(NOTE:  Also see "Stacking 40-2CD and Tribander #1 also on this web page)

Compiled off the CQ-CONTEST reflector by KA9FOX

THE ORIGINAL QUESTION:

From: g3ozf
To: CQ-CONTEST
Subject: 40-2CD stacking
Date: Friday, March 10, 1995 8:26PM

Can anyone help me with reasonable stacking distances ? I want to put a
Cushcraft 40-2CD above my TH6DXX. What's the minimum I can get away with -
and should the booms be aligned, or at 90 degrees to each other ?

Don - G3OZF (g3ozf@mayerin.demon.co.uk)
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THE REPLIES:
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Subj:  FW: 40-2CD stacking
Date:  Fri, Mar 10, 1995 9:15 PM CDT
From:  TSkelton@engineer.ClemsonSC.ATTGIS.COM
To: CQ-CONTEST@tgv.com (CQ Contest)

I asked a similar question last year, and as I remember the concensus was
that if neither antenna used all insulated elements (as KLM, etc.) they did
not have to be at 90 degrees.  The rule of thumb for distance from the ARRL
handbook (I believe) is 1/2 the distance of the shortest boom.   So Don, in
your case, the booms are 23 ft for 40-2 CD and 24 ft (I think) for TH6 I'd
go with at least 12 feet.  The problem will probably be the interaction 
between the 15m TH6 sections and 40-2 CD at less separation.  I have a 40-2CD
spaced 10 feet from a Hygain 3 element 20m monobander and can't see
any interaction.  A friend of mine had tremendous interaction with a 40-2CD
and a KLM KT34XA separated by 12 feet until he turned the 40-2CD 90
degrees to the KLM.

73,Tom WB4iUX    Tom.Skelton@ClemsonSC.ATTGIS.COM

PS:  Don't ever try to stack a WARC antenna for 17m near a 40-2CD;
the interaction is fierce.  The geometry of the 40-2CD actually makes it
a pretty good 17m antenna!
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Subj:  Re: 40-2CD stacking
Date:  Sat, Mar 11, 1995 12:27 AM CDT
From:  k1vr@k1vr.jjm.com

I have NO scientific basis for the following.

I have a 40-2CD on a RINGROTOR at 90', and a TH6 at 97.5'.  Thus, I can 
independently rotate each.  Rotating the one has no effect on the other.
Each was fed, at the time of the test, with hardline, but RG-213 jumpers 
the last few feet.

I keep thinking I should increase the distance between the beams from 7.5
to 11 feet (about .25 wave on 15?), but then I decide that more radials
on 160 is more important.
 
Fred Hopengarten K1VR
k1vr@k1vr.jjm.com
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Subj:  FW: 40-2CD stacking
Date:  Sun, Mar 12, 1995 9:58 AM CDT
From:  joe.ham@ctobbs.com

I stacked a 2 element Cushcraft 40 meter beam above a TH7DXX back in
1986.  There were 9 feet of separation between the two booms, which
were parallel rather than perpendicular to each other. Both antennaes
were above a salt water ground.  I had NO interaction at all between the
two.  At times worked contests multi single with one station on the TH7
and another on the 40 at the same time.  This was before the current
bandpass filters---still no problem.

I recommend you try at least 8 feet of separation, and if you can get
more all the better.  You'll find that amount of separation above a good
ground will work great.

73
Jerry
KG6LF