Its an interesting thread. A few comments.
- Its all about gain. You don't care about F/B because if you can
consider these antennas, you are going to have beverages. And if you have
good beverages, you will essentially never listen on your TX antenna again -
except for certain specific circumstances.
- If you have negatively sloping terrain of ANY kind towards EU,
you need to HFTA model it. Not NEC antenna model it. You do NOT have to
have the specific data. You can create your own ray data to see what the
effect will be. You do NOT have to have the specific info to understand the
effect of that slope. Estimate it, and you will see the effect.
- 80M yagis are notoriously difficult to maintain, so personally,
with negative slope to EU, if budget and space are no object, I would do an
elevated 4 square - of 4 - 85 ft towers with the insulated adapter at the 20
foot level. Do 4 radials under each one and then lay out a full ground
screen (ala K3LR style) in the full square area of concern (essentially
under all area that has a radial on it). That way you really don't care
what your ground conductivity is.
Ed N1UR
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