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Old 29th Apr 2022, 1:10 pm   #41
Lucien Nunes
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Default Re: Mains filtering

These are often delta caps: One X-cap L-N and two Y-caps L & N to E. Historically they were pass-through devices with inline chokes too, but those seem to have become less popular now. The frequency range of the offending emissions is probably narrower overall, being from SMPSUs rather than universal motors.
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Old 29th Apr 2022, 3:04 pm   #42
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Default Re: Mains filtering

Would it be possible/practical to fit X and Y caps to my distribution unit, either to the two main incomers or the RCDs? Has anyone done/tried that?
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Old 29th Apr 2022, 3:17 pm   #43
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Default Re: Mains filtering

Quote:
Originally Posted by stevehertz View Post
I've now added ferrite rings to my incoming mains supply (house), Still no better.
I'm not surprised Steve. To quote GM3SEK (referenced on the site you linked to in your first post):

"But also remember that an HF ferrite choke will typically need 6-8 turns passing through the centre hole. Regardless of the type of core, one pass through the centre will never be effective at HF!"

To see any significant difference I think you'll need to adopt the sort of filter that M0NWK and GM3SEK have described.

Hugh
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Old 29th Apr 2022, 3:41 pm   #44
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Default Re: Mains filtering

I think any form of mains filter would have to be 'tuneable' as such. Maybe more luck than science but recently when working on a Bush MB60 powered from the bench isolating transformer I connected a 4700pf 300v AC ceramic capacitor inside another 13 amp plug. When plugged into the double 13amp socket on the transformer output the noise was cut by about 70% but the frequency range of the interference suppressed is no doubt narrow.
LED replacement 'fluorescent' tubes generate an unbelievable racket over their entire length! Be warned if you intend to fit them over your bench and work on AM radios. Pity, the light is first class with very little shadow, not a problem for me because I work mainly with TV. John.
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Old 29th Apr 2022, 4:49 pm   #45
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Default Re: Mains filtering

Those with noise incoming on their mains - be suspicious of any nearby solar power installations, there have been reports of these causing such problems and exporting noise on the mains with cheap Chinese inverters being blamed .
See if there is any reduction in interference when the sun goes down.
Apart from this, large UPSs in nearby premises could be an issue also.
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Old 29th Apr 2022, 6:05 pm   #46
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Default Re: Mains filtering

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Originally Posted by Stockden View Post
Quote:
Originally Posted by stevehertz View Post
I've now added ferrite rings to my incoming mains supply (house), Still no better.
I'm not surprised Steve. To quote GM3SEK (referenced on the site you linked to in your first post):

"But also remember that an HF ferrite choke will typically need 6-8 turns passing through the centre hole. Regardless of the type of core, one pass through the centre will never be effective at HF!"

To see any significant difference I think you'll need to adopt the sort of filter that M0NWK and GM3SEK have described.

Hugh
Hugh, I agree, but snapping those clips on was a relatively easy process so I gave it a go. As this is the incoming mains supply to my house, not my 'shack', the installation - as can be seen in my photo - does not lend itself to taking multiple turns through a huge ferrite bead. In any case I'd probably be accused of tampering if I started to mess around with that wiring.

I've still not (quite) given up hope that there's something that can be done - even if I have to spend quite a bit of money for a professional installation - to reduce the interference on those incoming cables.
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Old 30th Apr 2022, 8:15 am   #47
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Default Re: Mains filtering

Hi Steve,

This one has really taxed my faded old brain but I had a few more thoughts overnight, so this will by my swansong:-

1. Firstly I wonder if your house had been wired in he old lead sheathed cable - similar to today's twin & earth would mitigate the problem.

With this in mind, rewiring with MICC aka PYRO 9copper sheathed) or FP200 (aluminium / pvc sheathed) may provide effective screening to the phase & neutral components. Obviously very disruptive & mega expensive though !

2. More realistically & on the presumption that you only listen to one station, could the radio chassis be relocated in an interference free area with the speaker & switch wires being extended to the room where you normally prefer to listen ? Along of course with the cabinet for aesthetic effect ?

Rog
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Old 30th Apr 2022, 9:26 am   #48
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Default Re: Mains filtering

Quote:
Originally Posted by colourking View Post
Those with noise incoming on their mains - be suspicious of any nearby solar power installations, there have been reports of these causing such problems and exporting noise on the mains with cheap Chinese inverters being blamed .
That is very interesting CK. There is a truly massive solar 'power station' around 4 miles away at Billingshurst West Sussex. I watched them bury the massive cables underground to run parallel with the main A29 adjacent to the site. May not be the problem but worth noting. John.
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Old 30th Apr 2022, 10:47 am   #49
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Default Re: Mains filtering

Regarding Y caps - these essentially inject RFI on L and N into the ground wire. That is why hospital grade mains filters do not have Y caps fitted - one X caps between L and N.

Craig
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Old 30th Apr 2022, 10:50 am   #50
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Default Re: Mains filtering

Quote:
Originally Posted by stevehertz View Post
... I've still not (quite) given up hope that there's something that can be done - even if I have to spend quite a bit of money for a professional installation - to reduce the interference on those incoming cables.
Single-phase filters rated up to 100A do exist, it seems https://uk.rs-online.com/web/p/power...ilters/5186272. The data sheet for that particular one suggests that you might hope for at least 40dB attenuation from 200kHz-20MHz, although obviously you'd want to confirm that with the manufacturer before investing a 3-figure sum.

