After messing around for two nights I finally have my 160m shunt retuned.
This summer I replaced my Tennadyne T10 + 40m dipole with a smaller Force 12 C4S beam.
The new beam is about about 50% of the size as my previous top hat. Needless to say
that my 160m shunt loaded tower was no longer was tuned to the point where my
radio would put very much RF into the antenna.
After a couple of (slightly) missed attempts on Friday and Saturday night to retune
it I went outside today in my snow pants, jacket, and boots to re-measure the
antenna. R225 and X285. After plugging it into a LC spreadsheet provided
by N0FP. It turns out that I would need about 300pF to get the antenna to match.
I went to St Cloud this afternoon and bought a new electrical box and misc parts for
other projects this afternoon. Upon returning home I disassembled my old matching
circuit and salvaged the parts. After some messing around I found that a combination
of a 150pF doorknob capacitor and a 75-150pF variable capacitor that would give me
the appropriate amount of tuning latitude for a match.
It was very cold and dark when I went outside to test it and tune it up tonight. I
have a 1.6:1 match with R35 and X12. I probably could have tuned it up a little tighter
but my family was waiting to eat dinner while I was playing outside with the tower.
I learned a lot this weekend. Ford Peterson N0FP shared a ton of knowledge with me.
I will try to take some better pictures when time permits. The schematic should give
you a general understanding of how it works. About 300pF in series is what it takes
to tune it up. The toroid that you see in the picture is a balun that is not included
in the schematic. The radio seems to be pretty happy and I am hearing plenty of signals
on top band!
73 de NG0R