[TowerTalk] [Bulk] 80M and 160M Matching Network

[Bill Coleman]

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 at arrl.net
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901