Tom,....As in most real-life situations my tower and antenna are a
compromise. I live in an environmentally concience community and I'm
attempting to keep a low-profile in my neighborhood. My C4-XL when fully
cranked up on the LM-470 ( see WH6H at QRZ.com) enables me to put out a
competitive signal ( four ARRL DX Phone plaques in five years) and although
I'd love to have stacked arrays and numerous 100' towers like at my friend
KH7R's QTH, the 2 el mono banders "stacked" on a single boom from 10 to 40 m
works ok for me. Having worked in the satellite comunications network
business for 28 years, I've become more interested in performance than
theory and engineering compromise is often necessary. God bless all of you
who have the 20 acres, 150' towers and stacked array's. While your out
mowing, climbing towers to "keep it up", I'll be at the beach or up on 10
meters with a European pile-up.
73's and Aloha,
Stu -- WH6H
n4kg@juno.com wrote:
> On Mon, 04 Feb 2002 Stuart Browne <satcom@lava.net> writes:
> >
> > no...but the performance of the C4XL is outstanding.
> >
> > Stu -- WH6H
> >
>
> So, you are basically testifying that a 2L Yagi with 4+ dBd gain
> is an outstanding performer, which I don't dispute.
> (I'm happy with my 'shortie' 2L40).
>
> To get 2 more dB over a 2L Yagi, one needs to go to wide spaced
> 3L Yagi's on 0.35 WL booms (24 ft on 20M), or a C31XR, or stack
> a pair of 2L Yagi's. ($$)
>
> To get yet 2 more dB, one needs to go to 5L or 6L Yagi's
> on 0.75 WL Booms or go to a 4 high stack of 2L Yagi's,
> for EACH band. ($$$$)
>
> It would seem that large *trapped* Tribanders potentially fall
> somewhere between a short boom full size 2L Yagi and good 3L
> Yagi's which is in fact about where the TH7 gains are from Roger Cox's
> measurements (except on 10M where the standard dimensions
> are optimized for 10M FM). (10M DX dimensions recommended)
>
> In other words, one needs to go to a MUCH larger antenna system
> to realize any significant improvement in gain over a full size 2L Yagi
> ...
> (or a 'multi-monobander set of 2L Yagi's), AND the full size 2L
> Yagi's have better bandwidth than most trapped Yagi's, especially
> the short boom single DE versions.
>
> The only advantage of larger trapped tribanders would seem
> to be in greater F/B ratio which may or may not be useful,
> depending on one's application (I prefer low F/B for contesting
> from south central USA) and one's local noise environment.
>
> No wonder the familiar Trapped Tribander designs are falling from
> favor. There still is one useful place for trapped elements and that
> is in directors to break up undesired effects of longer elements.
>
> The CC X7 is an example of an alternative modern design utilizing
> a Log Cell DE, full size reflectors and a single trapped Director.
>
> The 'open sleeve' trapped 15/20 DE with separate 10M close
> coupled driven elements is another interesting use of traps
> such as in the HyGain Explorer Tribander. Separate full
> size reflectors would enhance the performance of this antenna,
> or at least a separate 10M reflector.
> (An A4 with an open sleeve DE...)
>
> Actually, I expect one would find that a full size,
> horizontal DIPOLE, mounted on a tower, in the clear,
> with a ROTOR, is also a reasonably good performer,
> benefiting from efficient ground reflection due to horizontal
> polarization with NO sloping (inverted V) elements,
> being in the clear, and rotatable. The CC D3W trapped
> dipole is very popular and effective on the (narrow) WARC bands.
>
> I would say that MODELING has certainly improved our
> understanding of antenna performance and provided us
> with better choices in today's marketplace.
>
> Tom N4KG
>
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