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Terrible high frequency noise from guitar is killing my recordings DJ Controllers
Old 12th January 2018
  #31
Quote:
Originally Posted by Tobias Valentin View Post
Sorry to bring up this topic again. I am about to go mental.

New info:
Until now, I have only heard the high pitched noise during guitar recordings (and playback) in my home studio. Same noise, same pitch, in every amp, anywhere in the house.

But today, I realised that the exact same pitch is also constantly in my studio speakers.
Tried to switch off all electronics in the house again, except for the speakers. The noise was still there, and it's the same noise as heard in guitar amps: it's equivalent to H7 on the piano (almost 4 octaves above middle C). And vice versa: The guitar amps also produce the noise if the studio speakers (and everything else) is switched off. So, it must be the same cause across all speakers here.

- The noise is definitely not on recordings made through the audio interface, although the speakers are connected to the interface.
- The noise will be on such recordings, if a guitar is recorded through the Hi-Z function of the audio interface, but the reason must be that the pickups of the guitar receives the noise, not the audio interface itself.
- Also, as mentioned, any guitar amplifier here will produce the high pitch noise, when switched on - with or without a guitar plugged.

Does this problem sound familiar to anyone?
WHAT IS CAUSING THIS?!
Do you have any of the new LED light bulb replacements? LED lights incorporate a tiny switching power supply. Such power supplies can generate bad RFI if they don't incorporate adequate noise suppression filters. Some of the worst offenders are from well respected household names, like (but by no means limited to) Phillips.

If you have such lights, disconnect/unscrew them and see if the noise persists.
Old 12th January 2018
  #32
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Quote:
Originally Posted by Tobias Valentin View Post
Sorry to bring up this topic again. I am about to go mental.

New info:
Until now, I have only heard the high pitched noise during guitar recordings (and playback) in my home studio. Same noise, same pitch, in every amp, anywhere in the house.

But today, I realised that the exact same pitch is also constantly in my studio speakers.
Tried to switch off all electronics in the house again, except for the speakers. The noise was still there, and it's the same noise as heard in guitar amps: it's equivalent to H7 on the piano (almost 4 octaves above middle C). And vice versa: The guitar amps also produce the noise if the studio speakers (and everything else) is switched off. So, it must be the same cause across all speakers here.

- The noise is definitely not on recordings made through the audio interface, although the speakers are connected to the interface.
- The noise will be on such recordings, if a guitar is recorded through the Hi-Z function of the audio interface, but the reason must be that the pickups of the guitar receives the noise, not the audio interface itself.
- Also, as mentioned, any guitar amplifier here will produce the high pitch noise, when switched on - with or without a guitar plugged.

Does this problem sound familiar to anyone?
WHAT IS CAUSING THIS?!
If it’s not in your battery powered amp but it’s in everything else wall connected such as your studio monitors, it’s your power. Something bad with your wiring, or one of your neighbors has some janky stuff plugged in.

I would contact the landlord, see if they could get an electrician out on their dime. But in my experience, you’ll probably have to get one out yourself.
Old 12th January 2018
  #33
Quote:
Originally Posted by kslight View Post
If it’s not in your battery powered amp but it’s in everything else wall connected such as your studio monitors, it’s your power. Something bad with your wiring, or one of your neighbors has some janky stuff plugged in.

I would contact the landlord, see if they could get an electrician out on their dime. But in my experience, you’ll probably have to get one out yourself.
A high frequency noise is probably NOT transmitted over the power line. Most power related noise problems are low frequency, between 50Hz and 120Hz depending on location. High frequency noises are nearly always caused by RFI (Radio Frequency Interference) or EMI (ElectroMagnetic Interference) and are transmitted through the air. Common sources are lighting dimmers, switching power supplies found in everything from computers to LED room lighting to inexpensive audio equipment, neon or fluorescent lighting, nearby radio transmitters, emissions from poorly shielded computers and cheap video,. USB, and similar cables (including defective connectors) and a host of other sources.

