On May 1, 2011, at 10:29 AM, Gary Slagel wrote:
>
> I've got a used HyTower vertical I'm putting up. Its got the 160M coil at
> the base but I don't care for that system for 160 because you have to
> manually switch between 160 and 80.
>
> After reading Bill/AA4LR's email below and looking at his blog about the
> shunt fed tower I thought the switchable LC network at the base of his shunt
> fed tower is just what I need!
>
> Is there a commercially available, switchable matching device that I could
> use at the base of the HyTower that will allow me to switch from 160M to 80M
> without running out to the base of the tower to switch it? Something capable
> of handling a KW would be great but something smaller would be good to.
>
> Thanks for your help!
I haven't seen anything commercial for this type of configuration, Seems like
you could get a couple of high-power tuners and do the same kind of thing. I
think Ten-Tec made a high-power reversible L-network tuner at one point.
For switching, I use a large open-frame relay. Use a DPDT relay and disconnect
both ends (shunt and coax) of the network. With the complex impedances
involved, you may find that high voltages are present on the shunt.
I don't think my power limitations are the switching, but my coils. The T200-2
cores make for a compact, high-inductance coil with very little loss. (roughly
40 and 70 uH, for 80 and 160m, respectively) Solenoidal air-wound coils would
do better, but they would be huge.
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@arrl.net
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901
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