Jim Brown wrote:
.
>
> Assuming that the "open wire line" in question has impedance on the order
> of several hundred ohms, what is needed for the application is a matching
> transformer of some sort with an impedance ratio of 4:1 or higher. In
> other owrds, a so-called "voltage balun" or "transmission line transformer
> of some sort. I suspect you'll find winding instructions in the ARRL
> Handbook. For a ferrite material, the only good choice in the US is Fair-
> Rite Products #61, which is widely available as a 2.4-inch o.d. toroid.
> This is often called FT240-61 by vendors who mark them up at 4X cost and
> sell them to hams.
> Jim Brown K9YC
Jim is exactly right. I use a stack of three 2.4 inch Fair-Rite #61 for
the 450 ohm balanced to 50 ohm balanced transformers I have at each
end of my 850 foot long open wire line. They work very well.
(There are also, of course, 50 ohm to 50 ohm baluns at each end.)
Rick N6RK
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