SMA and 3.5mm are matable connectors. The SMA connector is an economical, lower performance interface. Mechanical tolerances, stability, temperature performance, SWR, repeatability, loss, and wear are all much better in the 3.5mm interface.
It is easy to see which type a connector is by looking at the material surrounding the center pin. SMA type will have a foam bead, while 3.5mm uses an air interface.
Due to cost, the 3.5mm connector is most often used in metrology applications, whereas the SMA connector is used for production. Because of this, it is not uncommon to see wear and tear degrade the SMA to the point of damaging mated connectors. Extra care must be used when mating SMA onto 3.5mm due to the cost of the 3.5mm connectors. Be sure to gauge SMA as well as 3.5mm to prevent protruding SMA pins from propagating damage.
Revision 2.0 17 Jan 2000 lae