Old HP Gear - What Kind of RF Connectors Are These?

[fmashockie]

Hey y'all!  I am in the process of trying to repair my HP 8557A Spectrum Analyzer plug-in.  I want to perform some of the performance tests in the manual, which requires me to connect a sig gen up to preamp.  However, I cannot for the life of me find what kind of RF connectors HP used for this instrument.  They appear to be subminiature, but I am not sure what kind.  I tried SMA and SSMA but both were not right.  SSMA was definitely closer, but the male and female versions are opposite compared to the HP ones if that makes sense.  For example, the HP female connector is a threaded nut, whereas the SSMA connector I bought is a male inside a threaded nut.  I took some photos of the HP connectors for reference.  Would really appreciate anyone's help!!! So I can stop buying the wrong connectors!!! 

Thanks!

-Frank

[TimFox]

Those look like "SMC", a threaded connector similar to the snap-on "SMB".
Check dimensions with this site:  https://www.amphenolrf.com/rf-connectors/smc-connectors.html

[fmashockie]

Thanks Tim! I looked at the diagrams on the link you gave.  Measurements seem to match up.  For some reason I thought I read a chart stating that SMC was larger than SMA so I didn't think to check those...