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[TowerTalk] XM240 interaction - question

To: <towertalk@contesting.com>
Subject: [TowerTalk] XM240 interaction - question
From: k6ll@juno.com (k6ll@juno.com)
Date: Sun, 18 Oct 1998 03:33:53 +0100

On Sat, 17 Oct 1998 19:29:00 -0700 Brian.Harris@sv.sc.philips.com (Brian
Harris) writes:
>
>Sam (et al),
>
>When it was by itself my XM240 I measured the forward and reflected 
>power using 
>two different Drake W-4 wattmeters.  The SWR in the first two columns 
>below was 
>caculated by the formula (Pf+Pr/Pf-Pr). 



Whoops, the formula should be:

SWR = (1+SQRT(REFLECTED/FORWARD))/(1-SQRT(REFLECTED/FORWARD))




 The third column was obtained 
>by using 
>a Mirage SWR meter in the shack.  The Drake measurements were at the 
>end of 85' 
>of new coax but similar readings were measured in the shack through 
>another 
>100' or so of coax.  While I don't believe the actual readings from 
>the Drake 
>meters, their relative readings seem to show there is little effect on 
>my XM240 
>by the TH6.  The TH6 boom is parallel to the XM240 boom and the TH6 is 
>10' 
>below the XM240.  I split the CW and LOW measurements on the XM240.    
>
>
>On the other hand, when installed under the XM240, the TH6's minimum 
>SWR point 
>on 15 meters (I haven't measured resonance yet) moved downward about 
>200 KHz 
>from where it was when the TH6 was pointed straight up with the 
>reflector about 
>20' above the ground.  The behavior on 20 and 10 meters was not 
>noticeably 
>effected.  The TH6 was tuned for LO PHONE.
>
>Freq    SWR (solo)     SWR (w/TH6)     SWR (w/TH6 and Mirage SWR 
>meter) 
>
>7.0     1.17           1.12            1.3  
>7.1     1.00           1.04            1.1 
>7.2     1.06           1.04            1.2 
>7.3     1.30           1.17            1.6


Ok, the first two columns were calculated incorrectly, but the
Mirage column looks suspiciously flat also. I've never seen
a CC 40-2 this broad. I think something is amiss with the meter,
or the coax is bad, or the reflector has fallen off, or
something.

Dave Hachadorian, K6LL
Yuma, AZ
K6LL@juno.com



















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