[TowerTalk] Common mode chockes

[Phil Clements]

Why don't you put a 75 to 50 ohm un-un transformer at the point
where the CATV-coax junction is. This will serve as a choke from
1-30 mhz, and your radio will see 50 ohms on all bands.

Beware of the Radio Works "line isolator." It is only a few turns
of standard RG-58U on a ferrite bar....good for only 320 watts or
so on 10m.

(((73)))
Phil, K5PC
"The Dark Ages were caused by a Y1K problem."



> In the course of troubleshooting my recent RFI problem, I discovered that
> putting a large coax coil - roughly 15 turns, 6-in diameter, of RG8X - at
> the shack end of my 75-ohm CATV feedline got rid of the last vestiges of
> RFI to my wife's computer when the 80-meter array is pointed toward the
> house.  The problem is that the addition totally changed the tuning of my
> amplifier on 40 meters and up, due presumably to the added line length
> transforming the impedance at the shack end to some new and creative values.
>
> I'm now considering a commercial line isolator, in the hope that it will
> control the common mode currents while not functioning (so much, anyway) as
> a series transformer. First, am I correct in this, as a general assumption?
>  Second, can anyone recommend a good commercial product that is effective
> at 80-meters.  Third, could I homebrew an appropriate choke with 50 or so
> #43 or #77 material beads on a length of teflon?
>
> 73, Pete Smith N4ZR
> n4zr@contesting.com
>
> Sometimes a tower is just a tower
>
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