I have a friend that wanted a small yagi for 10m and wanted direct feed
with no beta or gamma feed for simplicity.
I found some old Hygain element to boom clamps I had as surplus.
To make a long story short, I didn't have any of the Hygain insulators so I
tried, as an experiment, just a rubber sleeve, about 1/8 inch thick to
insulate the driven element from the clamp. In testing, the resonance was
way to high (200khz) from basic modeling I did, and impedance was more than
100 ohms. Modeling showed should be close to 50 ohms.
Question is, do you think I introduced series capacitance to the dipole,
raising the freq? This is all I could think of, since the Hygain insulators
have a fairly thick spacing between the element and the clamp.
73 Doug N4IJ
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