On Wed, 21 Jul 2004 10:51:07 +0300, tj wrote:

What do you think? The element spacing would be fixed, is that ok?

oh1meq

Hi OM,

Certainly sounds ambitious. As for fixed spacing, you would be
sacrificing an optimal separation, but that would be the least of your
problems as you describe the design.

With 4m pipes the
distance of the upper and lower boom would vary from 1m (4m+1m+4m+1m=10m
band) to 6m (4m+6m+4m+6m=20m band).

This describes (I presume) three equal sized elements for either band
(and I would further presume, for bands in between too). What makes
one a director, one a fed element, or one a reflector? If they vary
independently to maintain those relationships; then being fixed top
and bottom by another boom may offer some problem. Then again, maybe
not, it isn't that much different and the two booms would only pull
slightly together.

As for the rectangular shape for the 10M band, that is a very
different feed Z than the more square shaped on at 20M.

You are going to need modeling to be able to find the separations of
the elements that work over these frequencies as well as to find the
feed point Zs. The rest are simply mechanics, which unfortunately may
be the easy part.

73's
Richard Clark, KB7QHC