[Antennaware] Cubical Quad antenna model for VOACAP
k2xx at swva.net
Sun May 14 15:41:28 EDT 2006
Guy, I have recently modeled a two element 30/40M quad on a 20' boom
(0.205 and 0.142 lambda respectively) and got free space gains of
7.4-7.5 dBi. My design criteria were maximum gain and a reasonable
match to 100 ohms. How much gain are you observing for two and three
Guy Olinger, K2AV wrote:
>Modeling a single or 2 element quad and a dipole and 2 element yagi in
>free space shows the "why" of the difference. In the vertical plane
>bisecting the elements, a quad element squeezes the vertical whereas
>the dipole does not, and the 2 element yagi squeezes the vertical very
>little. That extra vertical squeeze by the quad elements is the basis
>for difference in gain of a 2 element quad and 2 element yagi. This
>advantage quickly disappears as the number of elements grows.
>A 2 element yagi's lack of suppression of the pattern straight up and
>straight down is why 2 element yagis don't do as well as expected in
>stacks unless *designed for* both the stack and height above ground.
>They interact heavily, even if one or the other is not fed. Bill's
>stated equivalence of a 2 element quad and 3 element yagi is easily
>confirmed in a model.
>Bill Tippett <btippett at alum.mit.edu> wrote:
>Tony, I think we are saying the same thing. A 3 el
>Yagi (on a 1.8 X 8' = 14.4' boom) should be very close
>to a 2 el Quad on an 8' boom. Regarding anecdotal
>comparisons, I would simply note that none of the
>large multi-multi stations use Quads above 80 meters
>(KC1XX, W3LPL, K3LR, K9NS, etc.). If there was really
>much difference, don't you think they might use Quads?
>Back to Don's original question, the model for a
>2 el Quad will not be that much different from the model
>for a 3 el Yagi supplied as a part of the HamCAP front-end
>for VOACAP. We're talking very minor differences which
>will be lost in the other VOACAP uncertainties.
>73, Bill W4ZV
>P.S. I built a 4 element monoband Quad for 20m in 1960.
>Scanned for viruses by Blue Coat
>Antennaware mailing list
>Antennaware at contesting.com
More information about the Antennaware