not the norm, I think. Also, CBers often modify (ruin) their stuff, so most things that were in touch with CBers for a short moment are generally broken.
By contrast, 90 to 99% of todays switching PSUs are probably cheap smartphone chargers without any (meaningful) filtering.
Same goes for switching PSUs used in flat screen TVs, printers, laptop chargers and router PSUs. They radiate.
With PC PSUs being an exception here, since they are built similar to lab PSUs.
” 90 to 99% of todays switching PSUs are probably cheap smartphone chargers”
90 to 99% of any era’s stuff are cheap garbage.
“Ok, the oscillating linear PSU was a black sheep for sure, but not the norm, I think.”
Older linear supplies have the lovely feature of being unable to regulate without a minimum load, which can lead to absolutely wonderful turnon transients that can make things go ‘poof’. I think most hobbyists have experienced plugging in a brick, checking it with your voltmeter and going “holy hell.”
“With PC PSUs being an exception here, since they are built similar to lab PSUs.”
First: most “lab PSUs” are linear. Why the heck do you think they weigh a billion pounds? Huge transformers and gigantic heatsinks.
Second: a switching PSU in a generic PC is generally significantly worse in terms of EMI than a decent Delta brick supply (which is what like practically, all laptop bricks are). Generally, higher efficiency PC supplies are quieter up to a point. This may seem backwards because at very high efficiency EMI/efficiency fight against each other, since fast switch = less energy lost in the pass transistor, but cheap supplies just ram the switches on/off and the energy just gets lost in the ringing.
I’ve literally tested both in an anechoic chamber. It’s not particularly close. Laptop bricks aren’t actually far off from mil-spec style open-frame regulators. A lot of this is just a consequence of size: PC supplies are huge, they’re often just 2-layer PCBs with no attempt at shielding or damping switch nodes.
Third: building a quiet switching supply for a known load isn’t hard, it’s just hard to do it for a variety of loads. It has nothing to do with “expensive output filters,” it’s all in damping/confining the switch node’s ring. If you know the load, you can critically damp the switches.
Slapping a huge output filter on an SMPS is what you do when your design fails EMI and you’re trying to find bandaids.
Flying via plane is not safe? You must live in an alternate universe, my friend.
I challenge you to find data that makes flying look dangerous.
Completely ignoring how much smaller, more powerful and more efficient they are. Let’s blame the stupid people on the technology instead of them essentially bathing with a toaster.
No, I didn’t ignore it. I’m fully aware of this.
I was expecting such an low IQ comment, as well.
In my opinion there is no healthy cost-benefit ratio.
The RF spectrum is a world heritage and “holy”.
Polluting it and wantonly endangering people’s health in favor of efficiency is like sharing sewer lines with fresh water because it is “more efficient.”
Dude, you are clueless.
We, amateur radio operators, design and build switch mode stuff on the daily.
My homebrew AM transmitter. Totally PWM / switchmode. Running at 100 khz.
Also built a 2kv switcher. No issues.
Just because you buy the absolute cheapest garbage out there doesn’t make the tech bad.
You just bought garbage.
Kind of like buying a pyramid supply and expecting B&K Precision quality.
Just because YOU can’t do it doesn’t mean it can’t be done. Hundreds to thousands of people are running homegrown switch mode supplies with rf transmitters.
I could blow you away with my pulse width modulated amplifier (EER for the uninitiated) that gets better than 85npercent efficiently from 1 watt to legal limit, but I doubt you would get it.
Its impressively bold of you to call a comment low IQ while posting the lowest IQ stuff here.
Bathing with a toaster is probably safer, because it triggers an RCD.
The cruel thing about switching PSUs is exactly that the AC leak isn’t being registered by fuses and RCDs.
Naturally, people who’re using 5v DC cables expect them to be as safe as a bunch of AA batteries.
Or as safe as a Gameboy charger from their youth.
No one tells them about the danger. I wished EU would require PSUs to have a warning message on the supplied instruction leaflet.
Ignorance or intentional misinformation. I dunno.
IEC62368, and the previous IEC 60950 series, have ‘ground’ leakage limits, and require di-electric withstand as part of factory production. I have never used a SMPS that had over 2.4mA leakage or was not rated for at least 3000V withstand. They all had galvanic isolation provided by a hi-freq transformer that met di-electric, leakage, creepage, and clearance requirements for the scoped safety standards.
As for EMC, The thousands of SMPS that I have tested met the scoped CISPR and FCC limits. Well-designed linear PS will have less emissions than the equivalently power SMPS, its only advantage. Conversely a linear PS, for the equivalent power rating are too big, too heavy, too inefficient, too hot, and too susceptible (poor immunity) to TVS.
As for EMC, most problems result from poor end-user design, implementation, and integration.
“The cruel thing about switching PSUs is exactly that the AC leak isn’t being registered by fuses and RCDs.”
The only way an RCD won’t trip with current going through someone’s heart is if a person’s touching a source and its return with opposite hands. There’s no difference with switching, linear, straight AC, whatever. And if that’s true, you don’t need to be in a bathroom. It’ll happen in tons of situations.
