In a message yesterday I mentioned that the ARRL RFI book referred to these
devices as a possible solution for RFI caused by the peripheral connections
of a computer.
After reading that, and finding a reference to Spectrum Control, Inc.
filtered connectors in the Mouser catalogue, I went to SCI's excellent web
site and researched the characteristics of these devices. So far as I can
determine, none of the units they make have very much attenuation at low to
medium HF frequencies. Their most aggressive filter has only 10 dB
attenuation at 5 MHz, rising to 30 dB at 50 MHz. Their target seems to be
RFI at television and V/UHF frequencies, rather than HF.
I also received a private e-mail from a subscriber explaining that video
signals will be adversely affected by any direct filtration that would have
any useful effect at low HF. I'm bccing him on this message, and perhaps
he'll repost that explanation for the general audience, because I think it
would be of wider interest.
73, Pete N4ZR
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