Top loading is a winner to increase antenna efficiency. I agree that
EZNEC is essential since umbrella (slanted) wires have less effect than
a flat top hat and also tend to shield the antenna a bit. The model
needs the segments aligned in each element. Trig or use AutoEZ to
figure that out.
There are a couple of articles worth reading on Rudy Severns web site
antennasbyn6lf.com
This article is for top loaded verticals for the new LF bands but covers
the principles well
http://rudys.typepad.com/files/chapter-3--1.pdf
My T is 10' at the base elevated radials, 85' to the top, and 33' or so
each side, resonates at 1820, 25 ohms.
Grant KZ1W
On 2/3/2018 17:44 PM, Richard (Rick) Karlquist wrote:
You should really model this on EZNEC.
Having done this many times, I can say
that the length of the vertical plus the
length of one of the top wires should be
about 120 feet to hit exact 1830 resonance
without a loading coil. However,
there is absolutely no compelling reason why
this is necessary. A loading/matching coil
is far more convenient if you keep the wire
length to 25 feet. Therefore, it should
never be necessary to put it up and down a
bunch of times to get it "just right". There
is no "just right" with respect to the antenna
proper. Use the taps on the coil to do the trimming
to make the system just right. This has been
discussed many times on this reflector.
Rick N6RK
On 2/3/2018 5:20 PM, Bill via TowerTalk wrote:
Planning on putting up a 160 vertical, but of course a 1/4 wave
vertical is out of the question here in HI since we have a height
limitation.
Here's the question: I'm putting up around 50 feet of 3 inch
aluminum tubing (left over from various antenna takedowns). I plan
on putting up on top of that around another 10 or 15 feet of smaller
diameter stinger for a total height of around 60-65 feet. I
obviously need to make up for the lack of height and I was planning
on making a top hat of four wires coming down from the top of the
antenna at around a 45 degree angle. The problem is how long to make
each of those wires. My guess is around 25 feet based on my past
experience in making Tee-topped 80 meter verticals. However, it is
only a guess and I don't feel like yanking the 3 inch pipe up and
down a bunch of times to get it just right.
I know some trimming will be necessary since this is not an exact
science. I just need an educated guess for where to start with the
length. Any ideas?
Bill K4XS/KH7XS
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