Not exactly. Having just read the piece on the F12 Web site about quads and
yagis, Tom points in a rather circumspect manner to some unnamed research.
He does correctly point out that the flaw in comparing, say a 2-el quad to a
2-el trapped yagi is that it ignores the inefficiency of the traps and the
gains that can be made by interlacing monoband elements at optimum spacing
vs. conventional trapped yagi design.
The interlacing of monoband elements is, however, basically what the spider
quads (Gem Quad and others) did to very dramatic effect. A two-element Gem
Quad (with zero boom length), for example, kicked butt over a three-element
tribander at the exact same location.
But Schiller doesn't exactly come to a conclusion, evidenced by his praise
of the Overbeck quagi and the final two sentences, the last of which is the
main deterrent to quad construction:
"The argument about quads and Yagis will likely continue for more decades.
One thing is for certain - the quad is a 3-dimensional structure, more
difficult to build, erect and maintain than a Yagi."
Without assaulting Tom's integrity in any way, I think it is reasonable to
point out that the core raison d'etre (and rightly so) for the F12 Web site
is to market F12 antennas, none of which are quads. I suspect that a quad
manufacturer could use the same research in support of its products as well.
Yagis are easier to build, yet a one-element quad loop does have gain over a
dipole, which is essentially what a driven element in a yagi is. I suspect
that if you start with an element that has gain already, the resulting
multi-element antenna will also have more gain.
Yagis are also more aesthetically tolerable. So there are a number of
reasons to opt for yagi design over quads. But like Tom says, the debate
over performance will go on.
Tom is right, it should be noted, in suggesting that a C3S would, for a
variety of reasons, be a better choice than a spider quad or boomed quad.
73, kelly
ve4xt
----- Original Message -----
From: "Jon Ogden" <na9d@speakeasy.net>
To: "xppq" <xppq@pyramid.net>; <towertalk@contesting.com>
Sent: Friday, November 15, 2002 11:26 PM
Subject: Re: [Towertalk] IS Boom length the HOLY GRAIL ?
> I totally question the veracity of anyone that claims a cubical quad with
> the exact same dimensions as a yagi has more gain. It's just not true.
> Force 12 dispels this myth on their website.
>
> 73,
>
> Jon
> NA9D
>
> on 11/15/02 10:03 PM, xppq at xppq@pyramid.net wrote:
>
> > Below in a communication from CHUCK at Tennadyne
> > I am soon to install a T 620 - his is a 6 el LOG YAGI for 20m only (
> > discontinued model)
> > on 27 foot boom - it has 4 el in LOG cell, and director and reflector.
> > It is NOT a big antenna and I expect it will survive my very windy
> > location - It will be approximately 100 ft above ground.
> > I have no wild expectations myself - if it compares
> > with monoband yagi on 30 foot boom - so be it !
> >
> > the text below is from Chuck at Tennadyne -
> > I welcome feedback from the Tower Talk BRAIN TRUST
> > on this matter:
> >
> > josh n7xm nevada
>
> --------------------------------------------------------------------------
----
> > --------------------------------
> >
> >
> >
> > Josh, in general, and within limitations, they're correct. One must,
however,
> > compare apples with apples, and not with oranges. Now, apply the
psychology
> > of all of this, don't forget that people will tend to tell you what they
> > want/need to believe. The Cubical Quad, for instance, has different
gain than
> > a Yagi given the same boom length. A 2-element Quad for instance, using
a
> > reflector and an 11 ft boom has 1.1 dB more gain than a 3-element Yagi
on a 20
> > ft boom (W2PV). The 3 element Quad with an 18 ft boom is another 1.24
dB
> > higher, how do the gurus explain that away? However, with the T620 you
start
> > with a 'driven element,' the Log-Cell itself, that has a gain of 6.3 dBd
while
> > the DE for a Yagi is 0.0 dBd. Ultimately, the LCY parasitics do not
yield
> > quite as much of an improvement over the DE as the parasitics of the
single
> > element do, but it's very close.
> >
> > In controlled measurements on our test range, when we had one, my LCY
with a
> > 31 ft boom came in .13 dB higher in forward gain than a 6-element Yagi
on an
> > 80 ft boom, the latter was a design straight from the ARRL Antenna Book
and
> > optimized for overall performance. There'll always be those that "know
> > better" and I wouldn't worry about the self-anointed antenna gurus, just
cream
> > 'em in the pileups and smile, as I did when I had my own T620 (31 ft
boom) at
> > 101 ft. I've had too many engineers tell me that they were far too good
an
> > engineer to have made such a mistake............but they did. The test
range,
> > by the way, is a far more critical judge of an antenna than any
on-the-air
> > performance checks I've ever been part of.
> >
> > 73 Chuck - KA1PM
> > TENNADYNE
> >
> >
> >
> >
> > --- StripMime Report -- processed MIME parts ---
> > multipart/alternative
> > text/plain (text body -- kept)
> > text/html
> > ---
> > _______________________________________________
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> >
>
> -------------------------------------
> Jon Ogden
> NA9D (ex: KE9NA)
>
> Citizen of the People's Democratic Republik of Illinois
>
> Life Member: ARRL, NRA
> Member: AMSAT, DXCC
>
> http://www.qsl.net/na9d
>
> "A life lived in fear is a life half lived."
>
>
> _______________________________________________
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