Poorly filtered switching power supplies constitute a rapidly growing problem. Many, if not most modern wall warts are now switching supp[lies, asd they are much cheaper to produce than traditional (transformer based) linear supplies and are usually "universal voltage" that can operate on any voltage from 85VAC to 240VAC. The problem is that they operate internally in the lower radio frequency band and if they do not contain adequate HF filtering they spew noise like little radio stations. Such filtering does not affect their operation as a power supply for non-RF sensitive equipment and adds significantly to the cost of the supply, so some companies omit it. Every LED light bulb that runs off house current contains a tiny switching supply. Recently there have been several articles published on the noise problem caused by inadequate filtering in these devices, with examples of low noise and high noise brands; unfortunately none of these lists are comprehensive. The problem is exacerbated by recent government regulations promoting the use of LED lighting and discouraging/penalizing the use of traditional incandescent bulbs for reasons of reduced power consumption.
Old 12th January 2018
  #34
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Muser's Avatar
jump to 20 mins to see what he finds out.

Old 12th January 2018
  #35
I watched that whole vid like it was a new episode of The X Files. Cool guy, finding the cause of the noise
Old 12th January 2018
  #36
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yeah it was a good investigation. I use a telephone bug plugged into a portable speaker often. but it would be nice to be armed with a few simple tactics and methods to check. maybe a radio is often too sensitive. I don't really use that method so I'm unsure. but finding some simple way to gauge noise in the mains itself could be handy.
Old 12th January 2018
  #37
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They can be a little pricey but Ebtech Hum X units really work great. Even if folks think it might not be a grounding issue, i'd still try one or three if you cant track down a source of interference and its still bugging you. These can at least help rule out ground loop issues.

Ebtech also makes units that run audio channels (not power) through 1:1 transformers to isolate the signals, they make single channel and 8 channel rack versions. I'd try to avoid that, but the 1-channel version might be helpful to troubleshoot.

Could be something from a neighbors place putting out interference, thats tough. If you can find the source, copper shielding is relatively inexpensive to doink around with, try to limit it. My uncle is a ham radio operator and has copper shielding and ferrite cores on eeeeeverything. Havent ever had too big a problem i couldnt resolve though, usually its lighting (neon in the old days, led now) or computers, wifi, bluetooth, printers, dimmer switches, "touch" lamps, those little gimmick electricity ball toys, etc. haha
Old 13th January 2018
  #38
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Thread Starter
Quote:
Originally Posted by Muser View Post
could be LED lights etc or maybe someone something next door or something injecting noise into the mains which has started badly performing.

What does it mean, "the mains"? (You will have me excused, I know very little about electric systems).

And what, for example, could be injecting noise into them?
Old 13th January 2018
  #39
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Thread Starter
Quote:
Originally Posted by bowzin View Post
They can be a little pricey but Ebtech Hum X units really work great. Even if folks think it might not be a grounding issue, i'd still try one or three if you cant track down a source of interference and its still bugging you. These can at least help rule out ground loop issues.

Ebtech also makes units that run audio channels (not power) through 1:1 transformers to isolate the signals, they make single channel and 8 channel rack versions. I'd try to avoid that, but the 1-channel version might be helpful to troubleshoot.

