[Towertalk] Can my 40' tower be a 160m vertical?

[jperalta@tampabay.rr.com]

Aren't radials also needed to make the shunt fed tower work efficiently? If so 
what would be the correct length and how many for a respectable installation?

Julio, W4hy



> Jim:
> 
>      I agree with Phil's recommendations on Jeff's book.  You can get it
> from ARRL.  I based my Trylon 64's shunt feed on Jeff's design.  The key is
> to have something as a capacitive load at or near the tower top to make the
> tower appear electrically longer than it is physically.  Your Yagi/40M
> add-on ought to be a pretty good load.
> 
>      Many on this reflector would recommend modeling, but I'd say try it and
> let us all know.  The feed is nothing more than a wire from the bottom of
> the tower and connected near the top, keeping it a couple of feet away from
> the tower itself (I used PVC tubing as spacer material).  Then you feed the
> bottom of the wire through a variable transmitting cap of some fairly large
> value in series with the coax center; I keep the cap insulated from ground
> by mounting it in a plastic weather enclosure (a plastic shoe box from
> K-mart).  The coax shield gets connected to the tower legs and ground
> radials.  Tune the cap for min SWR and call CQ.
> 
>      BTW, the sloper might have an impact on your ability to shunt feed the
> tower.  If you can't get the tower to load, you might want to remove the
> sloper and try again.  (I haven't modeled this, so I'm guessing.)
> 
> GL es 73 de
> Gene Smar  AD3F
>