In his 2 volume pair of books on Quads, Cebik shows that Quad efficiency
can be improved significantly by using 1/2 inch tubing conductors. He
looked at accomplishing the same improvement by using 2 wires in each
Quad element spaced several inches. These books also compare a 2 el quad
vs a 2 el Yagi and a 3 el Yagi for gain, F/B, and SWR while sweeping the
frequency across the 10m band. A lot of the information in his books is
available for free on his web page www.cebik.com Answers to all of the
questions discussed in this thread and much more is available there. 73,
Dan, N5AR
Michael Tope wrote:
>
> You can actually model the conductor losses in a Yagi (or quad for
> that matter) using NEC. You will find that the difference between
> aluminum tubing and a perfect conductor is typically a very small fraction
> of a dB. Its certainly not 3dB. In fact if anything the efficiency of
> a yagi is probably a bit better than a quad given the large surface
> area of the tubing relative to that of the wire that is usually used to
> build a quad.
>
> 73 de Mike, W4EF.................................................
>
> ----- Original Message -----
> From: "Bill Wall" <billwall@eyecon-solutions.com>
> To: "Jon Ogden" <na9d@speakeasy.net>; "xppq" <xppq@pyramid.net>;
> <towertalk@contesting.com>
> Sent: Saturday, November 16, 2002 4:51 AM
> Subject: Re: [Towertalk] IS Boom length the HOLY GRAIL ?
>
> > 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."
> > >
> > >
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> >
>
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>
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