I think, though, that it's definitely something to look into for the future.
We've had decades of work to develop tools and techniques for optimizing
conventional multielement beams, starting with essentially empirical cut and
try with rules of thumb, and now with very sophisticated (and accurate)
method of moments modeling and computer optimization, embodying those
decades of practical experience. I would say that it's no exaggeration to
say that one could use one of the modern Yagi-Uda design programs and crank
out a design, build it, and have it work within tenths of a dB of the
expectation. Certainly this is true for microwave antennas as well.
We need to create those same tools for other antenna configurations, and
phased arrays in their many forms are probably a good place to start. No
longer should the computational complexity be a reason to avoid particular
designs. Synthesizing and analyzing complex networks of 20 inductors and
capacitors would be impractical by hand, but is trivial for a computer. No
more must designers rely on the "cookbook" of matching networks. The key
will be acquiring and integrating the "practical experience" part. It's
pretty straightforward to create the models and optimize them, but real
antennas have real components in real environments, and people (we!) need to
start building and trying some of these designs to understand how to
integrate theory and practice.
One of the big hang-ups now is getting "good" measurements of "real
components" to put into the models. When you're building a 2-3 component
matching network, you can probably get away with simple approximations, and
just move the taps or turn the knobs until it works right and accept the
inevitable non-ideal behavior.
In particular, we need to understand the effects of environment on matching
components (it's one thing to analyze or measure a loading coil in
isolation, but what happens when it's 3 feet from a steel car body). What
about the effect of the house next to a physically small radiator like a
compact loop or loaded dipole/monopole? Fewer and fewer hams (particularly
the younger ones that we want to enter the activity) have the luxury of land
and towers without significant restrictions. Sophsticated and complex
systems have the potential to overcome a lot of the problems (albeit, not
all... nothing beats height and size!).
Jim, W6RMK
----- Original Message -----
From: "Robert Shohet" <kq2m@earthlink.net>
To: <towertalk@contesting.com>
Sent: Sunday, June 13, 2004 3:20 AM
Subject: Re: [TowerTalk] 80 4-square inside a 160 4-square? Pros and
Consplease!
> Hi Guys,
>
> I want to thank W8JI, N6RK, W5VU and Jim Lux (callsign?) for their
> responses. Apparently this can be done but due to technical issues, is
> rather
> complex. Having the need to use 2 antennas on 2 bands in an SO2R
> contest setup makes the possibility of an 80 4 square inside of a 160 4
> square, rather impractical.
>
> Back to the drawing board - thanks for all who responded!
>
> 73
> Bob KQ2M
>
> ----- Original Message -----
> From: "Rick Karlquist" <richard@karlquist.com>
> To: "Robert Shohet" <kq2m@earthlink.net>
> Cc: <towertalk@contesting.com>
> Sent: Thursday, June 10, 2004 9:04 PM
> Subject: Re: [TowerTalk] 80 4-square inside a 160 4-square? Pros and Cons
> please!
>
>
> > Robert Shohet said:
> > If I did this, then my existing 80 4 square
> > > (inv l's) would be inside the 160 4-square.
> > >
> > > I can't imagine this would be good for the 80 meter 4-square
> performance.
> > >
> > > Has anyone out there actually had an 80 4-square inside a 160
4-square
> > > and
> > > can tell me about actual changes in performance (that they have
> observed)
> > > of
> > > the 80 4-square and what they were?
> >
> > I have 80 and 40 meter concentric 7-hex arrays. The 80 meter
> > verticals have insulators at the midpoint with latching vacuum
> > relays across them. I have to open up the relays on the 80 meter
> > verticals when on 40 meters and also float them from ground.
> > Failure to do this would result in severe pattern distortion on
> > 40 meters. The same general principle should apply to concentric
> > 4 squares.
> >
> > > Are these problems (if any) worsened by using BOTH antennas at the
same
> > > time
> > > on different bands with two different radios? Both 4-squares would be
> >
> >
> > Difficult. You would have to use traps instead of relays.
> > The traps would act as loading coils on 80, so you would want
> > cancel the inductance with a series capacitance on 80. This will reduce
> > bandwidth, which is one reason why I don't do it that way.
> >
> > Rick N6RK
> >
> >
>
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|