David:
You are mistaking "Professional Circles" with a hobby device (NanoVNA), where my stated
usage was testing filter equipment below 50Mhz that comes with SO-239 connectors.
YES, there are some people that actually wish to test and align something
BELOW microwave frequencies. You did not offer an answer to the question;
How would you calibrate and hook up to a 14 Mhz bandpass filter that comes with
SO-239 connectors, to test and align it, using the NanoVNA? If you use a cal standard
set that is not the PL-259 / SO-239, then your reference plane will be meaningless at the actual
input to the filter. But the question becomes, at that low a frequency, does it matter?
Or should I still build a nice crappy SO-239 SOLT cal standard set for the crappy
connector choice that the entire industry puts on ALL amateur HF radios, tuners, amplifiers,
meters, and misc switching equipment and antenna's [because at that freq. it probably does
not matter] ? :-)
Please don't confuse "Professional" with frequency of use. Some frequencies
have plenty of commerical equipment in 2020 shipping with SO-239, and some
with BNC, and some with SMA, and some with Type N.
You can't really tell me that at 14Mhz you will see ANY visible appreciable difference
in signal on the screen between a PL-259, BNC, or Type N or SMA. At that
frequency, inside the chassis, some vendors do not even use coax cable, they
just use a twisted pair of wires. :-)
Cheers,
Neal
Neal AB6G