Re: Topband: 160m noise

[Ronald Gorski <R.Gorski@Astronautics.com>]

The most effective method, that I have tried, for minimizing common mode 
current on coax braid is to wind the coax in a single layer solenoid of 
sufficient inductance such that a common size variable capacitor (attached 
to the coax braid at both ends of the coil) can tune the coil to resonance. 
I first used this technique to eliminate 80m common mode interference to a 
TV receiver. I wound approximately 15 turns of coax near the receiver input 
and attached a small broadcast variable to the braid at both ends of the 
coil. As the capacitor was tuned through resonance, the interference went 
from severe to zero.
Ron N9AU
At 08:03 PM 11/10/04 -0500, Sinisa Hristov wrote:
> Jeff Maass wrote:
>
> >       So, who has *practical* advice of how to apply a choke
> >       for flag/pennant antennas? I've been winding 15-20 turns
> >       of RG8X in an FT240-77 core.
>
>
> With high imepdance antennas one needs much better
> chokes than with 50-Ohm antennas. I would recommend
> winding RG174 (or even smaller coax) on FT240-43.
> You must wind enough turns to position the parallel
> resonance of the choke near 1.8 MHz. You may need
> several attempts to get to the right design.
>
> Winding it without measuring it is pretty useless.
> I've described the method of measurement in another
> message on this reflector few minutes ago.
>
>
> 73,
>
> Sinisa  YT1NT, VE3EA
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