> Date: Mon, 11 May 1998 09:47:32 +0300
> From: Morel Grunberg <email@example.com>
> I have a very strong power line noise interference from 9 to 30MHz
> and I already tried all the usual solutions, with poor results.
> I wonder if bandpass filters ( like Dunestar or ICE ) can help reduce
> the overall wide band spectrum noise level. Please let me know if you
> have experience on this issue.
No, they won't help even a tiny bit. The filters in you receiver
already only pass a small slice of that noise, whatever is within the
IF filter bandwidth. In order to make a change, the external filter
would have to be more selective than your receiver's IF filter!
You might try an MFJ noise canceller, it is the best system available
for this type of problem. There have been reviews in QST and CQ
magazine.... ON4UN and others swear by them.
It is possible to build a device that does something similar with
digital processing for impulse noises (like lightning and power line
noise) ahead of the receiver WITHOUT needing a separate sense antenna
or phase adjustment, but I'm not sure I can entice anyone to build
one commercially. It is too complex to homebrew, and might be too
expensive to market to hams.
The phasing type unit might be your only solution, and the MFJ is by
far the best one available for HF.
73, Tom W8JI
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