wrote
When I built my OWA's I used DX engineering insulated element mounts. With
these, the SWR curve of the real antenna matched the tapered NEC2 model
perfectly. I didn't even need to adjust the length of the driven element.


Tor:
Thanks for the reply. I've used home-brew plates and u-bolts for a
couple of
3 and 4 element 10M antennas, but all were grounded. The gamma match that
was
spit out by the YA program worked as calculated, and within the limits of
the equipment,
the measured VSWR curves matched the model.
While the subject line said "Hygain element clamps", I also have a box
full of Wilson
element clamps, both are close in appearance, but the Wilson clamps are
about
15-20% larger than the Hygain of the same element size.
First runs on an OWA for 10M used 3/4, 5/8, and 1/2 in. tubing, with a
bushing in the
element clamp to bring it down to 3/4 size. I was looking for flat gain and
F/B curves,
close to 50 Ohm feed, and use on-hand parts. I came up with a couple of
models that
looked promising, but I'm now looking at using 1-1/4 to 7/8 taper elements
for the driven
and first director. Since my optimizer is me, I haven't run enough samples
to tell if that will
show any improvement. What I have seen is that if a design is poor, a small
change in
taper schedule, element length or element spacing will make a noticeable
change in the
model characteristics, usually bad.
Plans are for a single 10M OWA here in Memphis, to be followed by a
3-high stack
at the retirement Ponderosa. I have also looked at scaling up to 20M, where
a 3 inch
boom prevents using the clamp style mounts. Sooo, thanks for the post, and
I'll
see you on the bands.

Mike W5CHR
Memphis Tenn