Retuning the driven element with improve VSWR but you
may not have a good pattern on phone. I did some
experiments with my MonstIR where I tried QSY'ing with
just the driven element. Needless to say, the gain
suffered considerably. You still have a rotatable
dipole at least when you do this.
In terms of magic lengths of coax, the magic length
is 1 wavelength, about 100 feet of coax, right at
the bottom of your tower. The impedance at the
feedpoint will be duplicated at this magic point.
Now you can simply insert a series capacitor to retune.
About 100 to 200 pF should do it. Determine the right
tuning using small receiving capacitors and your
antenna analyzer, then when you have the right value,
replace it with a transmitting mica type. You can
install a switch or remote relay to short out the cap
for CW.
(Note: the magic coax length can be any multiple
of a half wavelength. Maybe 150 feet puts the
magic point right in your shack.
Rick N6RK
On 7/28/2012 5:20 AM, Richard Thorne wrote:
> I have a F12 2 Element shorty 40 beam mounted on my mast at 87'. The swr
> is setup per the manual, 2.0:1 swr points are between 7.0 and 7.14 as
> expected.
>
> I would like to operate the beam on LSB as well. Other than putting a
> tuner in line, are there any other options like some magic length of 75
> ohm coax for two swr dips.
>
> Thanks
>
> Rich - N5ZC
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