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Topband: too flat VSWR problem?

To: topband@contesting.com
Subject: Topband: too flat VSWR problem?
From: "Alan D. Snyder KF3B" <kf3b@yardley.com>
Date: Mon, 17 Nov 2008 14:29:51 -0500
List-post: <topband@contesting.com">mailto:topband@contesting.com>
Hi All

Just finished reworking the radial frame and feedpoint connection for my 
1/4 wl elevated radial vertical.
The VSWR profile doesn't seem right to me.  It feels too flat and 
probably is indicative of something wrong. 

Am hoping for wisdom from the group.

The vertical is built from Rohn 25 with a top "stinger".  At 25 feet 
three Rohn insulators separate 13 additional sections plus stinger.  
Stinger's length set for resonance at 1.820.  There are 24 elevated 
radials with sort of irregular spacing, each tied to the angle iron 
frame which stands off via insulators.  The vertical is fed at the 25 
foot level just above the insulators through a 1:1 current balun with 
RG-213/U.  I walked each radial with a current probe and cut each at the 
zero current point at 1.820.  After cutting each radial to length, I did 
not take another walk around to see if anything changed.

The VSWR profile is:
1.800  1.0 : 1
1.825  1,0
1.850  1.0
1.875  1.0
1.900  1.1
1.925  1.3
1.950  1.4
...

Looking forward to your constructive comments and thanking you all in 
advance.

73, Alan KF3B



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