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> From: Steve Narducci <nw9g@netusa1.net>
> Subject: TopBand: Vertical antenna phasing
To: <topband@contesting.com>
> Date: Wed, 16 Jul 97 04:27:55 +0000
> Been looking at the butternut hf-2v with 160 meter add-on. This will cost
> a fortune.
And probably not work very well.
> BTW my 160 m wire inverted L , bent at 95 ft with 4 radials is working!!!
Hi Steve,
The key is in two areas.
One area is keeping the current UNIFORM in the vertical (that
requires top loading) and loading losses minimal (that requires a hat
so you can avoid all coils or lossy stubs).
The other area is in the ground system. Four radials are not enough.
Unless the radials are hundreds of feet in the air, ground losses
will be severe.
With a phased array, ground losses can become even more of a problem.
That's because element currents become higher in many phased arrays.
Absolutely the best phasing advice comes from articles like Roy
Lewallen's stuff in the Antenna Compendium. The stuff you will
read about using a power divider is non-sense. Phased arrays
require equal CURRENT (if the elements are equal sized) not equal
power for maximum F/B ratio. Since element impedances are not equal
in unidirectional arrays, that means the elements require different
power....not the same. Lewallen discusses this in depth, as does
Forest Gherke? K2BT.
I use a phased array where I feed a 40 meter dipole's vertical
feedline (about 90-100 ft vertical) as one element, and a 135 ft
tower as the second element. I get four different patterns and about
20 -30 dB front to back ratio with this system, so the elements can
be quite different and still work (although it's easier if they are
the same).
73, Tom W8JI
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Hello Steve and Tom,
All the above that Tom has posted is true. The above experts have lots
of technical experience and technical education. They also have tunnel vision
because most all 160m/80m antenna designs in the ARRL Ant Handbook and ON4UN's
Low Band DX book are no-compromise FULL-SIZE designs. I don't think the
majority of hams that operate on those bands have adequate space to install
a full set of radials and guyed 130 ft verticals. So the experts are really
not doing us a full service by continuing to preach that "trade-offs" won't
work -they will and I'd like to see the experts turn their attention to
designing smaller multiband 160m/80m antennas that can be phased to improve
ERP.
I thank them for what the '90s antenna books contain; because if you look
at what the '70s antenna books contain, they've come a long way baby!
Especially having EZNEC.
Since I'm real estate challenged, I'm using two Hygain 18HT towers (55 ft)
that I've centerloaded on 160m with a broadband (160m-40m) power combiner-
splitter that uses a resistor. You can find a schematic of it in the ARRL
Antenna Compendium, Vol 2, page 10.
My system is short/loaded with coils and contains 32 radials; but I manage
to put out a signal good enough to compete with the locals with shunt-fed
towers and even one local DXer with a full-size vertical. Even though my
F/B is low (abt 10-15 dB), I still have the advantage of reducing some back
side QRM/QRN with less than 1 dB difference in forward signal strength
according to my EZNEC models.
I've learned more about antennas from making my "lousy" antennas work than
I'd ever learned from just browsing the books and dreaming. So don't shy away
from trying multibanding/shorten phased verticals......Just because they're
not optimum, they do work.
Good luck with phasing multiband/shortened phased arrays.
73, Dick Sander -K5QY (these are my opinions and not those of my company)
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