Could be something from a neighbors place putting out interference, thats tough. If you can find the source, copper shielding is relatively inexpensive to doink around with, try to limit it. My uncle is a ham radio operator and has copper shielding and ferrite cores on eeeeeverything. Havent ever had too big a problem i couldnt resolve though, usually its lighting (neon in the old days, led now) or computers, wifi, bluetooth, printers, dimmer switches, "touch" lamps, those little gimmick electricity ball toys, etc. haha
Thanks for the tips. Could be the way to troubleshoot.
Old 13th January 2018
  #40
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Thread Starter
Quote:
Originally Posted by Henrik Hjortnaes View Post
I watched that whole vid like it was a new episode of The X Files. Cool guy, finding the cause of the noise


He is a fighter.
Old 13th January 2018
  #41
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Thread Starter
Quote:
Originally Posted by John Eppstein View Post
Most power related noise problems are low frequency, between 50Hz and 120Hz depending on location. High frequency noises are nearly always caused by RFI (Radio Frequency Interference) or EMI (ElectroMagnetic Interference) and are transmitted through the air. Common sources are lighting dimmers, switching power supplies found in everything from computers to LED room lighting to inexpensive audio equipment, neon or fluorescent lighting, nearby radio transmitters, emissions from poorly shielded computers and cheap video,. USB, and similar cables (including defective connectors) and a host of other sources.
I tried to unplug everything here, except the speakers, and the sound was still there, but it would come from some of the neighbours, or, as you mention, radio transmitters.

Still, I think it could be the power.
Old 13th January 2018
  #42
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Thread Starter
Quote:
Originally Posted by kslight View Post
If it’s not in your battery powered amp but it’s in everything else wall connected such as your studio monitors, it’s your power. Something bad with your wiring, or one of your neighbors has some janky stuff plugged in.

I would contact the landlord, see if they could get an electrician out on their dime. But in my experience, you’ll probably have to get one out yourself.
Yes, it seems that it could be the power. I will contact our electrician, and hope the task is not too hard to solve here; it's a 5 floors, early 20th century building in Copenhagen. Lately, there has been some issues with some of the old "gear" in the building, though the lift from that period is still running safely.
Old 13th January 2018
  #43
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Muser's Avatar
Quote:
Originally Posted by Tobias Valentin View Post
What does it mean, "the mains"? (You will have me excused, I know very little about electric systems).

And what, for example, could be injecting noise into them?
in his case, the signal actually appearing on the power lines. because the power pole is arcing and burning away the wood as it does so. that's why I say, if it's possible to find a really simple way to see if there are bad signals on the power line. that would be great. because if you can always simply check and find there no such signals. you're ok in that respect. if you find some, the rest is then about figuring out what is causing the problem. because no one else will ever really figure it out for you. you have to have strategies. preferably using simple ready made equipment. rather than specialist kit.

Last edited by Muser; 13th January 2018 at 06:47 PM..
Old 13th January 2018
  #44
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Muser's Avatar
guy uses radio.

Old 13th January 2018
  #45
Quote:
Originally Posted by Muser View Post
in his case, the signal actually appearing on the power lines. because the power pole is arcing and burning away the wood as it does so. that's why I say, if it's possible to find a really simple way to see if there are bad signals on the power line. that would be great. because if you can always simply check and find there no such signals. you're ok in that respect. if you find some, the rest is then about figuring out what is causing the problem. because no one else will ever really figure it out for you. you have to have strategies. preferably using simple ready made equipment. rather than specialist kit.

Quote:
Originally Posted by Muser View Post
jump to 20 mins to see what he finds out.

Great video, BUT -

That's not noise on the power line, that's RF through the air. The RF is being generated by an arc (a big, persistent spark) caused by a defective power pole device, but the noise is a radio transmission through the air, not on the power line itself. This is the same type of Radio Frequency Interference that is frequently caused by arc welding rigs.

Fact is, the problem discovered in the video would cause problems even in equipment that had no connection at all to the defective power line equipment causing the problem. It could be in a completely separate section of the power grid as long as it's physically within "line of sight", i.e. not over the horizon.

Actually, if you had been paying attention, he eliminated any possibility of noise transmitted over the power line itself in the first minute and a half of the video.

