[TowerTalk] Changing interaction of M2 40M4LLDD on 15

[Jim Thomson]

Date: Mon, 15 Feb 2016 08:56:36 -0500
From: "StellarCAT" <rxdesign at ssvecnet.com>
To: "tower" <towertalk at 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