I reported a few days ago that I had measured the return loss of one of the
female-female thrus supplied with my NanoVNAs when open at one end.
Measurements were made with an HP 8720D VNA with an HP 85052B calibration
kit. The return loss was 0.368 dB at 1.5 GHz, which is much higher than
the 0.05 dB or less I was expecting.
Kurt Poulsen had discovered much the same using his HP 85033C calibration
kit with the VNWA.
Today I was busy, but whilst I had a spare moment I put one of the
connector guages from my Maury Microwave SMA connector guage kit on the
female-female thru. This his 4 guages and can check
* Male pin
* Male dielectric
* Female pin
* Female dielectric
I can¡¯t recall what guage I picked up - it might have been for the pin or
it might have been for the dielectric. I can check again when I have some
time.
Anyway, both ends of the thru were mechanically out of specification. The
pin (or might have been dielectric) is protruding too far forward. The
amounts were quite small - one end 0.0005¡± and the other end 0.003¡±. But
the should *never* be precessed, as it can damage connectors you mate to.
There should always be some recession, but it should be as small as
possible. Recession on SMAs is typically 0.01¡±. This allows for
manufacturing tolerances to ensure there¡¯s no precession, which can damage
other connectors.
Anyway, just something else to be aware of. Not only is the thru
electrically poor, but it¡¯s mechanical properties are such that it has the
potential to damage connectors you mate it to.
Dave.
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...
Telephone 01621-680100./ +44 1621 680100
Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United
Kingdom
