[NLRS] HOME BREW A Cubical Quad for 432

[Gerald]

On Wed, 2005-05-04 at 09:29 -0500, christenson at charter.net wrote:
> 
> I have been looking for a calculator to build a multi element cubical quad for 432. What I mean by multi element is in the rang of 10 to 20. All I have found on line is 5 element calculators. 
> 
> I don't want any of the Yagi-Uda is better emails, or the Quad sucks emails.
> 
> Just looking for the element lengths and element spacing.
> 
> Thank You,
> 
> Kris (KC0REO)

You are not going to LIKE this response.

The main reason you don't find any design information for long quads is
that they don't work well. Even the 5 element has a strong 45 degree
cross polarized side lobe. Comes from the vertical element sections
(though with out of phase currents) coming up in phase at a distance at
the 45 degree angle. That wastes a significant part of the applied
energy and if mounted vertically polarized that cross polarized side
lobe injects a great deal of ground noise to the receiver.

You could try EZNEC or ELNEC to devise something better but you can't
get away from the cross polarized side lobes.

I don't have much better regard for the quagi, the weakest signals I've
heard from Cedar Rapids (100 miles from here) came from quagis.

There has been a ham pushing flattened quad elements at hamfests and the
Central States VHF conference. When tested on the CSVHF antenna range
they were almost matched dummy loads. The gain was far lower than a good
yagi on the same length boom. He went away grumbling that the testers
(who have been running the CSVHF antenna tests longer than he's been
alive) didn't know how to test.

There is a possibility of circular quad data as in the loop yagis used
so successfully at 902 to 2.4 GHz. The circular loops don't compute well
in any of the NEC or MiniNEC programs so they haven't yet been optimized
by computer. Their design information ought to be able to be scaled to
432 MHz. It may have, but if I've seen it, I don't remember where. The
circular loop yagis don't have the constant taper of the optimized yagi,
such as those based on DL6WU designs or the irregular taper of NBS
designs, both of which have been proven on antenna ranges and on the
air.

-- 
73, Jerry, K0CQ
Dr. Gerald N. Johnson, electrical engineer
All content copyright, Dr. Gerald N. Johnson