Well, after fighting a single-core solution to the problem, I decided to
break it down into smaller bits.
The idea was to both obtain a good match and to decouple the transformer
from the feedline. In the original article this was accomplished by placing
the two windings on opposite sides of a toroid. However, I could never get
a decent match with the cores I had on hand.
I now have one small binocular core transformer, made from two small
toroids, that gives me a 1.2:1 match at 2 MHz when terminated with a 910 ohm
resistor. Then I wound a separate 1:1 transmission-line balun on another
small core and connected it to the
50-ohm side of the transformer. I still get 1.2:1 through the balun, so I
think I'll stop there.
The balun presents about 500 ohms reactance at 2 MHz, so should be plenty
adequate to decouple the transformer from the feedline.
Both units together are very light and small enough to fit into a plastic
35mm film container, so that's what I will use for a weather housing at the
loop feedpoint. Weather sealing with hot glue, then a couple coats of paint
for UV protection should finish the job.
Thanks to all who offered comments and suggestions during this exercise.
Like all useful exercises, this has been a learning experience :-)
73, Bob N6WG
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