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R.F filter for telephone

tzitzikas

May 9, 2010
16
Joined
May 9, 2010
Messages
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hi i am radio amateur at 160m. the problem is that when i operate my transmitter the transmitter create interference to the telephone.
i am thinking to put a circuit at telephon's line. My first thought is to put capacitors (10nf) which will ground the r.f. signal what do you think about this. Do you have any better proposition? some one tell me to put one adsl filter.
 

Militoy

Aug 24, 2010
180
Joined
Aug 24, 2010
Messages
180
The cap will probably help - Center frequency on 160m is 1.9 MHz - so the reactance of a 10nF cap at that f would be 8.38 ohms - enough to damp a 600 ohm line of RFI fairly well. You might consider building a full trap though - adding a parallel inductor to sharply notch out interference throughout the full 160m band.
 

davenn

Moderator
Sep 5, 2009
14,081
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Sep 5, 2009
Messages
14,081
You may even find 2-3 turns of the phone cable through a clamp-on ferrite core
will do the trick. place the core on the cable right where it enters the phone

cheers
Dave
 
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