[TowerTalk] Length of Inverted-L.

[Jim Thomson]

Date: Fri, 5 Oct 2018 11:11:39 -0400
From: N4ZR <n4zr at comcast.net>
To: TowerTalk <TowerTalk at contesting.com>
Subject: [TowerTalk] Length of Inverted-L.

<What to do when two respected references differ?? ON4UN's book assumes 
<an Inverted-L is always a quarter wave ~135 feet), while the ARRL 
<Antenna Book assumes 165-170 feet.? ON4UN mentions longer antennas to 
<increase feedpoint impedance, but doesn't seem to put much faith in that.

<Comments?

-- 

<73, Pete N4ZR

##  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