Hi, Ed!
I bought a small wire clamp from Lowe's the other day, a Southwire Lay-In Lug,
Model LUG4-14C (UPC 0-32886-79135-2), and am using that to clamp the wire
from the top of the matching transformer onto the coil. The coil wire is #14 THHN and
the insulation is scraped at the desired tap point. The other end of
that wire has a ring terminal. The matching transformer is mounted inside a 4x4 inch
NEMA box, with two 1/4 inch holes fitted with brass hardware, for the hot side and
for ground, and there are brass washers and wing nuts on the outside of the NEMA
box to facilitate disassembly. There is, of course an SO-239 coax socket, as well.
The taps protrude from the bottom, through small drilled holes, and they're made from
#20 enamelled wire and fitted with quick-disconnect terminals. The hot (antenna) side
of the coil is also fitted with a 1/4 inch ring terminal, as is the lead from the bottom of
the vertical cage, and they're fastened with a 1/4 inch brass bolt. The ground side
of the matching transformer is connected to the ground system triangle with some 1/2
inch braid, and a separate braid runs from the bottom of the coil to the ground system, too.
The matching transformer has a rain bonnet carved from a large empty plastic coffee tub.
When I set this up last week, I was able to find my 630m and 2200m tap points fairly
easily, and have marked them, as well as the correct taps on the matching transformer.
For each session, or at least every time I change bands, those marked points are, of
course, just starting points. However, the weather has been fairly consistent the last 2
weeks, so it's been a fairly easy job, particularly with the AA-54.
Once I'm satisfied with the match at the coax port on the matching transformer, I connect
my coax (about 75 feet of RG14A/U), and retreat to the basement shack, where I re-measure
at the point where the coax feedthrough protrudes from the wall, and again at the
operating position. So far, my SWR curves have been consistent between these 3 measurements.
And, yes, the curve did shift downward in frequency by about a kHz this morning, thanks to
some overnight rain. Due to the cage vertical leg, my SWR curve is fairly flat, at least
compared to what I deal with in Florida, and the SWR for the WSPR segment is still under 1.3:1.
Like you, I'm driving my amp (WB4JWM non-linear dual IRF250) with the 1-1.5 mW output
from the K3's transverter port. I'm powering the amp with a MeanWell 350-24 power supply that
is adjustable from about 21 to 27V.
I haven't played with SDR-IQ at all, but I'll look into it after I work through my other projects.
I also have a Monitor Sensors 2200m transverter that I'll try to connect in, perhaps this weekend.
Having lived in NH for a couple of dozen years, I'm well aware of your climate challenges, but
this QTH is a summer retreat during hurricane season, and we generally return to Florida before
first frost in early November. (Altitude is about 2200 ft ASL).
I hadn't been on 630m for a couple of years, so I'm still scraping a lot of mental barnacles...
Thanks and very 73,
Brandy