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Re: [TowerTalk] OCF mystery?

To: "VO1HP" <>, <>
Subject: Re: [TowerTalk] OCF mystery?
From: "Scott & Sherry Souva" <>
Reply-to: Scott & Sherry Souva <>
Date: Tue, 6 Dec 2011 21:52:33 -0500
List-post: <">>
Hi Frank,

Can you verify the balun is working correctly with an antenna analyzer (i.e. 
MFJ-259B)? If you don't have an analyzer, maybe you could borrow one from 
another ham? I recently hung a 254 foot near end fed wire (same as OCF?) and 
fed it at 20% from one end with a 4:1 balun. My situation is similar and it 
is hanging off my tower, but the balun is the high point of the antenna. My 
target was obviously 160 and 80 meters, and I have resonance at 1.90 MHz and 
3.75 MHz. There is an article in QEX this month that describes this type of 
antenna and the optimal feed point distance from the end of the wire.


-----Original Message----- 
From: VO1HP
Sent: Monday, December 05, 2011 4:05 PM
Subject: [TowerTalk] OCF mystery?

I am using a new Comtek 41130ET   4:1 balun  from  to build an 80-40-30
OCF dipole as per the data on the W8JI web page regarding ICF dipoles.
Primarily to use on those three bands....any other bands that it might
work on would be a bonus!

I am using 134 ft of #12  electricians solid copper wire (insulated) fed
at the 20% point or approx 27ft from one end.   The antenna is arranged
in Inverted Vee format.  The center of the wire is at 52ft and each end
is approx 17ft off the ground on posts.   Both legs are in approximately
the same vertical plane.  The balun is suspended in mid air in the
antenna leg to the south of my tower and the center of the wire is held
up by my  tower.

After some pruning the wire today the antenna has the following SWR
measured on a Drake WH7 wattmeter in my shack....Approx 150ft of 50ohm
cable length to the balun from the tx.

3.5     5:1   unacceptable
3.8     5:1   unacceptable
7.0     1:1   wow!
7.1     1.02:1   wow!
10.1   2.2 :1    acceptable
14.1   2:1         acceptable
18.1    4:1        unacceptable
21.1    3:1       acceptable
24.9    1.4 :1   wow!
28.0     1:1      wow!
28.5      1:1     wow!

Anyone have  any clues as to why the SWR on 3.5 and 3.8 is so high?.
The antenna is not useable on that band except for listening.  I do not
use antenna tuners and expect to operate all resonant atnennas.  I
expected 80M to be the best band in terms of SWR based on the info on
the W8JI website.   Could there be an issue with the balun.   Why does
the dipole appear to match the W8JI info more or less except on 80?

Mystified --  Please help

Frank VO1HP

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