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Re: [RFI] PC Power Supply Noise

To: rfi@contesting.com
Subject: Re: [RFI] PC Power Supply Noise
From: Tim Groat <tcgroat@mesanetworks.net>
Date: Wed, 26 Dec 2007 15:27:20 -0700
List-post: <mailto:rfi@contesting.com>
I've also used this method, based on W0UN's recommendation that appeared 
many years ago on one of these contesting.com reflectors. Measure the 
clearances inside the supply first, because the filtered connectors can be 
found with either straight or right-angle output terminals, as well as in 
different case lengths. Select a style that fits for power supply, while 
allowing at least 1/4" (6mm) clearance to all other parts.

Another thing to consider is the filter's current rating. PC power supplies 
for the North American market aren't required to have power factor 
correction for their diode-capacitor input networks. The input current 
flows in narrow pulses of high amplitude, which means the power factor is 
very low and the RMS input current is much higher than Rated Watts/120V. I 
use filters rated for 6A or more, which really isn't over-kill for a 300W 
PC supply. A 3A filter over heats at full load.

--Tim (KR0U)

>Roger Parsons <ve3zi@yahoo.com>:
>All the supplies have an IEC connector, and I have
>found that in nearly every case, it is possible to
>replace this with one with a built-in filter. These
>are very commonly available at rallies and electronic
>junk outlets for a dollar or two. In my experience
>this leads to a complete cure - it is _much_ better
>than trying to put toroids round power leads and
>similar tricks. (In a few cases there is not enough
>clearance between the filter connector body and the
>pcb components.)

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