[SCCC] Question on Tuning a Force 12 EF-240 Reflector ( 2 El - 40mtr Yagi )

[Leigh S. Jones, KR6X]

My simulation shows that if I take a "40 meter" dipole tuned for 6920 KHz at 
70 feet in height and move it instead to 78 feet in height it will be 
detuned to 6890 KHz.  So, actually, your experience makes pretty good sense. 
Maybe you should tune your antenna at 70 feet in height to get 6920 KHz.

----- Original Message ----- 
From: "Dennis Vernacchia" <n6ki73 at gmail.com>
To: <sccc at contesting.com>
Sent: Friday, June 26, 2009 10:05 AM
Subject: [SCCC] Question on Tuning a Force 12 EF-240 Reflector ( 2 El - 
40mtr Yagi )


>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
> input.
> ( 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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