[Towertalk] IS Boom length the HOLY GRAIL ?

[Jon Ogden]

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
> 
> 
> 
> 
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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."