Since I'm done with 40 meter DXCC converting the Create vertical to 160 was
probably the best idea I've had in a long time. I got out the Create manual,
which I apparently never read and found an interesting little paragraph
regarding impedance matching.
The Create was basically a full size 40 meter vertical and the manual says to
expect a SWR of 2:1.
However, it states the match could be improved with two capacitors to 1.2:1.
The values they gave are 300p to ground and 1500p to the antenna with the 50
ohm coax to the common between the two capacitors.
The 160 ground mounted L came down and a 40m wire replaced it that is about 32'
long. I can match it with my Nye Tuner but I figured I'd try the matching
network. In my junk box I had two 880p 20kv laser caps so I put them on
parallel and a BC band variable to ground for a test. I got a perfect 1:1 match
by adjusting the variable. It measured 225 p so I replaced it with a large mica
cap about 3/4" square from my junk box with no voltage rating. For the acid
test Mr. Alpha 78 now set for PPT operation since the QSK relay is dead, was
brought into play. This is the three tube version and at full output nothing
blew up. This amp melted the solder in a PL-259 once, so I feel OK with the
caps.
The SWR on the 160 antenna is about 1.3:1 with the loading coil I have and
resonant at 2.45 mHz without the coil. My 160 L had an SWR of about 1.7:1 and I
just used the tuner on it.
It appears that for these low to high matches on 160 meters converting the 40
meter reactances, a good starting point would be 6000p to the antenna and 1200p
to ground. I will be trying it on my new antenna and for the 80 meter L I'll be
putting up next to the 40.
This web site has super capacitor, inductor, resonance calculators:
http://www.dressler.com/more_about_rf/rf_formuler.html
Rick Darwicki -= N6PE =-
=================================================
17775 Elmhurst Circle
Yorba Linda, CA 92886
http://www.qsl.net/n6pe/
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