"Bryan" wrote in
:

....
cutters. Most coaxial cables exhibit a capacitance of about 30pF/ft,

50 ohm cables with solid PE dielectric ALL exhibit a capacitance of about
30pF/ft. It is not a coincidence, C/unit length, Zo and velocity factor are
all related.

That method of estimating the capacitive reactance of an o/c stub (for that
is what you actually have) is only accurate for very short stubs.

Capacitors fabricated from coaxial transmission line are often much lossier
that quality fixed capacitors, so they should be used with care.

Owen