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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