[TowerTalk] Trimming F12 240/340N elements

[James C. Hall, MD]

Hi Billy:

Thanks for chiming in ! :) I believe it is a 50 foot run of RG8X. I can get
the element higher, but only to about 40 feet. I'll definitely add guying !!

Billy, this is part of the new MAG we talked about.

73, Jamie
WB4YDL

-----Original Message-----
From: Billy Cox [mailto:aa4nu at ix.netcom.com] 
Sent: Monday, October 19, 2009 5:23 PM
To: James C. Hall,MD
Subject: Re: [TowerTalk] Trimming F12 240/340N elements

What length of coax are you
using between the feedpoint
and the meter on the ground?

That might be part of it ...

73/bc/NU

-----Original Message-----
>From: "James C. Hall, MD" <heartd0c at nwtcc.com>
>Sent: Oct 19, 2009 5:53 PM
>To: towertalk at contesting.com
>Subject: [TowerTalk] Trimming F12 240/340N elements
>
>Hello TT:
>
> 
>
>Does anyone here have experience with trimming the element lengths of the
>driver and/or director of the F12 240/340N ? I have the 3 element version
>and each element starts out the same length as the reflector with tips of
>38.5". With coax and balun attached, I am to raise each element as a dipole
>and trim the driver and director to the correct frequency. I first started
>with the reflector to verify that the frequency of 6.90 MHz was correct.
>After mounting on a push up mast and raising to a height of 20 feet or so,
>my meter indicates a dip in SWR at 7.017 MHz - 117 kHz higher than
expected.
>It would seem that the reflector is about 6" too short on each end.
>
> 
>
>The instruction manual states that the element will shift upward in
>frequency about 15 kHz between 15' and 30'. Below this height there is too
>much ground coupling. I see the indicated 6.90 MHz at only 7' above ground.
>
> 
>
>Again does anyone have information on this process ?
>
> 
>
>73, Jamie
>
>WB4YDL
>
>
>
>
>
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