Tom,
I've not modeled verticals but have fooled with them for over 40 years in
all kinds of configurations, from simple ground mounted verticals against
a radial field to phased arrays. My favorite arrangement was a 40 meter
ground plane that was about 70' high at the base. I started
experimenting with the R-7 in Moscow primarily because it was an
"innocent" looking enough antenna and didn't attract a lot of "official"
attention. It takes so many administrative approvals to erect an antenna
in Moscow that I would still be waiting for all the approvals for a more
elaborate antenna. I installed the R-7 about 10' off the peak of a
galvanized metal roof at about 150' on my apartment building in Moscow.
After I gained access to the roof and made friends with the "roof guard",
I started putting up more antennas. The R-7 was consistently 1-2
S-units above a similarly mounted dipole and was only 1 S-unit below an
A3S also about 12' feet off the roof. More often than not, it was even
with the A3S or little discernible difference on 20CW.
I also used the R-7 at 35' on Radio Shack push-up masts in Colorado and
at 70' here in Florida. Direct comparisons on 40 meters favor my 402CD
at 75', but again not by much. The noise level is of course much less on
the 402CD. On 20, my TH-7 is 1 S-unit better, and 1-2 S-units on 15. 10
hasn't been open enough to really do any direct compares. All my
comparisons have been with EU or Asia, especially with a friend in
Poland.
Can't explain it, but the R-7 and the DX-77 perched on a Radio Shack
push-up mast work very well for what they are.
Jon Hamlet, W4ZW
Casey Key Island, Florida
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