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Force 12 C-3 and C-4 SWR curves

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Subject: Force 12 C-3 and C-4 SWR curves
From: (Pete Smith)
Date: Wed, 1 Jan 1997 12:32:49 -0800
Can any fellow C-3 or C-4 owners share SWR curves with me?

I'm trying to understand what happened when I installed the C-4C conversion
kit on my C-3.  All the SWR curves on the other bands shifted.  I talked
with Tom, N6BT, about it and he was concerned but we could not figure out
what might have happened.  I can't discern any change in performance but the
SWR changes tell me something happened.

All the info I really need is:

2:1 points (or SWR at band-edge if it's not 2:1 when you pass out of the
band), lowest SWR and frequency of lowest SWR on each relevant band (omit 18
and 24 mHz).

Mine are as follows:

Band                C-3                                  C-4                   

20m. 1.9 at 14,000, 1.45 at 14.350,     1.4 at 14000, 1.35 at 14350
     minimum 1.1 at 14200               minimum 1.15 at 14100

15m. 1.75 at 21000, 2.0 at  21450,      2.05 at 21000, 1.45 at 21450
     minimum 1.25 at 21200              minimum 1.5 at 21200
10m. 1.5 at 28000, 2.0 at 29600,        1.25 at 28000, 2.4 at 29700
     minima 1.4 at 28150 and 1.15       minima 1.1 at 28100 and 1.3 at
     at 29300                           29500

40m.                                    1.25 at 7000, 2.0 at 7175, 
                                        minimum 1.2 at 7030 

Of course, the 40-meter curve and resonant frequency is very dependent on
the adjustment of the loading wires and the hairpin matching coil.  My
ten-meter driven element uses the inital, standard set of rivet holes.

Any bright ideas on possible assembly errors appreciated, because I'm going
up there Saturday.  About the only thing I can think of is the position of
the 40-meter element on the boom.  Carefully measured according to the
manual, but I could've goofed.  On mine, the crossbar for the loading wires
on the 40-meter actually overlaps the 15-meter reflector by an inch or so,
and the other end of it comes within about 3 inches of my mast above the boom.

Please reply direct, for the sake of bandwidth.  Thanks!

73, Pete Smith N4ZR 
West (bigawd) Virginia

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