Scott wrote:
Might be interesting to someone out there....

I built a copy of the 432 Quagi (8 elements) that appeared in the 1988
ARRL Antenna Book. It has a "claimed" gain of 13 dBi (which, if I
remember right, is 10.8 dBd).

I didn't lament over getting all the elements within 1/128" of an inch
and it came out OK. The only place I needed to deviate fairly
significantly is that I needed to move the first director about 3"
forward of the original design to get a better match. I have no idea
what this will do to the radiation pattern. As designed, mine had a
best SWR of 2:1, causing the solid state final in the Yaesu 857 to
start shutting down such that I was getting about 6 or 7 Watts out
instead of 20. Moving the first director forward as noted got the SWR
to 1.2:1. Much as I would expect since a quad element at resonance is
about 60 Ohms I believe. Anyhow...

Good matching on a quagi depends on getting the loop length just
right... which in turn depends on using exactly the same insulated wire
as the original author. This becomes increasingly critical with
frequency, so at 432MHz .

Moving the first director, or bending the ends backward or forward in a
symmetrical V-shape, is a very common way of optimizing the impedance
matching. With most yagis it has very little effect on the gain and
forward lobe, though it may affect the F/B ratio.

Measured it on the antenna range today at our VHF group's
(http://www.nlrs.org) annual get-together. My antenna came in with a
9.6 dBd gain. I can live with that! It was only 0.3 dB below the
reference antenna, an 11 element Yagi.

Range measurements are the only way to find out if your antenna is
really delivering the claimed performance, and those seem like
reasonable numerical results.

Seems to have a very sharp pattern!

Welcome to the world of long yagis! If you think an 8-element is
"sharp", wait till you've built something really ambitious.

Anybody have experience with this type antenna? I was impressed enough
to think about giving the 222 version a try...

Quagis are OK, and easy to build, but nothing special compared to other
types of long yagi.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
VHF/UHF Long Yagi Workshop:
http://www.ifwtech.co.uk/g3sek/diy-yagi