[TowerTalk] Force 12 C3E Installed

[Dick Green]

As I mentioned in a previous post, in an effort to quickly add a second
tower and tribander to my single-op two-radio contest station for the
upcoming season, I recently completed
installation of a 48' AB-577/GRC military surplus portable mast with a Force
12 C3E and an Alliance HD-73 rotor.

It will be a while before I have enough experience with the antenna to
report in detail on the C3E, but my initial impressions are very favorable:

- Construction was a breeze -- a fraction of the time it took to assemble my
TH-7.

- Love those rivets! What a great way to put elements together.

- Love the fixed boom-to-element mounts.

- Some care is needed tightening U-bolts to avoid misaligning element tips,
especially in the driver area.

- Excellent boom-to-mast clamp design.

- SWR curves are to factory spec, under 2:1 on 20M and 15M, under 2:1 in the
lower 1MHz of 10M, and generally under 1.5:1 where I want to operate. For
now, I've left the adjustable elements in the default position, which is a
good compromise but favors phone somewhat. I may adjust the 15M and 10M
curves to optimize for CW, but not until I run a few contests (the LK550-ZC
amp I'll be using with this beam doesn't care much about SWR under 3:1.)

- I have a TH-7 on a U.S. Tower MA770MDP about 200 feet away from the C3E.
The towers are at the same elevation on the property. The TH-7 feedline is
260 feet of LMR400UF and 80 feet of RG-213. The C3E feedline is 200 feet of
LMR400DB and 70 feet of 9913F. In receive-only DX tests with both beams at
48', the forward gain is virtually identical. The C3E sometimes appears to
be maybe 1/2 S-unit better on 20M and the TH-7 sometimes appears to be maybe
1/2 S-unit better on 10M. Note that the C3E has a slightly better feedline
situation, which might be affecting results on 10M. Of course, these tests
are highly unscientific because QSB and switching transients make it
impossible to quantify small differences. But I know what I can hear. I'm
setting up some more rigorous tests with a friend who lives about 1 mile
away to see if I can quantify the subtle differences. Also, it'll be a while
before I can get a handle on differences in gain at different arrival
angles. So far, the differences are too small to detect, even with the TH-7
at 70' and the C3E at 48'.

- There is no comparison in F/B: the TH-7 simply blows the C3E away. If I
point both beams at a European station in QSO with a west coast station, I
can barely hear hear the west coast station on the TH-7, but can hear it
quite well on the C3E. This is exactly what I expected from the published
specs for both antennas, and what I wanted for the beam antenna on my
multiplier radio. Also, the C3E can be instantly switched to the run radio
to better work stations off the back of the beam. I figured the sacrifice in
F/B was worth the extra flexibility.

- On a completely anecdotal basis, I'm really blown away by how good the C3E
forward gain is compared to the TH-7. The results are pretty much what was
reported in the N0AX/K7LXC tribander tests, which I didn't believe when I
first saw them. Since the antennas can be tested at the same height and
elevation, I'm looking forward to doing some more rigorous tests and
comparing performance under contest conditions. I'll report my results.

For now, I'd highly recommend the C3E if you can live with the F/B.

73, Dick WC1M



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