Last edited by John Eppstein; 13th January 2018 at 09:05 PM..
Old 13th January 2018
  #46
Quote:
Originally Posted by Muser View Post
yeah it was a good investigation. I use a telephone bug plugged into a portable speaker often. but it would be nice to be armed with a few simple tactics and methods to check. maybe a radio is often too sensitive. I don't really use that method so I'm unsure. but finding some simple way to gauge noise in the mains itself could be handy.
The noise is not in the mains. Any noise of that frequency in the mains would be filtered out and eliminated by the power supply of any audio electronics you were using.

The problem is airborne radio transmission.
Old 13th January 2018
  #47
Quote:
Originally Posted by bowzin View Post
They can be a little pricey but Ebtech Hum X units really work great. Even if folks think it might not be a grounding issue, i'd still try one or three if you cant track down a source of interference and its still bugging you. These can at least help rule out ground loop issues.

Ebtech also makes units that run audio channels (not power) through 1:1 transformers to isolate the signals, they make single channel and 8 channel rack versions. I'd try to avoid that, but the 1-channel version might be helpful to troubleshoot.

Could be something from a neighbors place putting out interference, thats tough. If you can find the source, copper shielding is relatively inexpensive to doink around with, try to limit it. My uncle is a ham radio operator and has copper shielding and ferrite cores on eeeeeverything. Havent ever had too big a problem i couldnt resolve though, usually its lighting (neon in the old days, led now) or computers, wifi, bluetooth, printers, dimmer switches, "touch" lamps, those little gimmick electricity ball toys, etc. haha
Ground loops are low frequency hums or buzzes. If it's a buzz it sounds higher in pitch than the fundamental because of higher harmonics in a distorted sine wave, but the fundamental will still be line frequency or double line frequency.

The Ebtech devices are great for breaking ground loops but are not effective on environmental RFI or EMI.

EMI, although somewhat rarer, can be particularly nasty because RF shielding is not effective against it sincer it's magnetic in nature, not radio.
Old 13th January 2018
  #48
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Muser's Avatar
Quote:
Originally Posted by John Eppstein View Post
The noise is not in the mains. Any noise of that frequency in the mains would be filtered out and eliminated by the power supply of any audio electronics you were using.

The problem is airborne radio transmission.
but it could still come via the mains and then radiate into the environment before filtering. then be picked up.
hopefully it's not in the mains. unless that turns out to be a simpler solution if it is.
Old 13th January 2018
  #49
I've had sporadic problems with a similar noise in my studio (through he tube guitar amp, and in the studio monitors). My landlord is an ex-satellite dish installer/electrician and tells me it's probably because we live so close to the Eiffel Tower, where there are many many RF and cell phone transmitters and devices stationed. We think it's the same signal that sometimes messes with our aircon switching on and off. I haven't asked him if that's RFI or EMI, and haven't taken any steps yet to get rid of it. It only bothers me when it's actually there (maybe about a fifth of the time) in the guitar amp AND I want to record, which isn't so often. When it's in the studio monitors it's a mild distraction, but as it's so low and doesn't get on to any recordings, it's not so bad. I need to measure the actual frequency, but it sounds about where yours is. We have dimmers and LED light bulbs here, but I've tested things by turning them on and off and it doesn't make a difference. So I blame the Eiffel Tower...
Old 14th January 2018
  #50
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Muser's Avatar
I'd say this is quite a good general round up. I have seen in the past, people using old uninterruptible PSU units for various things. some of them have software which can monitor power. so I guess, some old ones where the batteries have worn out, might still have a functioning scope software.

analysing the cleanliness of the power is often done on some kind of scope. I have never seen some simple cheap kind of scope capable of that. but there might be something. it seems to me possible that you could help detect some mall functioning equipment fault that way. it might not prove to be the source, but it could always be handy to know what's showing up on the power line.

these are just general rounding up of possibilities. the simplest solutions are often the best imo.

Old 14th January 2018
  #51
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I just had a quick scout around with my best Radio. it's a very expensive sony I've had for years set on the low side of the AM band. I have mainly LED lights but they are low power. I have USB powered lights, a normal LED bulb and a roll of coloured LEDs. can't say I picked any real problems up. then again, I tend to follow youtube channels of people who find trash products. so I tend to choose things I know are ok.

