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

[Jim Lux <jimlux@earthlink.net>]

At 05:18 PM 7/12/2004 -0700, Jim Lux wrote:
> 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
> > >
> > >
>
> 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..

Mis-read Chuck's original statement.. However, running the simulation with 
an antenna at 45 feet,
 at 14.2 MHz, 3 element, 45' lobe at 21.5deg
Likewise, changing to 50MHz, the main lobe is at 6.25 deg...
And, of course, the sidelobes (which are a LOT bigger with the single 
antenna)are not where the sidelobes of the pair are.  

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