On 8/15/2011 1:30 PM, Stein Roar LA6FJA-K3RAG wrote:
> Hi
>
> does anyone have ideas sizes for a H frame for 4-5 el yagies for 10 m and 15m
> ?
> is it 1/2 wl , 3/4 wl or 1 wl spacing ??
>
> I saw one from http://www.arraysolutions.com/Users/h2a.jpg Arraysollution
> from PY5EG
>
>
> 73 LA6FJA Rag
Your best bet if possible is to model the antennas and look at the
gain compared to one antenna and the patterns. The wider the horizontal
spacing the bigger your first side lobes. That may not be a problem if
you can't stack them very far apart horizontally. But if you can stack
them far apart then you need to possibly chose a bit more gain vs a
better pattern.
I have a model of a Hy-Gain 105CA (24' boom) for my antenna modeling
program. And I am a bit bored so here goes...
Just to get the feel for how the horizontal and vertical stacking
distance affects the antenna I first model only two antennas.
Single 105CA = 8.24 dbd
Two 105CAs stacked vertically spaced
20 feet = 10.50 dbd
24 feet = 10.84 dbd
28 feet = 11.12 dbd
32 feet = 11.30 dbd
36 feet = 11.35 dbd
As far as vertical spacing is concerned somewhere around 24-28 feet
looks pretty good. There is less interaction between the antennas as the
stacking distance gets larger. More than 28 feet produces little
advantage and a fair amount of extra wind load..
Two 105CAs stacked horizontally spaced
20 feet = 9.72 dbd (first side lobes are ~37 db down)
24 feet = 10.27 dbd (first side lobes are ~30 db down)
28 feet = 10.66 dbd (first side lobes are ~22 db down)
32 feet = 10.95 dbd (first side lobes are ~16 db down)
36 feet = 11.11dbd (first side lobes are ~16 db down)
This will depend on how much you value gain compared to pattern. I
would likely choose 28 feet vertically and 24 or 28 feet horizontally. I
like a nice tight pattern. Not a lot of advantage beyond 28 feet.
4x H-Frame array of 105CAs spaced
20' high - 20' wide = 12.00 dbd
20' high - 24' wide = 12.46 dbd
24' high - 24' wide = 12.71 dbd
28' high - 24' wide = 13.09 dbd
28' high - 28' wide = 13.53 dbd
The first azimuth side lobes are essentially the same value on the 4
stack as the 2 horizontal stack. This model is based on a 24 foot boom
10m yagi. A shorter boom will require a bit less spacing and a longer
boom more spacing.
73, Jay K0GU
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