I'm looking for some feedback on an idea that I have for feeding a Shortened
40m
Rotatable Dipole.
I now have mechanical construction data (i.e. element taper schedule) for the
aluminum tubing that I have on hand that will yield a dipole element that
should
withstand the weather here in Northern Illinois. Thanks again to those
involved
for your invaluable assistance.
There are many ways to feed and match a shortened dipole element, such as
inductive center loading, inductive loading coils out some distance from the
center, linear loading, etc. All of these will work, each has it's advantages
and disadvantages. I am concerned about the mechanical aspects of these
methods, i.e. weight, weatherproofing, etc, and of ease of access of the
matching network for tuning. This dipole will be mounted about 10' or so above
my TH6, thereby making it a bit difficult to adjust.
So, here is my idea:
Feed the dipole with a short length (no more than 15') of SHIELDED balanced
line
made from two identical lengths of RG213. Any recent edition of the ARRL
Antenna Book describes such a line. Bring the end of this short run of
shielded
balanced line to a weatherproof box mounted on the tower. Inside this box will
be a balanced L-network or similiar, and a balun for 50 ohm coax feed to the
shack. An article by Rich Measures, AG6K, in Feb. 1990 QST details such a
matching network.
I'd appreciate any comments, pro or con, on this idea.
Thanks in advance,
Charlie N9CO ocker@chasind.com
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