Hi Jon;
Consider the full wave Quad has about 1.8 db more gain than a 1/2 wave Yagi.
The Quad is quieter on receive and does not hear rain static. The efficiency
of the average 3 el Quad is in the 90% + category. The 3 el Yagi is about
50%. Put 1000 watts on the Quad and you have apprx. 900 watts. Put 1000
watts on the same Yagi and you have aprrx 500 watts out. The power is lost
in resistive heat.
A few years ago Lew Mccoy W1ICP published an article in CQ magazine about
this. Boom length is gain, but there are other things that are more
important like, takeoff angle, frontal lobe pattern and so forth.
Bill Wall KC4UZ Antenna Mart
----- Original Message -----
From: "Jon Ogden" <na9d@speakeasy.net>
To: "xppq" <xppq@pyramid.net>; <towertalk@contesting.com>
Sent: Saturday, November 16, 2002 12:26 AM
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."
>
>
> _______________________________________________
> AN Wireless Self Supporting Towers at discounted prices,
> See http://www.mscomputer.com
>
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