I happen to have a top loaded vertical for 160 meters that is considerably
shorter than 1/4 wave.
I match this antenna by using a series coil followed by a shunt coil. The
values in my specific case are 15 uH for series and 2.7 uH for shunt.. This
brings the SWR values to 3:1 or less over the range 1800 to 1930 kHz. I use
3/4" CATV hard line as the feed line to my station so I am indifferent about
the losses in the feed line for such SWR. I use an edge wound coil using
5/16"x1/8 rectangular conductor for the 15 uH and #12 silvered on a ceramic
form for the 2.7 uH . Losses are relatively low and heat dissipation is
generally not a problem in Idaho during the winter for the network at the
base of the antenna.
Matching networks [switched] at the station bring the SWR into the 1.5:1
range for 40 kHz segments of the band starting at 1800 and going to 1920 or
so
YMMV.
Tod, KØTO
>
> This is an OK method, but it is somewhat clumsy to tune,
> especially if you don't have fractional turn resolution.
> Also, it assumes the vertical is base loaded. I have top
> loading wires on my vertical, so the input impedance is not
> necessarily capacitive, and this method doesn't apply.
>
> Rick N6RK
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