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Old 16th Nov 2022, 3:23 pm   #21
winston_1
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Default Re: Valve amplifier picking up EMI/RFI

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Originally Posted by Roger Ramjet View Post
I would suspect the Power Line adapters because they piggy back signals direct onto the house wiring.

Rog
Which is not designed to carry data so it radiates and causes interference for several hundred metres.

Just get rid of them for your neighbours sake even if they are not the cause of your problem.

https://www.ispreview.co.uk/index.ph...-adapters.html
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Old 16th Nov 2022, 4:41 pm   #22
Gabe001
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Default Re: Valve amplifier picking up EMI/RFI

My neighbour has more powerline extenders than I do!
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Old 16th Nov 2022, 7:10 pm   #23
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Default Re: Valve amplifier picking up EMI/RFI

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My neighbour has more powerline extenders than I do!
That can be fixed...

Just mention near them that powerline adaptors radiate all their data traffic and that with suitable gear and intent, it can be monitored from several hundred metres...

David
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Old 16th Nov 2022, 11:35 pm   #24
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Default Re: Valve amplifier picking up EMI/RFI

I've just installed two super new RFI generators
The induction hob is just wonderful for cooking, can't be left on inadvertently, doesn't even get hot, but when it's on it generates enough 20kHz and harmonics to wipe out LW, MW, and up to 49 meters. A battery charger / pulse reconditioner is just wonderful for charging old batteries and also wipes out the FM band, but at least you can choose when to use it!
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Old 17th Nov 2022, 8:25 am   #25
Gabe001
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Default Re: Valve amplifier picking up EMI/RFI

Update. It turns out it is mains borne interference. The culprit is something in the garden, as turning off this circuit stops the clicking/popping completely. Probably either the pond pump (350W), the filter UV lamp or the pond aerator, but could be one of the connections or the garden circuit breaker. Won't be too hard to pinpoint the culprit now. These will be off during the winter anyway but I'll investigate further shortly.

Thanks for the help.
Gabriel

Ps: I'd get rid of the fish, but the boss says no

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Old 17th Nov 2022, 1:03 pm   #26
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Default Re: Valve amplifier picking up EMI/RFI

Starter switch for the UV tube? Tubes and starters have finite lives.

Otherwise you may be looking into the fish's internet connection.

David
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Old 19th Nov 2022, 8:08 am   #27
Gabe001
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Default Re: Valve amplifier picking up EMI/RFI

And a picture of the culprit. It's the 24W UV lamp for the pond filter

Do you think it's worth writing this up in the bvws journal as an unusual cause of amplifier noise?
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Old 19th Nov 2022, 9:22 am   #28
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Default Re: Valve amplifier picking up EMI/RFI

It's a source of interference not many will think about. People with private water supplies have similar things to kill bacteria in their spring water. EMC problems with valve amps are rare, so it's a tale of successful sleuthing in unusual circumstances.

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Old 19th Nov 2022, 10:04 am   #29
Jan Zodiac
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Default Re: Valve amplifier picking up EMI/RFI

Some time ago I had a lot of noise when listening to FM. I had a hard time figuring out what it could be, since it only appeared sometimes, and always in the evening. The noise made it impossible to use the FM band, especially on the lower frequencies. I was sure it was a charger or the internet router, but disconnecting them made no difference.

It turned out to be a light bulb. Not an LED type, but the one shown in the picture. They are probably cheap production ones, as the supports for the filament tends to loosen after some time of use, and when watching the filament carefully, it actually vibrates a little, probably from the mains frequency.
Where the filament strings are very close to each other, I believe they make contact and creating some kind of spark which is not visible to the eye, but certainly audible when listening to FM. Never had I ever suspected a light bulb to be such an effective noise transmitter. Nowhere in the house was it possible to use the FM band when light was on in the kitchen.

Jan
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Old 19th Nov 2022, 10:25 am   #30
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Default Re: Valve amplifier picking up EMI/RFI

Fish pond UV tubes with SMPS supplies create many spurs on the 70MHz band all spaced 35kHz apart.

On the incandescent bulbs there is some VHF oscillation mechanism that happens with them.

https://www.ofcom.org.uk/about-ofcom...rference-issue
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Old 19th Nov 2022, 10:44 am   #31
Gabe001
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Default Re: Valve amplifier picking up EMI/RFI

You know what, reading the article I think that's the same light bulb Jan pictured in her kitchen in the post above yours.

We actually have one similar to that in the house, in a Tiffany type lamp. Luckily it's hardly ever on.
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Old 19th Nov 2022, 12:58 pm   #32
Jan Zodiac
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Default Re: Valve amplifier picking up EMI/RFI

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Originally Posted by Gabe001 View Post
You know what, reading the article I think that's the same light bulb Jan pictured in her kitchen in the post above yours.

We actually have one similar to that in the house, in a Tiffany type lamp. Luckily it's hardly ever on.
That is indeed the same type of bulb. I had no clue they could emit that amount of RFI
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Old 22nd Nov 2022, 9:09 pm   #33
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Default Re: Valve amplifier picking up EMI/RFI

Interesting stuff. I have a couple of Radford valve amps that pick up RFI quite badly from an ethernet power line box. Where as the Leak ST20 is completely silent.

I was going to try swapping a couple of valves around in the Radford, but as the interference is a similar level on both channels it would suggest that it is mains bourne.

I bought a couple of ferrite clamps for the Radfords mains leads, away on holiday atm so no chance to try yet.

...we have a UV in the pond pump...
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