[TowerTalk] Modeling over ground was: Re: H frame for 10 or 15m

[Jay Kesterson K0GU]

On 8/16/2011 8:35 AM, Pete Smith wrote:
> I agree that the azimuth pattern will be the same, but the elevation
> pattern will be quite different, and to my mind is a lot more
> important.  We're not doing EME here.  For example, if I model against
> ground, and put the antennas at heights of 50 and 100 feet, my 14 MHz
> vertical pattern is very broad and clean, with no second lobe below 35
> degrees or so.  If I select only the lower antenna in the 50/100 stack,
> the clean main lobe moves up from 12 to 20 degrees, which can be a very
> useful capability late in an opening.

   You won't get any argument from me. Wave angle diversity is always a 
good thing. The guy wanted to know about 4x H-Frame (box) array spacing 
so I provided some data.

   But not everyone can have a 100 foot tower. If one only has a modest 
height tower the 10m yagi box (24 foot booms) is a good way to get as 
much gain as possible without building a 100 foot boom yagi or two 48 
foot boom yagis stacked vertically. Although building, installing, 
turning (or keeping it from turning) and maintaining a ~25' x ~25' 10m 
H-Frame array is not a trivial endeavor.

   My main focus is six meters. Until recently (down after 10 years for 
a rebuild) I had a four 7 el yagi H-Frame array. I also have a 9 el yagi 
on a 40 foot boom and a 7 el yagi at different heights. The 4 yagi array 
was my main weapon but I always have something else at various heights 
with larger azimuth beam widths available.

   Another poster in the thread considers the wider azimuth beam width 
of the vertical stack an advantage. I like the narrow front lobe of the 
box array. I can move the antenna closer to the direction of QRN sources 
and not hear the QRN as the QRN is just outside the main lobe. Also from 
Colorado I can point the array at Europe and pretty much get rid of the 
east coast and Midwest. It's all about what you want your antenna to do.

73,  Jay  K0GU