Hullo folks. FWIW.....
I mounted the FCP on my "inverted J" which is about 60 up, 40 over, and
another 40 to 50 over again. About 150 feet of wire on the radiator.
The FCP and transformer box are mounted about 7 feet up. Sent photos to
W0UCE since I still have the step ladder conveniently located.
With 880pf of capacitance in series it is resonant right about 1830. The
autotuner in my ft-920 can tune it easily down at 1800, and runs into
trouble at 1860 up. Have not yet given the K2 tuner a look at the load.
Using the Elecraft K2 S-meter as a field strength meter, sense antenna a
dummy load on a 7 foot jumper, full attenuation/no preamp, the OLD
antenna set up registered S5 on the K2 with 100w going into the antenna
from the FT-920 at its 1:1 SWR point. [K2 in the shack about 75 feet
from base of antenna and old antenna radials described below]
After removing the elevated radials(they were in the way) and installing
the FCP system, yesterday I found that:
20w into the antenna from FT-920 now registers S5 on K2
40w into the antenna from FT-920 now registers S5 plus one bar on K2
60w into the antenna from FT-920 now registers S5 plus two bars K2
100w into the antenna from FT-920 now registers S9 (S5 plus three bars)
I'm pretty sure my K2's S-meter is not well calibrated so there is not a
real quantitative measure there. But the new antenna is a lot better
than the system it replaced. (Note: The K2 bar graph has three bars
between s5 and s9.....> 5||9)
There are still improvements I can make. There is a large coax
choke/balun wound with rg-58 that I'll be replacing with a much shorter
rg-8 jumper.
The original crummy antenna(before FCP installed):
The old radials consisted of 8 radials about 6 feet above ground, all of
35+/- feet in length. There were an additional 20 radials of various
lengths from 16 to 30 feet long. All were tied together at the bottom
of a coil, and the feedline ground tapped the coil where it provided the
best match. The radiator was the same ~150 feet of wire with the same
880pf of capacitance in series. (A mix of 150pf and 82pf panasonic 3kv
ceramics in parallel). The 82pf caps will be switched out to move the
match should the relays prove capable of the task.
The old set up allowed me to run US stations during ARRL 160m in 2010,
but never worked much dx or west coast with 100w.
I wanted to get it all installed before ARRL 160m this year, but that
didn't happen. But maybe my 100w will be less like QRP for Stew Perry.
For my own part, the 30 elevated radials were a maintenance nightmare,
although they were producing better results than 8 uniform length
radials. But every falling tree limb snagged one of them. The FCP
lowers the odds of being hit by a factor of 15. That should cut down on
radial repairs. Cha-Ching :)
Other random thoughts......
My installation of the FCP would have been easy to tune by trial and
error. With the antenna long, a large value air variable could be used.
Tune it to the sweet spot, measure the value of the air variable, and
replace it with the fixed value. I expect my own spark gap to be between
the vertical and the capacitors.
Thanks very much to K2AV for his help with the project. Test drive
for Stew Perry.
73 de w4kaz
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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