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TopBand: Common Mode Rejection Filter

To: <topband@contesting.com>
Subject: TopBand: Common Mode Rejection Filter
From: George.Guerin@kellogg.com (George Guerin)
Date: Tue, 3 Feb 1998 12:37:50 -0500
--IMA.Boundary.056725688
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     W8AV, Goose wrote:

""

I agree with Jim N4MXZ.  The common mode filter that he spoke of works great. 
I used two 75 ohm to 300 ohm  CATV transfromers and a 300 ohm TVI filter. 
Hook them up as follows:
     
 CATV IN  -  75/300 XFMR  -  300 OHM TVI FILTER  -  75/300 XFMR  - RCVR
     
That should do the trick.  The secret is that the filter breaks the shield so 
that the RF can not flow into the receiver on the shield of the CATV coax. 
Give it a try.
     
73......................de Goose W8AV  ""


Also, you may have to wind the TV feed line through a 
ferrite ring to help knock strong signals down as well.  

In today's world, a #2 or #6 mix ferrite core about 2 inched 
diameter makes a nice form for both the 75 ohm coax and the 
power cord to be wound through.  Some of the power supplies 
arrange the power cord as a TVI antenna and "detect" it via 
the rectifiers.

George, K8GG
--IMA.Boundary.056725688--

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