IEC connector in-line suppressor

[usenet]

I'm looking for an 'in line' IEC male/female suppressor thingy that I can plug in series with the mains supply going into a PC. (I could probably do with more than one actually).

I've been recommended this as a solution to the amount of EMI/RFI radiated by one of my PC's power supplies (typically it's the one that's normally on all the time). The amount of noise it radiates is interfering with radio reception, it's particularly bad in the 1MHz to

2MHz range with a peak at around 1400kHz. It doesn't just interfere with radios in the same room, it affects reception badly elsewhere in the house.

I'm just getting back into SWLing and such so suggesting that I use VHF/FM instead is *not* a solution! :-)

I've tried Google searches but without much success as one gets zillions of hits with "IEC filter" and they're just about all chassis mounting plugs and similar. It's also quite difficult to find filters that are specifically designed to prevent radiation *from* the PC rather than being devices to protect the PC.

Any help finding filters for this type of application would be very welcome. If in-line IEC ones aren't forthcoming I wouldn't be too unhappy wiring something up but it needs to be close to (or even within) the PC power supply to be able to prevent it radiating.

[Robin Prater]

There is a range of filters made by Belling Lee and Schaffner probably for medical use - sold by CPC. With a bit of care you may be able to mount one in the power supply, or fit it in a die cast box outside.

Others may have better ideas.

[usenet]

Thanks, that's the first retails supplier of this that I've seen.

Yes, that's the problem, it's a device for stopping nasties getting in to the PC rather than one for stopping noise getting out.

[Christian McArdle]

You might have a poorly designed power supply. It is relatively easy (and not horrendously expensive) to find replacements for standard ATX supplies which may operate better.

Christian.

[Dave Plowman]

This is a job the makers should have done. It can be pretty time consuming trying to cure RFI. Might be easier to get a power supply that does conform - although they'll all produce some interference at MF if the radio is close.

[N. Thornton]

Hi

A surge suppressor wont make any difference to that. As for Lc filtering your PSU already has lots of that in it already. You need to talk to sci.electronics.design for an expert approach.

Regards, NT

[fred]

In article , [e-mail] writes

Sorry, haven't seen any ready made IEC lead filters. The surge suppressor mentioned elsewhere in the thread will not do the job (it is not a filter). If you are prepared to do a little DIY, then the following may help.

Good news, that's pretty low in terms of RFI so returns from filtering should be relatively easy to find. The range suggests crap from the switch mode power supply being passed conducted to your receiver or re-radiated by the mains wiring of your house to your aerial. As a quick check on the source, disconnect your mouse & keyboard and see if the interference is reduced, hopefully it won't be. Then, switch off the monitor to see if it is coming from there. Anything left is coming from the computer itself.

As a first hit you could make up a pigtail from and IEC equipment filter and a the socket from the end of an IEC mains lead. A cheap and cheerful source for the filter would be Maplin code UT90X. Cut down the IEC lead to

150mm & solder to the filter. Make safe with a large heatshrink boot & plug directly into the back of the PC.

If this improves your situation, then we are on the right track. If it improves, but does not eliminate, then move to a better quality filter eg Maplin code MG54J, if it does nothing, then we need to think again.

Don't worry about getting the filter inside the case as at 1400kHz your mains wiring is a very inefficient radiator to start with:

1400kH 1/4 wavelength = 214m 3m cable radiation efficiency -37dB 1m cable radiation efficiency -47dB 150mm cable radiation efficiency -63dB , so I reckon you are only seeing this problem because of a v sensitive receiver.

Whilst your PC supply may be substandard, that is only a possibility & a

10quid filter may save you the expense of a 50quid supply that may not fix the problem.

I have assumed that the PC isn't sitting right beside the receiver . . . . tell me that is the case ;-)

Btw: Once you have one of these made up, try plugging the receiver ito it as well, to check that the interference is not coming in conducted from the mains.

HTH

[fred]

In article , fred writes

Ok, so it was a long day, correction below:

1400kH 1/4 wavelength = 54m 3m cable radiation efficiency -21dB 1m cable radiation efficiency -31dB 150mm cable radiation efficiency -47dB

[Robin Prater]

Have you checked that you have a good earth!

A good engineering earth (4ft copper rod in ground) can cure a lot of problems and may improve SW reception.

Robin

[usenet]

I'm sure I have! :-) However how does one find one that's better except by trial and error which might be rather time consuming and expensive. I'm quite happy to change power supplies if I *know* the replacement is 'cleaner'.

[usenet]

Since it generates the noise even whe the system is powered down I can't imagine that any BIOS options will have any effect. (always assuming this was meant seriously!)