My experience was the same as Petes. I tuned for max f/b on a remote
signal from a signal generator. Looking up at my antenna at 65 feet, the
shorting bar for the reflector is about the length of the fiber glass
rod from the boom. The DE short bar is about 3 inches further than the
fiber glass bar length from the boom estimated. It seems to work fine.
73, Dan, N5AR
Pete Smith wrote:
> At 01:04 PM 6/26/2009, Dennis wrote:
>
>> Of course I need this antenna to work for Field Day so Murphy Strikes again
>> at the worst possible time ! )
>>
>
> In my personal experience, the dimensional control of the shorting
> bars for the EF-240 is so loose that it is unlikely dimensions from
> one installation will work at another, even at exactly the same
> height. There's also the question of how taut or loose the linear
> loading wires are, in case you want to add another variable.
>
> What I did here was to feed a weak signal source - my MFJ259B -to 3
> feet of wire about 300 feet from my EF-240S, using an RX antenna
> feedline. Then I changed the frequency of the MFJ and turned the
> antenna until I experimentally found the frequency of maximum F/B
> ratio. My first time around, it was too high, and by moving the MFJ
> to the bottom of the band I could determine that the pattern of the
> antenna actually reversed, as the reflector turned into a
> director. It took two adjustments to get maximum F/B at around 7025,
> but that's where it wound up, and I'm quite satisfied with the pattern.
>
> If you have a way of tilting the antenna down so you can get to the
> reflector shorting bars, I'm convinced this works better and takes
> less fussing than the "cookbook" method.
>
> 73, Pete N4ZR
>
>
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