And if you’ve got a live exposed source and return there’s always a possibility of serious injury regardless of the regulator type. You’re arguing against crap safety design, not regulator design.
“killed or injured by switching PSUs.
For example, when they were in the bath tub with a smartphone in their hands and had a charger cable connected to it.”
Ahhh…. thank you for the suggestion! .. now to rid myself of the old battle-axe, er.. I mean wife….lol …
Seriously though – “by code” most outlets in bathrooms “should” have GFCI protection.
Ergo, ‘in theory’, it “should” prevent electrocution hazards.
Ok, you obviously have no clue what you are talking about. A standard compliant switching PSU is perfectly safe and will definitely not kill anyone.
It’s only the super cheap —unapproved anywhere— chinesium dropper capacitor USB PSUs that can kill you on touch (about 50% of the time, depending on where the live connection eds up being…)
This is not correct at all. Cheap badly designed SMPSUs, yes maybe, but any properly approved one will be isolated.
Die eierlegende Wollmilchsau, richtig?
Noise affects all communication modes. It destroys your BER .
Wow this turned into a weird flame war. I will say that I got involved with (trying) to get some video game cabinets field UL listed, and yeah many of the suspiciously lightweight MeenWhale knockoff switching PSUs were leaky and wouldn’t pass. Replaced them with Meanwells and everyone got passing grades. So no, they’re not all created equally, and what you get on Amazon is automatically suspicious until proven otherwise.
And as for QRM, my house is FULL of switchmode supplies, but I managed to get lucky by accident I guess.. not one of them gives me any serious trouble on any band, except my 3D printer which is only used intermittently and my POE cameras, but I can filter that stuff with a notch on the radio, so.. no big whoop. Also, having the right balun on the antenna helps for some reason.
I just don’t feel they’re worthy of all the shade people are throwing. Yeah some are garbage, and there are lots of good reasons to get rid of those ones, so by all means, send them away. But to dismiss them as a class altogether seems silly.
Now for my radio, I definitely have a linear supply, because in theory they’re quieter, but mostly I realize because it looked badass with the big analog meters and was sitting next to the radio I bought and it was on sale. But I think a switcher would have been fine.
It’s hard to separate the supply from the electronics, too. It’s not like you get “super-well designed ultra-quiet electronics” coupled with “super-cheap switching supply” all that often.
We do some RF testing in our lab that’s at thermal noise levels (handy having an anechoic chamber 15 feet from your office to get down to -174 dBm/Hz) – most of the time the stuff that’s garbage is bad with its original supply and straight DC.
You also have supplies which in and of themselves aren’t that bad, but aren’t good at dealing with the typical crap on an AC line (their input filtering sucks): feed the DC they are providing into the anechoic chamber (from outside AC) and they’re terrible, run them off the filtered AC inside the chamber and they clean up a ton.
US hams are not allowed to use spread spectrum on any bands below 1.25m (222MHz). There is not enough room in the bands.
While I don’t believe frequency hopping is explicitly named within the Part97 rules that US hams must abide by, I suspect that it would run afoul of the “must not be used to obscure meaning” rules.
No idea how other countries have their rules written, but at least in the US, FHSS is not compatible with HF or VHF bands.
Only a complete idiot would think that excessive spectrum noise is a problem only for ham radio operators.
Thanks for the kind words, y’all baiting in a bait thread.
Like I said …
“The real problem is HAMs stubbornly sticking to communication methods of 1920s.”
It doesn’t sound like you’re familiar with the ham bands. That’s infeasible for anything with long distance propagation, which is what brought me to ham radio.
hello mr obvious.
I, for one, welcome the knowledge & experience of Mr Obvious.
Back when I was about 10, I started listening to shortwave radio. I was often frustrated by wideband hash noise. One day I was listening and heard the noise start right as the living room lights across the street went on. The noise changed as the lights dimmed. I went over the next day and explained what was happening. I threw a wire up into the trees and tuned in a VoA broadcast from Europe and then had him turn the light on. He was astonished! I offered to replace his ancient dimmer with a new one. (Yeah, I was a weird kid, I actually rode to radio shack and bought a dimmer with my own $.) I added a 22pf cap across the dimmer when I installed it. I had done that to all the dimmers in my house after discovering that this got rid of the last of the noise even a good residential grade dimmer made. That got rid of a huge noise source and made my listening a lot less frustrating. I checked the rest of the dimmers in his house, but none of them were even close to that living room in noise contribution. Unfortunately it seems that today even very expensive devices have some very poorly designed power supplies. The power supply for my CPAP caused so much interference that I almost had to stay up all night for my granddaughter’s sleep study! There is no good reason why a device that cost several thousand dollars should have such a poorly made power supply. The neighbor even asked me to turn in Russian broadcasts when there were rumors that something had happened. It seems the rumors were at least not totally bogus because the news segments were skipped. All they were transmitting was classical music.
Definitely easy fix for any ham radio as all ham radios works on same principles.Just on & off it and adjust frequency for station also antenna should be adjusted for best signal.
Equipment-generated noise is usually called QRN. This is opposed to QRM which is interference results from competing transmissions.