For those on this list first venturing into the v.h.f. and u.h.f. regions
and who would look for repeatable results down around minus
50dBm and quibble over a tenth of a dB, BNC is not the way to go.
FWIW, calibrating 50kHz to 100MHz with these 34cm SMA-to-BNC pigtails:
.. and a generic BNC terminator and female coupler
yields lower CH0 LOGMAG when subsequently remeasured (-68 to -81dB)
than do included SMA cable and terminator (~ - 63dB)
For 500-900MHz
CH0 LOGMAG with BNC pigtail remeasured after cal yields -47 to -51 dB
while remeasuring SMA pigtail after calibration yields -68 to -73 dB
For frequencies of interest >>to me<<, BNC appears better..
Oristo