[TowerTalk] Length of Inverted-L.

[john at kk9a.com]

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