[Towertalk] IS Boom length the HOLY GRAIL ?

[xppq]

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

  =20


--- StripMime Report -- processed MIME parts ---
multipart/alternative
  text/plain (text body -- kept)
  text/html
---