SMA connector is outer conductor diameter is 4.13 mm, the characteristic impedance of 50 Ω, connecting mechanism for inch thread (external thread 1/4-36 uns - 2 a, internal thread for a quarter - 36 uns - 2 b) of the connector, usually with a 7.85 mm to 8 mm six-party coupling nut, according to the applicable situation, evenly distributed on the coupling nut has a minimum diameter of 0.41 mm wire three security hole, used to through the safety of the diameter of 0.38 mm wire, in order to improve the use of the SMA connector reliability.