> Give me the Force 12 antenna for simplicity, strength and light
> weight.
>You're welcome to your savings of 1/2 square foot and 10 pounds for the C3
over the 3 element SteppIR. In return, you give up
1 - 2 dB on 20/15/10, 3 dB on 17/12 (as well as a proper match), operation
on 6 meters ... as well as good F/R on 20-12.
That's why I am building a stack. Also, I rarely use 17/12/6 so that is not
a significant compromise for me.
And to you, I sincerely hope you never have any failure of a moving part
with your SetppIR.
Keith
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Joe Subich, K4IK
Sent: Tuesday, June 22, 2004 7:53 PM
To: keith@dutson.net; Towertalk@contesting.com
Subject: RE: [TowerTalk] HF LOG-PERIODIC ANTENNAS Comments Please
> From: Keith Dutson
>
> Your SteppIR must have the complicated matching network to work for
> all bands since element positioning is a compromise with the design.
> This network is lossy.
In fact, the SteppIR does not need a complicated and lossy matching network.
A matching network, other than a combined un-un/balun is not needed since
the proper tuning naturally matches the antenna.
> By contrast, a Force 12 multi-monoband has no such compromise and no
> associated loss.
You have obviously not modeled any "multi-monoband" antenna and observed the
significant tuning compromises that are necessary in order to achieve usable
SWR on all bands. I have looked at several commercial designs and by simply
removing the elements for the "other" bands the antenna can be made to
provide significantly more gain (at least one dB) or better front to rear
rejection (at least 5 dB at the design frequency).
Multi-monoband designs are the height of compromise where the infinitely
adjustable antenna is, by it's very nature, capable of being optimally tuned
at any operating frequency.
So long as the elements are tuned properly for their position in the yagi,
the absolute position is relatively uncritical.
For a given boom length, so long as there are enough elements to maintain
the required level of inter-element coupling, the gain does not vary
significantly with the position of the "inner elements" (elements between
reflector and last director).
Front to rear rejection and bandwidth will be effected ... but as long as
the inner elements are not tightly "bunched" at either
end of the boom, F/R is reasonably consistent (+/- 5 dB).
SWR bandwidth is a function of the amount of coupling among elements and
element tuning ... and in an infinitely adjustable antenna are not critical
to the overall performance.
> Give me the Force 12 antenna for simplicity, strength and light
> weight.
You're welcome to your savings of 1/2 square foot and 10 pounds for the C3
over the 3 element SteppIR. In return, you give up
1 - 2 dB on 20/15/10, 3 dB on 17/12 (as well as a proper match), operation
on 6 meters ... as well as good F/R on 20-12.
73,
... Joe, K4IK
_______________________________________________
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.
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_______________________________________________
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
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