I have been workling on some ideas for 160 transmitting antennas and need
some input.
I am in the process of finishing off putting Polyrod fiberglass cable and
Phillystran on my 40 meter tower. At 199.9 feet and 90 feet are KLM 4 el 40
meter beams. In the next month or so, I plan to install the six 6 6-element 10
meter beams on the same tower. When completed the tower will have the Polyrod
and Phillystran to around 15 feet of the anchors, leaving a virtually
'electrically clean' environment. All cables will come off pretty close to the
base of
the tower except for the 1 5/8 hardline which require a decent size bend at
the bottom. I also have room for most of the radials to be 130 feet or so...if
I annex my neightbor's unused land.
What I want to do is shunt feed the tower and have a system of 4 wires
suspended at right angles to each other to provide switchable
reflector/director
like I have seen in several publications. Getting the height and the distance
for the relectors/directors will not be too much of a problem. However, I am
concerned about the height of the tower being used as a radiator. A rough
guess
is that the top loading of the tower by the boom of the KLM 40 meter antenna
would make the tower around 230 feet or so. The boom is totally insulated
from the elements so I think the elements would have a relatively small effect
on
the total effective height.
I have two questions. First, is the 230 feet or so of effective height too
tall and and would I be at a disadvantage to a tower which had an effective
height of around 130 feet? I know the lobe changes as the height passes1/4
wavelength. Second, is a system of some elevated and some buried radials
fraught
with problems. I would like to elevate some of the radials to 10 or 15 feet.
Anyone who has been down this road or who has some ideas about this system?
Thanks for the help.
Bill K4XS
|