steve d wrote:
> I am curious as to what everyone here thinks along the lines of compact VHF+
> beams. I can't use the normal beams I have for VHF+ at the house because I
> can't put them outside and there isn't enough space to turn them in the
> attic.
>
> I have resorted to using my Cushcraft A270-10s for 2m/70cm and one of two
> wire HF antennas through a manual tuner and the auto tuner on my radio.
> Obviously the wire antennas are a pretty poor way to get on the band, but I
> have made contacts with them.
>
> I was looking at the hexbeam by wb3bel http://wb3bel.googlepages.com/ for 6m.
> I might be able to sqeeze something like that in the attic. What do you
> think?
>
> Another issue would be the proximity of the 2m/70cm beam. I might have to
> scrap that one in favor of 6m as I don't have the space to spread the
> antennas out. Would there be any way of incorporating 2m and 70cm in to one
> hexbeam without destroying the pattern/performence completely? I know that is
> like asking dirt to turn to gold but hey, Ill ask anyway HI!
>
> Steve, KC8QVO
>
>
>
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>
Steve,
If you look in the Cushcraft catalog you'll find that they make a
50/144/432 antenna which is a A270-10 mounted on the boom of a 6L yagi.
The 2M/70cm yagi is vertically polarized while the 6M is horizontal,
which seems kind of dumb until you try computer modeling the thing and
you find out that the 6M antenna really messes up the 2M/70cm antenna.
I've done some experimenting on the computer and you can put the 2M/70cm
on the boom of a 6M if the smaller beam is in front of the 6M elements
(which seems intuitive). If the 6M beam is a 2L (particularly if its a
driven+director instead of a driven+reflector) the overall boom is
pretty short. You could even make the 6M antenna a single driven
element out of wire supported inside a PVC tube (tnx K8MR), positioned
behind the A270-10 and be only slightly longer than the Cushcraft
antenna alone. Or, you could use a Moxon antenna for the 6M section -
Moxon elements are only about half as long as dipole/beam elements.
Above all, don't give away 2M capability. That will be your most
productive band. Then add 6M which *may* keep up with 2M is condx are
good. 432 is fun and usually there is decent activity, but I'd be
afraid that the roof boards and shingles might absorb a lot of RF at
432. No harm done, but the antenna performance will most likely be
hampered.
You should probably also do an RF exposure assessment (see the FCC
rules) if you're gonna run more than 10W (particularly on 432) with
antennas immediately over your head.
73,
Dave/K8CC
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