Jim, W0EEA first email was correct. You can't increase gain and not
decrease beamwidth somehow. Stacking the antennas vertically reduces the
vertical beamwidth. The horizontal is mostly unaffected. Stacking the
beams horizontally reduces the horizontal beamwidth. The vertical is mostly
unaffected. Since for terrestrial communications you are not usually
concerned about narrowing the vertical beamwidth most guys stack them
vertically. As far as the optimum stacking distance is concerned it is a
function of frequency, antenna gain, boom length, etc. I have seen lots of
"rules of thumb" used. Some made some sense others seemed like BS. In my
case I have always checked with the antenna manufacturer. The good ones can
usually tell you what the optimum stacking distance should be. If that info
isn't available manufacturer unknown, out of business or homebrew) then I
would use a software simulation like EZNEC. You can usually find a stacking
distance that will give you something close to the maximum theoretical
increase in gain (3 dB) while keeping the front to back and side lobe levels
reasonable.
73
Jim, W4KXY
-----Original Message-----
From: vhfcontesting-bounces@contesting.com
[mailto:vhfcontesting-bounces@contesting.com] On Behalf Of Joe Serocki
Sent: Saturday, November 29, 2008 9:01 PM
To: w0eea@sbbco.net; vhfcontesting@contesting.com; nlrs@mailman.qth.net
Subject: Re: [VHFcontesting] HELP! Looking for stacking info on 1.2GHZ yagis
I never thought of stacking side by side, I think that would accomplish more
on the horizontal plane. Since you are already pointed pretty flat, you
really want to add beam width and gain at the same time, I think this is
what this will accomplish, no?
If you stack vertically, don't you just get added beam width on the vertical
plane, something that's kind of useless?
Joe Serocki
-----Original Message-----
From: w0eea@sbbco.net [mailto:w0eea@sbbco.net]
Sent: Saturday, November 29, 2008 7:25 PM
To: Joe Serocki; vhfcontesting@contesting.com; nlrs@mailman.qth.net
Subject: Re: [VHFcontesting] HELP! Looking for stacking info on 1.2GHZ yagis
Subject: [VHFcontesting] HELP! Looking for stacking info on 1.2GHZ yagis
> I have two and a splitter and phasing harness, 22 element beams, but how
> far apart? Looking for recommendations. I want to increase gain but not
> reduce beam width.
> Thanks
> Joe Serocki, N9IFG
>
Joe the increase in gain comes from narrowing the beam width.
If you stack them vertically the vertical beam width is narrowed. Stack
them side by side
to narrow the horizontal beam width. Vertical stacking distance is 26".
Horizontal 28".
I have seen recommendations for slightly smaller stacking distances of 24"
and 26" but
I believe the wider spacing is better. M2 shows even tighter spacing for
their current
22 el yagis but their splitter is based on out of phase mounting of the
antennas so it
wouldn't apply here.
73, Jim W0EEA
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