On Thu,2/4/2016 12:48 PM, Wayne Kline wrote:
ONES who swear by them and ONES who swear AT them
It helps if you actually take the time to study and learn how verticals
work.
There are two tutorials on my website that address exactly that. One
focuses on 160M, the other asks (and answers) the question, "If I Can
Mount My HF Vertical On My Roof, Should I?"
As to the "near salt water" question -- two excellent engineers who have
studied these issues and built antennas at the water line or on the
beach and done real science with them are George Wallner, AA7JV and Tom
Schiller, N6BT. George is best known for half dozen or so expeditions
to light up rare islands, and putting out a great signal everywhere he
goes. Tom was the designer of the original Force 12 antennas and the
prime mover in Team Vertical, a small group of contesters that has made
a lot of noise with verticals on or near the beach. I would urge anyone
who really cares about this sort of operation to study their work very
carefully. Google is your friend.
The short answer is that the earth (including water) affects verticals
in two ways: 1) Something under the antenna must serve as a return for
antenna fields and current. The earth is lossy, so it burns TX power.
This is why we need radials -- they serve to shield the field from the
lossy earth, and to provide a low loss path return for fields and
current. 2) the earth in the far field reflects direct radiation from
the antenna, and the sum of direct and reflected waves in the far field
forms the vertical pattern. BOTH of these mechanisms are important, both
must be satisfied. Even on a beach, radials are VERY important.
If an antenna is OVER sea water, the water can serve as that return for
current and field IF we make a good connection to it. That's why W6OAT,
NI6T, and I were able to reliably work KC2IOV on 40M SSB from the South
Indian Ocean with her 100W marine radio loading the backstay of her sail
boat as she circumnavigated the earth. She coupled to the water with a
big metal plate in the water right under the antenna.
73, Jim K9YC
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