I imagine a professional installation would be very wise, not least to make sure that there's adequate fault protection in place and that you don't risk upsetting your electricity supplier or invalidating your fire insurance. Personally I'd want anything like that put into its own screwed-shut steel box.

Cheers,

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Old 30th Apr 2022, 10:51 am   #51
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Default Re: Mains filtering

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Originally Posted by Craig Sawyers View Post
Regarding Y caps - these essentially inject RFI on L and N into the ground wire. That is why hospital grade mains filters do not have Y caps fitted - one X caps between L and N.

Craig
Why? Cheers.
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Old 30th Apr 2022, 10:56 am   #52
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Default Re: Mains filtering

Quote:
Originally Posted by Roger Ramjet View Post
Hi Steve,

This one has really taxed my faded old brain but I had a few more thoughts overnight, so this will by my swansong:-

1. Firstly I wonder if your house had been wired in he old lead sheathed cable - similar to today's twin & earth would mitigate the problem.

With this in mind, rewiring with MICC aka PYRO 9copper sheathed) or FP200 (aluminium / pvc sheathed) may provide effective screening to the phase & neutral components. Obviously very disruptive & mega expensive though !

2. More realistically & on the presumption that you only listen to one station, could the radio chassis be relocated in an interference free area with the speaker & switch wires being extended to the room where you normally prefer to listen ? Along of course with the cabinet for aesthetic effect ?

Rog
1) my house was rewired using up too date materials 30 years ago, for all intents and purposes, it's up to spec.

2) That's not something I'd do Roger! Obviously one can move things around and I can think of many things that I could do to 'improve' things, and I have done that in the past and now. My objective was, and is, to remove as far as it is possible, the RFI on my mains supply and house wiring. I accept it may not be feasible.
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Old 30th Apr 2022, 11:00 am   #53
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Default Re: Mains filtering

Because when a patient is attached to a machine, connection between the person connected to ground and live/neutral is generally not a good thing.

From Shaffner's data on medical grade mains filters "The B types of the Schaffner IEC inlet filters are designed without Y-caps due to the above mentioned
leakage-current requirements of MDs. All filter families are also available with an earth line choke"

Craig
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Old 30th Apr 2022, 11:02 am   #54
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Default Re: Mains filtering

Having said all that about filters, I have all the parts on hand for building the mains filter linked in the OP's post to feed my collection of Racal RA17 and accessories.

Craig
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Old 30th Apr 2022, 11:33 am   #55
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Default Re: Mains filtering

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Originally Posted by Craig Sawyers View Post
Having said all that about filters, I have all the parts on hand for building the mains filter linked in the OP's post to feed my collection of Racal RA17 and accessories.

Craig
Be interesting to know how you get on Craig.
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Old 1st May 2022, 8:34 am   #56
Craig Sawyers
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Default Re: Mains filtering

My RA17II is in late rebuild after five years plus in the attic (MHz and kHz tuning frozen). Then I recently acquired an ex GCHQ RA17W which needs a complete resistor and capacitor rebuild. Basically an RA17L with different IF bandwidths and a few other minor mods.

An RA37 LF convertor which is fully working
An RA98 ISB unit, recently restored, but with an oil leak from the mains transformer. Replacement transformer on hand to replace it.
An RA63 sideband adaptor
A NOS RA121 - a sideband adaptor with a CRT screen to indicate tuning. Having said that, many resistors read high - 50% or so - which must have happened in storage. So weirdly for a NOS unit it needs laying on of hands.

Once I have at least one receiver up and running, I'll get the mains filter built and do some tests - which I'll report here.

Craig
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Old 1st May 2022, 1:28 pm   #57
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Default Re: Mains filtering

Just a thought - but it looks like (from your pictures) you have an old-style
'smart' meter which I think transmits on the old 2/3G network.

Could this be a source of your problems?
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Old 1st May 2022, 3:03 pm   #58
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Just a thought - but it looks like (from your pictures) you have an old-style
'smart' meter which I think transmits on the old 2/3G network.

Could this be a source of your problems?
Can someone answer this?
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Old 2nd May 2022, 10:37 am   #59
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Default Re: Mains filtering

If the meter is suspect then there is some hope perhaps for your situation..

If it is on 3G then they will probably replace it with a new type of simpler unit operating on 4/5G soon, as they are closing the 3G network sometime in the next year or so.
.. but are keeping 2G for simple, emergency situations.. but obviously don't know if that applies to your meter as 2G may not be enough to give them the data they require from your installation.

The newer types of smart meter instals now have the transmitter separate from the meter.
If you cannot find a solution elsewhere and it continues to drive you up the wall it might be something you want to
talk to your meter supplier about as the early smart meters were only concerned with getting data out of you, and they may have had similar complaints to yours causing them to re-design the later meters.

Last edited by cheerfulcharlie; 2nd May 2022 at 10:57 am.
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Old 2nd May 2022, 10:54 am   #60
stevehertz
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Default Re: Mains filtering

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If the meter is suspect then there is some hope perhaps for your situation..

If it is on 3G then they will probably replace it with a new type of simpler unit operating on 4/5G soon, as they are closing the 3G network sometime in the next year or so.
.. but are keeping 2G for simple, emergency situations.. but obviously don't know if that applies to your meter as 2G may not be enough to give them the data they require from your installation.
I've no reason to believe that there's anything wrong with the meter, it's worked perfectly as 'a meter' since it's been installed. Someone else raised the question of 'its type' perhaps being a problem re interference.
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