Impedance: Almost all RF connectors and cables are standardized for 50ω impedance. The only exception is generally the 75ω system, which is typically used for cable TV installations. It is also important that the RF coaxial cable connector has the characteristic impedance of the matching cable.
If this is not the case, an discontinuity is introduced and the loss can result.
VSWR (voltage standing wave ratio): Ideally it should be unity, good design and implementation can keep VSWR below 1.2 within the range of interest. Frequency range: Most RF work is now in the range of 1 to 10GHz, so the connector must have a low loss in this area. For cases above the time of more than 10 GHz-there is a lot of work in the range of things that are now in the area of a and a few-there is a choice of newer connectors.
They are expensive because it is the cable itself. Insertion loss: This is the connector loss within the frequency range of interest. Losses are usually in 0.1 and 0.3 decibels. Set how critical per watt (or fractional tile) is in most designs, even if such a small loss must be minimized and counted into the link loss budget.
It is particularly important at the low noise front end when signal strength and SNR are low. Operating cycle: How many connection/disconnect cycles can be connected to withstand and still meet their specifications? This is usually in 500 or 1000 loops. Threaded connectors, supplier-specified fastening torque are important factors in maintaining performance and reliability.