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[TowerTalk] XM240 interaction - question

To: <towertalk@contesting.com>
Subject: [TowerTalk] XM240 interaction - question
From: k3nd@yahoo.com (GALE STEWARD)
Date: Mon, 19 Oct 1998 07:34:07 -0700 (PDT)






---Sam Ferris  wrote:
>
> 
> Wonder if any CC 402cd or XM240 owners can give me some advice
regarding 
> interaction associated with a XM240 and a TH7 stacked about 6 feet
apart 
> (that's all the space I reasonably have).  Here's the situation.
> 
> Put up my new XM240 a couple of days ago - 5.25 hours on the tower 
> removing the old Hygain 402 BA and pulling and assembling the XM240
up 
> through a couple of other antennas.  The TH7 is mounted at 70 feet
just 
> above the top of the tower and the XM240 is about 6 feet above that.
 The 
> booms are perpendicular to each other since that is the way that I
had 
> the hygain 402 mounted previously to reduce SWR impacts on 15 metres
on 
> the TH7.  Presently the SWR on the XM240 is a little high, bottoming 
> out at about 1.55 at 7.050 , 1.8 at 7.000 and 2.0 at 7.125.  I set
it for 
> the CW setting in the manual and followed the advice regarding the 
> measurement mistakes in the manual posted by others - most helpful. 
In 
> comparison to the Hygain 402, it seems that impacts on the TH7 are
about 
> the same, the 15 metre SWR curve looks about the same as before and
the 
> SWR on 10 and 20 metres is now actually lower than with the previous
40 
> metre antenna.
> 
> My question is if any others have similar setups with PARALLEL
BOOMS, and 
> if such a change to my system would reduce the impact on the XM240 by 
> lowering the SWR.  Bottom line is I am not all that anxious to make
many 
> more trips up the tower to spin it.
> 
Sam,
I have had a similiar setup for quite a few years.  I have a TH6DXX @
62ft and a 40-2CD @ 72 ft.  The TH6 is setup with the CW dimensions
and was up some years before I added the 40-2CD.  Both boom are
"in-line".  After installation of the 40, I noticed that the VSWR of
the TH6 on 15M went up, from like 1.2:1 to 1.5:1 at 21025.  It seems
like the F/B on 15 degraded slightly also.  The pattern is still good
and the gain seems up there as it will bust pileups in a DX contest
with all the big guns. the 40m VSWR (antenna set for CW) is almost
exactly per the CC specs.  I think the 40 will affect the 15, not the
other way around.  Yours spacing is a little tighter than mine so the
effects may be more pronounced.  Also, a TH6 may be more/less effected
than a TH7.  GL with ur project.

73, Stew, K3ND
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