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
> ---
> _______________________________________________
> AN Wireless Self Supporting Towers at discounted prices,
> See http://www.mscomputer.com
>
> Wireless Weather Stations now $349.95. Call Toll Free,
> 888-333-9041 for additional information.
> _______________________________________________
> Towertalk mailing list
> Towertalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
-------------------------------------
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."
|