Dave's model was for the 2el 40m coil loaded OptiBeam and I concur with his
post. The 40M4LLDD is a different animal, its 15m resonance was previously
posted by N2IC.
http://lists.contesting.com/archives//html/Towertalk/2015-09/msg00315.html
John KK9A
To: "tower" <towertalk@contesting.com>
Subject: Re: [TowerTalk] 40m optibeam de-coupling stubs
From: "StellarCAT" <rxdesign@ssvecnet.com>
Date: Mon, 16 Nov 2015 21:06:50 -0500
Dave.... please send me that file if you don't mind (and if it is ok with
Optibeam).
I asked Richard, N5ZC to test his 40M4LLDD recently .... I asked him to
check
to see what the SWR was on 15 (and 20) meters. I have plans on having
stacked
6/6 on 15 with the top antenna 30' from this 40 meter beam...
he got back to me ... the 20 seems fine ... but on the 15 check: sure enough
-
1.3:1 at 21.2! OUCH! That concerns me a bit.
I modeled it - but I didn't want any issues related to modeling the linear
loaded 40 and instead modeled a 2 element full size... with that resonating
properly on 40 I tested it on 15 and found it was not resonate on 15 but
rather
higher up - maybe around 22 Mhz. And likewise had no effect on
SWR/FB/gain....
I'm not sure if this is the case and the LLDD because of its altered design
is
indeed resonate lower .... or what.
I know a good deal use the antenna, the 4LLDD, alone - I can't afford to
have
yet another tower just for it...
Gary
K9RX
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