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[TowerTalk] Question on Tuning a Force 12 EF-240 Reflector ( 2 El - 40 m

To: towertalk <>
Subject: [TowerTalk] Question on Tuning a Force 12 EF-240 Reflector ( 2 El - 40 mtr Yagi )
From: Dennis Vernacchia <>
Date: Fri, 26 Jun 2009 10:04:28 -0700
List-post: <">>
I recently acquired a NEW Force 12 EF-240 2 El 40 mtr Yagi.
( New Old Stock - Several Years old )

If I understood the instructions correctly, when one is adjusting
the antenna, one first tunes the Reflector element

one does this by hooking the F12 supplied balun to the Reflector Element
and leaves the Driven Element Open ( No connection to Driven )

At 1/2 wavelength height ( I have the antenna at about 79 ft height )
one adjusts the Linear Loading wire jumpers so that one sees a
dip at 6920 kHz ( John K6AM actually modeled the antenna with software
and his calcs came out to 6940 -  but he said no to worry, go with F12
recommended 6920 kHz )

Ok, so I set the jumper to 15 inches from the boom insulator support rod
and after many iterations I had to move the jumpers now 5 inches AWAY from
the Boom
and I am barely at 6910 kHz

Am I doing something wrong. ( Element length is fixed and not adjustable per
the riveting scheme )

It seems that having to move the Reflector linear loading jumpers 5 inches
from the factory recommended
initial settings is way too much adjustment and I still am not at 6920 kHz.

I have not adjusted the Driven Element yet and it as at teh factory
recommended settings of teh Linear :Loading
Jumpers and no balun or anything attached to it;s feedpoint.

Again antenna is up at 78 ft ....there is a 3 El SteppIR 8 feet below it and
the SteppIR's
elements are fully retracted so I find it hard to believe the SteppIR is
affecting my readings
since all the F12 EF-240 sees if at all is the metal boom of teh SteppIR
which is
paralell with the F12 Ef-240 Boom

If anyone recalls what his experience was tuning the EF-240 reflector and
what was final jumper
settings for an RF-240 at 1/2 wavelength high, I would appreciate your
( how many inches are your Reflector wire Jumper from Boom support insulator
? and did you
actually get the reflector to resomnate around 6920 kHz  ?)

Of course I need this antenna to work for Field Day so Murphy Strikes again
at the worst possible time ! )

73, Dennis N6KI

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