I've also checked my system with telephone bugs often enough. the worst offenders were not my LED's. they were often transformer based PSU's. on those I pick hum within 3 to 4 feet and it gets worse the closer you get. the switching units are far less noisy and emit at a far lesser significant distance. they can have traces though, in audio signals. especially if DSP based audio gear.

but that's not to say you don't have a really bad LED bulb. it might just mean that I don't. if someone on a property is pulling a lot of power through an LED lighting unit, and it's also trash. that could produce a high amount I guess. I don't have experience of it.

anyhow. here's some unit I came across just now. I don't have it so can't vouch.

Old 15th January 2018
  #52
Quote:
Originally Posted by Muser View Post
I'd say this is quite a good general round up. I have seen in the past, people using old uninterruptible PSU units for various things. some of them have software which can monitor power. so I guess, some old ones where the batteries have worn out, might still have a functioning scope software.

analysing the cleanliness of the power is often done on some kind of scope. I have never seen some simple cheap kind of scope capable of that. but there might be something. it seems to me possible that you could help detect some mall functioning equipment fault that way. it might not prove to be the source, but it could always be handy to know what's showing up on the power line.

these are just general rounding up of possibilities. the simplest solutions are often the best imo.

Any functioning analog scope is capable of detecting dirty power, even an uncalibrated 10MHz Heapsh!t from a garage sale. It's simple - is the sine wave a sine wave?

Not all UPSes are created equal. Some output a square wave, some are "quasi sine wave" which is actuality a stepped square wave, and a very few output a real sine wave. Additionally, some output the line power when they are in "normal" mode and only switch to battery backup (and their own waveform generation) when in backup mode.

In other words, all but the most costly UPSes are useless for power line filtration. And if the batteries are worn out they're also useless.

I have yet to encounter ANY UPS software that can effectively monitor for dirty power. There ARE power line filtration/ reconstitution devices that can do this, but they are not standard UPSes, although there are devices that are multi-function. Most power line monitoring software can only detect brownouts, overvoltage, and spikes, it can't detect waveform distortion and noise.

I have not watched the video yet, I'll do so later and comment if necessary.
Old 15th January 2018
  #53
Quote:
Originally Posted by Muser View Post
I just had a quick scout around with my best Radio. it's a very expensive sony I've had for years set on the low side of the AM band. I have mainly LED lights but they are low power. I have USB powered lights, a normal LED bulb and a roll of coloured LEDs.
USB powered light generally are not a problem because USB power is already low voltage DC, no switching supply is required.

Quote:
can't say I picked any real problems up. then again, I tend to follow youtube channels of people who find trash products. so I tend to choose things I know are ok.
I trust the majority of YooToob vids about like I trust politicians with orange dyed combovers.

Quote:

I've also checked my system with telephone bugs often enough. the worst offenders were not my LED's. they were often transformer based PSU's. on those I pick hum within 3 to 4 feet and it gets worse the closer you get. the switching units are far less noisy and emit at a far lesser significant distance. they can have traces though, in audio signals. especially if DSP based audio gear.
Er, no - you're confusing RFI with EMI.

Transformers put out quite strong magnetic fields (EMI) because transformers are electromagnetic devices. However, in most cases EMI is relatively short range - magnetism doesn't carry very far.

