In a message dated 11/18/02 5:46:32 PM Eastern Standard Time, stevek@jmr.com
writes:
> > > There are plenty of reasons why they are different, when you add them
> > up,
> > > there is enough reasons for serious operator to choose quad or
Quad-Yagi
> > > configurations. This is based on real 2m modeling and measurements.
> > > (K3BU)
> >
> > //The "Quagi" designed by N6NB 25 years ago as a hybrid quad-yagi was
> > derived exactly that way: Modeling on 2m, using loop elements and linear
> > elements and combinations thereof until the best results were achieved.
> > Those studies indicated that beyond the reflector and DE, additional loop
> > elements provided no better results by any measurement than linear
> > elements did, which is why the final Quagi design used loops for the REF
&
> > DE, and linear elements for all directors....... snip>>
VE3BMV designed Razor (Quad/Yagi) beams on 2m antenna range 30 years ago and
optimized them for best pattern (F/B, F/S) - gain compromise and 50 ohm
impedance. The best quad design is 3 el. Some of the "rules" I came across
are that max performance is produced with Quad antenna having one parasitic
element on the front and one behind the driven element (or cell).
So the reasonable Quad antenna would have 3 or 4 Quad elements. Beyond that
more improvement is gained by using Yagi parasitic elements.
Log cell makes significant improvement in long Razors, cleaner pattern.
Quads can be built to last, just like or better than Yagis, done it.
Quads have unique opportunity to take advantage of polarization and angle
steering (work in progress).
They are a bit awkward to handle, but having tower without guy wires
eliminates the problem.
My Razors outperformed stacked arrays at old W2PV, proof in contest results
and many times hearing pileups of Eu stations that W2PV was not responding to.
Recently I tried to "verify" my 3el. Quad design in the EZNEC and also run it
through AO. They came with slightly different dimensions. So far I had no
opportunity to get back my test range and to try to correlate the results or
"debug" it. I hope to be able to do that soon.
It is interesting that those who had quads and were able to use them, do not
dump on them. Mostly theoretitians do that based on software "wisdom".
K9LA did some analysis between 2 el. Quad and Yagi in Antenna Compendium #4
and shows slight gain and angle advantages even in software models.
Yuri, K3BU, VE3BMV
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