I recently, with much trepidation, decided to take down my 6 element KLM
15 and 10 antennas. I have been on these two bands exclusively for several
years
and decided to get back on 20 and 40. After considering the size of my
tower and the suggestions of several friends, I decide to try the Force
12 antennas. There is suprisingly little detailed information about the
C-3 in comparison to the current popular antennas (TH7 and KT34XA). I
suppose that the reason is that the 18 foot boom on the C-3 is so much
shorter that it can't be in the same class. My hope was that the C-3 was
not "too much" down from the KT34X. I also purchased the EF-240X
(2 element 40 on a 20 foot boom).
I was pleased to find that the advertising about the ease of construction
is not hype. The 2 element 40 still took me a while to put together...
the C-3 went together in about 3 hours from beginning to end. (Thats 7
elements). I didnt have to get up once to put the elements together. I
sure like the rivets for putting the elements together. I wasnt very
happy with the instructions ( too much detail on simple things and other
things left completely out) Fortunately, you really don't need
instructions. If you really don't understand, use the 1-800 number and
call Tom. He always seems to be there and is very helpful.
The antennas are mounted on a 90 foot tower, the forty is at 90 feet with
the C-3 at appx 100 feet.
The SWR curves for the C-3 )taken with an MFJ SWR Analyzer) are
20 Meters
14.00 1.5
14.05 1.4
14.10 1.4
14.15 1.3
14.20 1.3
14.25 1.4
14.30 1.4
14.35 1.4
14.40 1.5
2:1 Points are 13.68 - 15.51
15 Meters (Low Setting)
21.00 1.8
21.05 1.7
21.10 1.6
21.15 1.6
21.20 1.6
21.25 1.7
21.30 1.8
21.35 2.0
21.40 2.2
2:1 Points are 20.93 - 21.360
10 Meter (Low Setting)
28.0 1.6
28.1 1.6
28.2 1.6
28.3 1.5
28.4 1.5
28.5 1.5
28.6 1.6
28.7 1.6
28.8 1.6
28.9 1.7
29.0 1.7
2:1 Points below 27.0 - 29.200
I believe that the 2 element 40 is causing interaction with the C-3 on
15. The SWR curve seems to be different than I would have expected. The
swr is measured at the end of 125" piece of RG 213 as suggested by the
instructions.
How does it work? It seems to work pretty well.
How does it compare with a KT34XA? I have done some comparisons with NA5C
who has a KT34XA that is about 100' and we know works well. The following
tests were conducted on 20 meters ssb.
W7 Signals were dead even
W4 Signals were identical
K Signals identical
F KT34XA 1-2 S Units better
J8 C-3 20 db better
8P C-3 10 db better
PY C-3 10 db better
9Y even
K6 even
I'm not sure what this means. The antennas were the same 5/9 times, the
KT34XA was better 1/9 time and the C-3 was better 3/9. We have not done
comparisons on 15 or 10 yet. Tom predicted that the KT34XA would probably
be comparatively better on 15 and even more so on 10. It is very hard to do
comparisons on 10 with such poor conditions.
When I can do some comparative testing on 10/15 I'll post the results.
Incidentally, I do believe that the I notice less noise with the C-3 than
my old 6 element KLM. I hope that this information is helpful. If anyone
is interested in my observations of the 2 element 40, I'll be glad to
post them.
Bill Parry
W5VX
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