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
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.
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.
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'.
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.
*Learn from your parents' mistakes - use birth control.
Dave Plowman firstname.lastname@example.org London SW 12
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.
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
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
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
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