On Fri, 10 Apr 1998, Dick Green wrote:
> For all intents, then, can't we assume that the inverted V has an
> omnidirectional pattern?
>
> Also, if you compare an inverted V with a dipole that's less than 1/2
> wavelength high, isn't it pretty much a wash? That's what I figured when I
> opted to make my 60' high 80M antenna an inverted V instead of a dipole
> (easier to raise, easier to match, and no worse than a 60' high dipole on
> 80M.)
>
> 73, Dick, WC1M
Actually, the pattern for a Vee is an oval, with some few dB down off the
ends, but less down than a dipole. For any given peak height, the Vee
will be more circular than a dipole, but even at a quarter weavelength up,
the dipole and Vee will still show some oval-izing. When the oval become
circular enough to think of it as a circle for operating purposes is a
matter of judgment and experience at a given site. These notes are
predicated on level ground with no obstructions. Your forest may change
the exact pattern if the antenna is below tree-top level.
Whether I am using a dipole or a Vee, if I am given some choices as to the
direction of the run, then I would broadside the antenna to the most
desired directions. If there are no choices, then--as always with ham
antennas--I wopuld do the best I can with what I have.
There are some patterns for center-fed antennas at 35' and 50' up at my
site in one of the articles for Low Down (Antennas From the Ground Up
series) on the 135' doublet--and some
other notes on what happens when you droop or zig-zag a dipole in another
article--all based on modeling, which does NOT account for local building
and vegetation clutter--hence, they are only first order expectation
analyses.
Interestingly, as you lower the take-off angle of interest, even low
antennas show narrower patterns off the wire ends. Hence, it may pay to
look at both Vees and dipoles from the perspective of the range of angles
of interest as well as at the elevation angle of max radiation--which at
1/4 wl and lower is usually straight up.
Hope this is useful.
-73-
LB, W4RNL
L. B. Cebik, W4RNL /\ /\ * / / / (Off)(423) 974-7215
1434 High Mesa Drive / \/ \/\ ----/\--- (Hm) (423) 938-6335
Knoxville, Tennessee /\ \ \ \ / / || / (FAX)(423) 974-3509
37938-4443 USA / \ \ \ \ || cebik@utk.edu
URL: http://funnelweb.utcc.utk.edu/~cebik/radio.html
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