I think you'll find that vertical angle distribution of the two
antennas is the major factor,
with terrain being the obvious uncontrollable issue.
90' is not a particularly good height for a 40m yagi. As you go up
from 67', the models
reflect a higher angle lobe popping out, with a reduction in energy
at lower angles.
This doesn't reverse until you get to 133' or so. As a result, you
should see the vertical
outperform the yagi, at distances beyond 5k miles or so, particularly
where you have
an over-water path.
Up in VT, I had a 2 el cushcraft 40, at 90'. I also had an
elevated ground plane located
400' away from it, at the same height. AND, I had a vertical
dipole, the top of which was
at 120'. This was over crappy New England rock soil. The
verticals out performed the
yagi, on anything over 4-5k miles. Sometimes by not a lot,
sometimes by 3-4 S units, in
an uncalibrated receiver. So maybe 15-20dB.
Improve the ground system to the west, perhaps you'll be surprised.
n2ea
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