[TowerTalk] BP filters against power line noise

[Tom Rauch]

> Date:          Mon, 11 May 1998 09:47:32 +0300
> From:          Morel Grunberg <morel.grunberg@telrad.co.il>

> 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.  

Hi Morel,

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
w8ji.tom@MCIONE.com

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