Re: [TowerTalk] Stacking Distance for M2'd 6m7JHV?

[Jim Lux <jimlux@earthlink.net>]

At 04:35 PM 7/12/2004 -0700, David O Hachadorian wrote:


> On Mon, 12 Jul 2004 15:02:34 -0500 "Chuck Dietz" <w5pr@swbell.net>
> writes:
> >  Spacing does not really affect takeoff angle.  Takeoff angle is
> > totally
> > dependent upon height above ground.  If you have optimum spacing,
> > the
> > takeoff angle will be the same as an antenna mounted 1/2 way between
> > the
> > stacked antennas.
> >
> > Chuck W5PR
> >
> >
> > May be, but I have always heard 1/2.  Anybody out there with
> > experience?
> > How does spacing affect take-off angle?
>
> You can download the free program YTAD, which helps to answer
> questions such as these at:
> http://www.arrl.org/qexfiles/
>
> The latest version of this program, apparently much improved,
> is called HFTA. I believe it comes on CD-ROM with purchase of
> the ARRL Antenna Book.
>
> Dave Hachadorian, K6LL
> Big Bear Lake, CA

It's not the average of the two antennas..

Using HFTA

I just ran a pair of 3element antennas for 20m over flat ground
The main lobe for 30ft is about 30 deg
for 60ft it's about 16 deg
for the pair it's at 20 deg.

Changing to 6 elements, it's much the same:
30 - 28 deg
60' - 16 deg
pair - 19 deg

Even going to 50 MHz
The 30ft antenna has lobes at 9.5 and 28.5
The 60ft @ 4.5,14, 25
the pair a big lobe at 5.5, two small lobes at 15.5, 22.5, then another big 
lobe at 33.5


Something is odd though..
The results for the latter are the same regardless of the ground type. 
perhaps it's because of the fairly high gain antennas..


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