Switching supplies, OTOH, put out very, very little EMI because the only transformers in them are TINY because high frequency transformers don't need to be very big or contain larger magnetic components. Therefore the techniques you're outlining, which work for EMI, are more or less useless for detecting noise from switching supplies which operate on radio frequency energy - in essence a switching supply is a small radio transmitter spewing radio frequency noise (RFI) into the environment - and RFI has a much longer range than EMI. This radio frequency energy can be picked up by anything capable of functioning as an antenna - like a guitar pickup or an unterminated cable, and can then be demodulated by anything capable of acting as an RF detector diode (think the crystal in an old crystal radio set), which can be a semiconductor junction in any solid state device, a slightly imperfect solder joint (the original crystal sets used a crystal of lead sulfide (aka Galena) as the detector diode, which is functionally very similar to a cold solder joint), or even a tiny bit of dirt or corrosion in a switch, jack, or tube socket contact - turning the RF noise into audio noise.

It's too bad they don't teach kids about this stuff anymore, but the powers that be decided that Galena crystals constitute a danger of lead poisoning to children, so the once ubiquitous crystal radio sets I grew uo with are no longer available, replaced by sets employing a glass encased diode which obscures the principle involved in how the thing works.

Quote:
but that's not to say you don't have a really bad LED bulb. it might just mean that I don't. if someone on a property is pulling a lot of power through an LED lighting unit, and it's also trash. that could produce a high amount I guess. I don't have experience of it.
Er, no. You don't "pull power through" an LED bulb. The LEDs draw what they draw, period - but that's not the problem. The problem is that LEDs require low voltage DC power to operate efficiently, so the relatively high voltage AC power must be converted to low voltage DC. This requires a power supply, and to be practical a small switching supply is used. A linear supply would need a relatively bulky transformer containing expensive copper wire (expensive when you're making huge quantities of bulbs, anyway), and that just wouldn't be cost effective or physically practical. So every LED bulb contains a tiny switching power supply which, as we have seen, is functionally a tiny but efficient RF generator. Now this obnoxious RFI leakage can be easily suppressed by adding a couple of filter capacitors to the circuit - but this ADDS TO THE COST and dopesn't do anything for the functionality of the LED bulb as a light, so some companies simply omit them or employ inadequate filtration. Hey, a few pennies per bulb difference really adds up when you make thousands or millions of bulbs per day!

And your techniques for detecting EMI emissions that work on transformers are utterly useless in detecting RFI.

Quote:

anyhow. here's some unit I came across just now. I don't have it so can't vouch.

I haven't checked out that particular unit yet, but so far nearly all the similar detectors I've seen are for EMI, not RFI.

Again, EMI and FRI are NOT the same.

EDIT: OH, WAIT! I don't have to check it out after all - it says right on the front panel of the unit in the picture "EMI METER"!

Useless for detecting RFI from LED bulbs, switching supplies, etc.

Last edited by John Eppstein; 15th January 2018 at 08:44 PM..
Old 15th January 2018
  #54
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Last edited by AuldLangSine; 15th January 2018 at 06:47 AM..
Old 15th January 2018
  #55
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Muser's Avatar
Quote:
Originally Posted by John Eppstein View Post
USB powered light generally are not a problem because USB power is already low voltage DC, no switching supply is required.
yes I know. that's why I use them.

Quote:
I trust then majority of YooToob vids about like I trust politicians with orange dyed combovers.
so do I.


Quote:
Er, no - you're confusing RFI with EMI.
Transformers put out quite strong magnetic fields (EMI) because transformers are electromagnetic devices. However, in most cases EMI is relatively short range - magnetism doesn't carry very far.

Switching supplies, OTOH, put out very, very little EMI because the only transformers in them are TINY because high frequency transformers don't need to be very big or contain larger magnetic components. Therefore the techniques you're outlining, which work for EMI, are more or less useless for detecting noise from switching supplies which operate on radio frequency energy - in essence a switching supply is a small radio transmitter spewing radio frequency noise (RFI) into the environment - and RFI has a much longer range than EMI. This radio frequency energy can be picked up by anything capable of functioning as an antenna - like a guitar pickup or an unterminated cable, and can then be demodulated by anything capable of acting as an RF detector diode (think the crystal in an old crystal radio set), which can be a semiconductor junction in any solid state device, a slightly imperfect solder joint (the original crystal sets used a crystal of lead sulfide (aka Galena) as the detector diode, which is functionally very similar to a cold solder joint), or even a tiny bit of dirt or corrosion in a switch, jack, or tube socket contact - turning the RF noise into audio noise.
the technique with the bug detects a fair amount. It detected a broken switching PSU for a USB hub and narrowed it down in about one minute. and I can also easily hear the hum on the transformer based gear easily enough. which is all I generally really need to do. it also picks activity in all kinds of other gear. moving over a computer etc. it's often short range, but some of the transformer wallwart PSU's hum within 3 to 4 feet.

