YES. IF you can get 1/4 WL (or more) then 30 to 60 radials is
beneficial. IF you are limited to 1/8 WL long radials, there is
virtually NO benefit above 15 radials.
Tom N4KG
On Thu, 26 Sep 2002 14:47:07 US/Eastern jperalta@tampabay.rr.com writes:
> 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
> >
>
>
>
>
> _______________________________________________
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