Hello fellows,
first of all thank you Dick and Peter for running all those simulations.
Again, I have learned a lot.
Refering to the last part of my second report (16.9.99 14.17) it is clear
that top loads are hardly a substitute for height. Even raising the
antenna
from 10 to 15 m increases radiation resistance more than even the largest
top load can do.<
This is probably the reason why the early German longwave stations, for
example in Nauen (starting in 1906) or Königs-Wusterhausen (1915) or the
stations of the OMEGA navigations system on 13 kHz used umbrella antennas.
If you compare, what is necessary to build a 10m high antenna with four
horizontal radials, you need four supporting poles of equal height (or
trees, a house or whatever in the right distance) besides the antenna mast.
The umbrella antenna consists of only one vertical mast, and the top load
wires can servce as supporting wires as well. So doubling the height of
that antenna, you need less material compared but have a much higher
efficiency, even with sloping top load wires.
By the way, I was able to confirm the theoretical results of Dick's and
Peter's simulations when I shortened my top load radials from 20m down to
10m.
Best 73
Geri, DK8KW (W1KW)
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