[TowerTalk] Help with Force 12 C3S 10-Meter Adjustments

[Bill Parry]

Bob,

I have had two of the C3Es over the last 20 years.  I found that using the measurements in the instructions worked out just fine with the exception of 15 because I have it stacked with a 40 meter beam and they interacted until I turned them at 90 degrees from each other.  Excellent antenna and easy to put together.

Bill W5VX

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Bob K6UJ
Sent: Sunday, November 12, 2017 9:09 PM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Help with Force 12 C3S 10-Meter Adjustments

Hi Jim,
What I did was note the resonant frequency at 70 feet before finishing securing to the mast then lowering it down and sat it on saw horses.  Took note of the new resonant freq on the saw horses and adjusted the tips to increase the resonant freq on the saw horses the same amount that was needed at 70 feet.  It turned out to be right where I wanted it down on the CW end when I raised it up to 70 feet. 
I was thinking if this did not work out I would hoist it up to about 15 feet on some of the fiberglass military poles I have that you described  and adjust there but I was lucky and this worked fine.

BobK6UJ

      From: Jim Brown <jim at audiosystemsgroup.com>
 To: towertalk at contesting.com
 Sent: Sunday, November 12, 2017 2:23 PM
 Subject: Re: [TowerTalk] Help with Force 12 C3S 10-Meter Adjustments
   
On 11/12/2017 1:49 PM, Bob K6UJ wrote:
> What I did was make sure
> the driver tube was well lubed with Penetrox and slid it out in 1/2 " 
> increments tillit got down where it was good down in the CW end of the 
> band

Of course. But the tricky part is being able to rig the antenna so that SWR can be measured at sufficient height to remove ground influence on the tuning AND the so that it can easily lower it for adjustments. Or access the adjustments from a tall A-frame ladder while it's in the air. 
While adjusting a very different 4-el for 10M, I found that the frequency of lowest SWR went DOWN as I raised the antenna, contrary to what usually happens with a simpler antenna like a dipole.

A rigging method we often use for portable operations like CQP, 7QP, and FD uses the 4-ft 2-in o.d. surplus military mast sections in combination with a tripod base fitting. If the "legs" are two elements tall, additional mast sections can be pushed up through the center of the tripod fitting. We use this to get a C3SS up 20-25 ft. We first learned of this method from a talk that K7JA did at Visalia several years ago.

73, Jim K9YC

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