Want to make a small directional antenna in UHF bands- either a yagi
or HB9CV or ??? Want the elements to be less than .5 WL. Anyone know
how to center or end load elements so that width of antenna could
collapse down to half to two-thirds the normal .5 WL? Perhaps some
other antenna design would do it but element loading comes first to
mind. Goal is VSWR of 1.5, a FB of 10db or better and beam width of
+/- 20 to 30 degress. In the 900 mhz band would like to limit width
to say 3 to 4 inches versus the nominal 6+. Any thoughts or directions
to look? Thanks!

Hi,
the Moxon rectangle may really be the right solution. See
http://www.cebik.com/moxpage.html for more info and
http://www.cebik.com/moxgen.html for the formulae and a simple Basic
program.

BR from Ivan

Ron wrote:

The Moxen rectangle is still a little too large.

If it's really only a little too large, you might consider the earlier
VK2ABQ which is square rather than rectangular, and thus has a slightly
smaller turning circle. The performance isn't as good as the Moxon
shape, but it will fit into some spaces where the Moxon won't.

Any thoughts on just center loading the elements of a yagi? Anybody
ever tried or know how to calculate element lengths or required
inductance?

It has often been done. The method of choice now would be to decide how
long the elements and the boom can be, and then experiment with various
loading configurations using a modeling program. As the elements get
shorter, remember that (a) the losses increase, as in all loaded
antennas; and (b) the shortened elements no longer interact in quite the
same way as full-length elements do.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

Ron wrote:
"Want to make a small directional antenna in UHF bands---."

John Devoldere, ON4UN considers short elements on page 8-10 of "Low-Band
DXing". This is an ARRL publication and contains much valuable
information. Antennas scale to any wavelength. Reciprocity rules, so it
makes no difference if you want to transmit or receive except that
efficiency is more important for transmitting antennas, usually.

John Kraus, W8JK considers short dipoles on page 166 of "Antennas For
All Applications". This is a McGraw-Hill publication and worth every
penny it costs.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
John Kraus, W8JK considers short dipoles on page 166 of "Antennas For
All Applications". This is a McGraw-Hill publication and worth every
penny it costs.

Also available on the gray market in a "Low Price Edition".
--
73, Cecil http://www.qsl.net/w5dxp



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Also available on the gray market in a "Low Price Edition".

What does a low price edition on the gray market mean? Sounds like I could get
one cheap, just don't know how.

73 Gary N4AST