[600MRG] RFI Noise, Need filters.

[sbjohnston at aol.com]

Seems odd that a linear supply was making noise... maybe the regulator was going into oscillation.  I've seen three terminal IC regulators in the 7805, 7815, 7915, etc series do that when the capacitors to ground on input and output were missing or of the wrong value.


In general, for low and medium-frequency noise suppression I've had some success adding three capacitors: across the AC line and from each side to ground.  I've been careful to use AC-line-rated capacitors.  They usually have the term "safety" in the description and are specifically rated in VAC, not just V.



https://www.digikey.com/products/en/capacitors/ceramic-capacitors/60?k=safety+capacitor&k=&pkeyword=safety+capacitor&pv2049=u10000pF&pv2049=u0.012%C2%B5F&pv2049=u0.015%C2%B5F&pv2049=u0.018%C2%B5F&pv2049=u0.02%C2%B5F&pv2049=u0.022%C2%B5F&pv2049=u0.03%C2%B5F&pv2049=u0.033%C2%B5F&pv2049=u0.047%C2%B5F&pv2049=u0.05%C2%B5F&pv2049=u0.056%C2%B5F&pv2049=u0.1%C2%B5F&sf=0&FV=ffe0003c&quantity=&ColumnSort=0&page=1&pageSize=25


 I've not found the ready-built filters to be any more effective (and often less-effective) than this technique - but of course I've only tried a few.  Maybe the capacitance and inductance were too low in the ones I tried.



 

Steve WD8DAS

sbjohnston at aol.com
http://www.wd8das.net/
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-----Original Message-----
From: Paul Signorelli <w0rw1 at msn.com>
To: 600MRG <600MRG at mailman.qth.net>
Sent: Fri, Nov 30, 2018 11:42 pm
Subject: [600MRG] RFI Noise, Need filters.



I have a lot of 630M RFI.
The latest culprit was found coming from an old Kepco JQE 0-25, Linear Power Supply.
I added 2 Sprague  AC Line feed through filters and that eliminated the noise.
Does any one have experience with line filters.
Which are best for 630 meters?
Here is a collection of them.
<https://www.rfparts.com/filters/filters-emi.html>;.
I am going to need more.
Paul    w0rw


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