Quote:
It's too bad they don't teach kids about this stuff anymore, but the powers that be decided that Galena crystals constitute a danger of lead poisoning to children, so the once ubiquitous crystal radio sets I grew up with are no longer available, replaced by sets employing a glass encased diode which obscures the principle involved in how the thing works.
I don't think I have a crystal radio. I don't know if I ever have.

Quote:
Er, no. You don't "pull power through" an LED bulb. The LEDs draw what they draw, period - but that's not the problem. The problem is that LEDs require low voltage DC power to operate efficiently, so the relatively high voltage AC power must be converted to low voltage DC. This requires a power supply, and to be practical a small switching supply is used. A linear supply would need a relatively bulky transformer containing expensive copper wire (expensive when you're making huge quantities of bulbs, anyway), and that just wouldn't be cost effective or physically practical. So every LED bulb contains a tiny switching power supply which, as we have seen, is functionally a tiny but efficient RF generator. Now this obnoxious RFI leakage can be easily suppressed by adding a couple of filter capacitors to the circuit - but this ADDS TO THE COST and dopesn't do anything for the functionality of the LED bulb as a light, so some companies simply omit them or employ inadequate filtration. Hey, a few pennies per bulb difference really adds up when you make thousands or millions of bulbs per day!
there are some higher power LED systems out there, in overall power terms. relatively speaking. so even though the forward voltages can be low for the individual LED's, there's a question to how they arrange so many of them and the issue of the design of the power supply quality. it's often the mosfets which break down quickly especially in colour changing LED's. not that I detect much noise when they do. I try to stick with lower power solutions in any case.

Quote:
And your techniques for detecting EMI emissions that work on transformers are utterly useless in detecting RFI.
maybe that's where the radio is more effective.

Quote:
I haven't checked out that particular unit yet, but so far nearly all the similar detectors I've seen are for EMI, not RFI.

Again, EMI and FRI are NOT the same.

EDIT: OH, WAIT! I don't have to check it out after all - it says right on the front panel of the unit in the picture "EMI METER"!

Useless for detecting RFI from LED bulbs, switching supplies, etc.
it may well be. let me know if you come across anything. so far my system seems pretty clean overall. a couple of things could do with cleaning up a bit more.
Old 15th January 2018
  #56
Quote:
Originally Posted by AuldLangSine View Post
Radiation protection built into your new home design › GEOVITAL Academy - Academy for Radiation Protection and Environmental Medicine - Radiation shielding fitted to entire apartment complex - The world in changing and consumer needs are changing. Progressive deve... JB
That's a bit of a hype - steel frame concrete buildings are inherently shielded against RFI, which is why cell phones and radios generally don't work in them (which I imagine that builder does not bother to mention...)
Old 15th January 2018
  #57
Quote:
Originally Posted by AuldLangSine View Post
JB
That's a bit of a hype - steel frame concrete buildings are inherently shielded against RFI, which is why cell phones and radios generally don't work in them (which I imagine that builder does not bother to mention...)

MUSER - The radio is a good but somewhat imperfect solution for RFI detection, the problem being that domestic radios are selective for commercially used bandwidths, whereas RFI is not and often radiates in frequency bands outside the tuning range of the radio. Still, it's much better than nothing.
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