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[RFI] rf current meter and ferrites

To: "rfi reflector" <rfi@contesting.com>
Subject: [RFI] rf current meter and ferrites
From: "Kostas Stamatis" <sv1dpi@otenet.gr>
Date: Tue, 22 Sep 2009 23:06:40 +0300
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
Some time ago i had asked for helping me to buy the appropriate ferrite for 
rfi.
So i bought some ferrites clamp on mix31 from mouser electronics
I don't know a way to recognise them but i suppose that Mouser sent what i 
had ordered.
I put them in some cables and i have not significant problems anymore
After all i searched it more and assembled this
http://www.ifwtech.co.uk/g3sek/clip-on/clip-on.htm
It is an rf current meter and i suppose that i could see rf coming with my 
coax and stops after ferrites.
Is this logic ok? If we have the chain ant-ferrites-rig then we must put the 
rf meter between rig and ferrites or between ferrites and ant to see the rf?
In one of my friends who had an rfi problem i put the ferrite and i saw 
smaller current between ant and ferrites and that's surprised me. I thought 
tha the difference is between rig and ferrites.
Another issue is this. I had some ferrites bought from a local store uknown 
type. My impression is that these ferrites did a worst job than mix 31. But 
when i measured with my homemade rf current meter (between rig and ferrites) 
i saw that the uknown ferrite does a better job than mix31 (my initial tests 
were at 7MHz and 21MHz where i had sometimes mini rfi problems). But in my 
adsl modem i replaced 10 uknown ferrites with 2 mix31 and i have no problem. 
I feel that i am doing somethin wrong but what?
Kostas sv1dpi

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