On Mon, 24 May 2010 04:10:10 -0700, Michael Baker wrote:
>One sure way to break any common connection to the other elements is
>to use a line isolator/ 1:1 in line with each elements feed line. There is
>NO common ground connection at that point. You have a balanced antenna
>element to start with and an unbalanced feed line so putting a balun in each
>line would make sense and with the feed impedance being about 100 ohms a
>matching transformer would be prudent and would save the matching problem
>unless you used a 1/4 wave 75 Ohm stub on each feed element. You would still
>have an unbalanced stub to a balanced load issue. Interesting conundrum.
The connundrum here is that words and phrases are being tossed around without
an understanding of their meaning.
At least one product sold as a ine isolator is nothing more than a common
mode choke, also known as a current balun. It is childs play to wind an
excellent common mode choke for 15-30MHz using nothing more than coax and one
or more #43 toroids. Guidelines for doing so are in my tutorial. Such a choke
looks like an open circuit to a common mode voltage and the very small loss
of the coax for signal going through the isolator. The impedance of the choke
is the impedance of the coax.
73,
Jim Brown K9YC
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