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Fwd: [Towertalk] Force12 C4-SXL

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Subject: Fwd: [Towertalk] Force12 C4-SXL
From: (Gene S.)
Date: Sun, 18 Aug 2002 14:37:50 -0600
I installed a C4-XL a few weeks ago, same basic design as your C4-SXL.

Tuning the 40 meter elements is an interesting affair.

With advice from Natan and Pete Smith  N4ZR, I got the linear loading 
assemblies constructed and put the antenna in the air.   The assembly 
manual needs a lot of help in the 40 meter section, to be blunt, it 
stinks.  The C-3 manual is excellent.

Make sure you have the linear loading wires in the correct 
configuration,  the manual refers to  as "staggered".  Initially,  I didn't 
see what they meant by "staggered" and did it wrong.

At my location I found the 40 meter portion of the antenna to be "very" 
sensitive to the ground. Trying to tune it at 10 - 12 feet above the ground 
was a waste of time.

You didn't say if you found a dip in the SWR near any band segment on 
40.  I found the specs given in the manual are approximations.  Setting 
them to the 7190 suggested point  gave me a dip at 7.000 Mhz.   Trying to 
find the dip at 12 feet above the ground never resulted in anything better 
than 3.0 to 1 that you're seeing, it had to go up higher.

Natan suggested that I set the reflector and driver to the measurements in 
the manual (as a starting point) and further adjust the driver only. I did 
change the suggested reflector setting slightly,  but made all subsequent 
adjustments on the driver.

At 25 feet the SWR was 2.0 to 1 at 7190.   Raising the antenna to 75 feet 
dropped the SWR to 1.5 to 1.

Finding the dip was important because it indicated the antenna did load, 
but it was being affected by the ground. I made a few adjustments of the 
tuning jumpers and the hairpin and got the SWR to  1.5 to 1 at 7190 when 
the antenna is at 75 feet, it does stay low across the suggested 130KC 
range.  The hairpin is spread about 3/4" between the turns.

SWR on the other bands is virtually flat,   the front to back is 
excellent.   The performance on 10 - 15 - 20 is noticeably better than my 
25 year old KT-34.

It does work, but the manual is weak when addressing the linear loading 
wires and their assembly.  A couple of "good" pictures would have saved me 
many hours of hunting an pecking..


Gene K5GS

>I am having hard time to lower  SWR on 40 mtr band on C4-SXL.  I have
>just finished the assembly and found this problem.  all ok on 10 - 20
>meter band SWR.
>I used RF choke ( 10 inch dia.) and connected hair-pin coil...SWR shows
>I removed hair-pin coil....SWR shows 3.
>I did spreading or pushing the coil, but it didn't change at all.
>I rechecked LL assembly, but I couldn't find anything .
>I must have made some thing wrong, but I couldn't figure out.
>de  VE3JOY, Isao Endo

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