[TowerTalk] Force 12 C3S Experience
Kenneth D. Grimm
Thu, 05 Nov 1998 11:51:19 -0500
This is very discouraging. When I put up my EF-420/240 I only had to
re-drill one of the six elements. I thought it was just a fluke.
Greg Clark wrote:
> Well, it's my turn to let you in on some of my Force 12 C3S experiences.
> I purchased 2 C3S's almost 18 or 19 months ago. They've been in the
> barn until time and money allowed me to do some work with them. The
> idea was to have 2 of them in a stack configuration for my second radio.
> Well, I still don't have alot of time or money, so my goal has been to
> get one of the antennas on a side-mount dedicated to radio #2. I
> started working on the antenna on a Sunday and have been doing part-time
> work on it from that point. It has taken about 3 hours total to
> - No major ones, but I was starting to worry. The first element
> assembled needed to have six rivet holes re-drilled. This number
> decreased for each element thereafter until I got to an element that
> needed no drilling..yea.
> - Tuning...what a pain in the rear..at least for 10m. I've seen similar
> comments from others and I can tell you "I feel your pain".
> My tuning setup consists of about 40ft of RG-213...not the 100ft as
> defined in the manual. I then connect an Autek RF-1 antenna analyzer to
> one end of the 213 and the other is feeding a new W2AU beam balun. To
> tune the antenna off of the tower, I hoist the antenna between my 2
> towers so that it is pointing straight up with the reflector about 6
> feet off of the ground.
> Out of the Box - Per the manual SWR points are as follows:
> 20m (final)
> 1.5 - 14.0
> 1.2 - 14.1
> 1.0 - 14.2
> 1.3 - 14.3
> 2.9 - 21.0
> 2.2 - 21.1
> 1.6 - 21.2
> 1.1 - 21.3
> 1.3 - 21.4
> 7.5 - 28.0
> 6.6 - 28.2
> 5.5 - 28.4
> 4.4 - 28.6
> 3.2 - 28.8
> 1.0 - 29.33 - Kinda high in the band huh?
> Well, per the manual, I was able to lengthen the 15m element and ended
> up with a curve that I was happy with. Here is it's final plot.
> 15m final
> 1.8 - 21.0
> 1.4 - 21.1
> 1.6 - 21.2
> 2.2 - 21.3
> 3.0 - 21.4
> On 10m I was in a pinch. On one of the 10m elements, there were only 3
> rivet holes to extend the element, on the other 10m element there were
> 4. Even when I extended the element tips to their maximum, the resonant
> point on 10 was up at 28.600.
> So, due to me running out of element tip to lengthen, I then went to the
> next section of the element toward the boom to look for some extra
> length. I did this on both 10m elements. This was not a quick and
> simple process. I finally ended up with the following curve for 10m.
> 10m final
> 2.2 - 28.0
> 1.4 - 28.2
> 1.7 - 28.4
> 2.9 - 28.6
> 4.3 - 28.8
> It ain't great but it's better that what I started with.
> >From the time I hoisted the antenna up the first time to the last time
> that I sat it back on the ground was 2 hours 50 minutes. The majority
> of that time was jerking around with the 10m settings and then
> re-engineering it in the field (drill rivets/drill new holes/pop
> rivets...measure..etc). This was not fun. Thank goodness it's not a
> big antenna but it was still a pain and to boot it was about 30 deg F
> all the time.
> I have another one of these to put up...probably next Summer, but at
> least I will have my notes to get me through that assembly and tuning
> I don't have the antenna on the tower yet. I hope to have it in place
> for SS this weekend. I'll let you know how it performs, but I did want
> those that have the C3S and have had problems on 10m to know that there
> is a way to make it work. I, like other TT posters wonder why the
> antenna was designed for such a high 10m resonant frequency of 28.800.
> Why not ship it with about 4 more inches of length in the 10m elements
> to save the majority of the users the above described procedure?
> Hope this helps someone out there.
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