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[TowerTalk] Changing interaction of M2 40M4LLDD on 15

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Subject: [TowerTalk] Changing interaction of M2 40M4LLDD on 15
From: "Jim Thomson" <jim.thom@telus.net>
Date: Tue, 16 Feb 2016 21:11:27 -0800
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Date: Mon, 15 Feb 2016 08:56:36 -0500
From: "StellarCAT" <rxdesign@ssvecnet.com>
To: "tower" <towertalk@contesting.com>
Subject: [TowerTalk] Changing interaction of M2 40M4LLDD on 15

Hello to those that have the 40M4LLDD.... I believe I have found a way to 
eliminate the interaction of the 40 to a 15. I?ve done a good bit of modeling 
and came up with a possible solution. I?m happy to pass this along to anyone 
that wants to try it. I?d love to know if it works as modeled. Write to me at 
my QRZ email address for details. 

I hope to build the antenna, test it at 36? (test tower) and then add this to 
see if indeed it does the trick. Note although I (believe) I know what needs to 
be done I don?t yet know how it would be done mechanically ? i.e. the 
specifics. It isn?t really complicated at all, pretty basic change in principle 
so shouldn?t be difficult.

Gary Myers
K9RX

##  so why doesn’t  M2, just build the damned thing right the 1st time ???  
Optibeam uses decoupling stubs on their version of their 4 el  40m yagi.   One 
on each side of boom,
so 8 x stubs in all.   The stubes on the optibeam appear to be small gauge al, 
coming out from the 40m els..at at right angle for a couple of inches, then 
parallel to the ele for a 
couple of feet.  Far end  of stub is held in place with a small insulator back 
to the ele.    You can see the concept on their install manual.   Done right, 
the 40m yagi can be very close to 
a 15m yagi.   These ants have to resonate some where, so the resonance will no 
doubt be shifted higher up in freq. 

## F12s  N series of 40m eles, on their 1-2-3 ele 40m ants.... don’t resonate 
on 15m.  However they will  resonate on aprx 24 mhz...which will screw up a 12m 
yagi.   f12 claims their N series of 40m
arrays can be within  just 3 feet  of another  F12  monobander or  tribander  ( 
20-15-10m).     F12 didn’t use stubs.  They used longer eles, ranging from  
aprx 59 feet for the ref  to 51 feet  for the 
dir.   Longer eles + LL rods. 

##  This  40m yagi and interaction to a 15m yagi  has been an issue for decades 
now.....and is easily resolved.   Dunno why the folks at M2 have not figured it 
out...yet. 

Jim   VE7RF
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