Excellent summary Jim. I have always used 135' of wire and either matched
it with a hairpin or lived with the elevated SWR. I am wondering what the
advantage is to using longer wire and adding capacitance from a signal
strength and bandwidth perspective? This method is probably easier to
adjust if using a vacuum variable. What are the suggested voltage and PF
vacuum variable capacitor specs for tuning a 170' top band inverted L?
John KK9A
From: "Jim Thomson"
Date: Fri, 5 Oct 2018 09:25:39
## 165-175 feet works good.... BUT you then requires some series C to
cancel out the XL
of the aprx now .375 long ant.
### ~135 feet may well result in less than 50 ohms. No big deal, a
helical
hair pin coil across the
feedpoint will increase the feed Z up to 50 ohms. But the ant has to
initially be a bit shorter to provide
for some XC. Its just a step up L network. Then you also have DC
grounded the ant as well.
And the ant is a lot shorter than a .375 ant.... which may well be easier to
install etc.
## A buddy used a motor driven vac cap in series with his 160m GP,
which
has a T top loaded
capacity hat.. sorta like an inverted vee on top..with the center
supported on
a catenary line between 2 x trees.
Then it tunes the entire band from 1800-2000. Fixed caps, or relay
switched
cap assy could also be used.
In his case, the vert portion is 100 ft tall..with the capacity hat T
also at
the 100 ft point, with sloping ends.
### But if u can only go up say 40-50 ft..... you might not want to go
horizontal for another 120 ft.... to make the
.375 ant... along with a series cap. You would end up with a substantial
Horz polarized component.
Jim VE7RF
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