I have watched this thread with great interest along with the
8 element array discussion. I am curious as to how well a
simple separated winding or even bifilar for that matter,
transformer would work compared to the larger common
mode chokes. I have very successfully used broadband
transformers on each end of the nearly 1/2 wave resonant
connecting lines on my 8 element arrays for common mode
reduction. Very similar to a Beverage antenna needing
separate windings.
Even if the active antenna requires carrying DC on the coax,
a transformer can be paralleled with high Q inductors,
preserving the common mode rejection. Greg, ZL3IX
published his schematic showing this technique in 2004
which he used in his remote 8 element RX array.
Some of the enhanced techniques used by W8JI for
high common mode rejection transformers on flag and loop
antennas should even help with a transformer inserted in a
receiver feedline.
Lee K7TJR OR
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