How to Prevent Arcing in SMA Connectors

Read your component or device service manual for the recommended performance data of your SMA connector. Many connectors are rated for 18 GHz DC, and the coaxial cable should match or exceed this limit. Some connectors are rated for higher performance, such as 26.5 GHz, and should be matched to the coaxial cable. For instance, devices that output 26.5 GHz should not be mated with 18 GHz connectors.

Turn off the appliance, component or device attached to the connector cable. Locate the SMA cable connection that exits your device, appliance or component. The brass or aluminum connector should not be sitting against or on any metallic surface. Position the connector so that it hangs freely or rides along the floor or carpet on a non-conductive material. Use some electrical tape to cover the connector with several wraps, or route the wire away from bare chassis or metal framework.

Examine the SMA connector cable at the ends of the coupler points. The hot end is the cable nearest the working appliance or component power source, such as an amplifier or cable TV box. The cool end of the cable is the other side, which might lead to an antenna or speaker. Neither cable should have any visible twists or waves in the insulation where they attach to the connector. If they do, it means the cables were not stationary when screwing in the lug nuts. This can result in broken internal wires or cause excessive impedance.

Hold the end of the cable stationary while you manipulate the connector lug nut back and forth. First try to tighten the lug nut to make sure it seats. If it is tightened flush and you have slack or excessive play in the connector joint, it indicates the threads have worn past their usage criteria. If stripped, metal shavings can cause an internal arc. If a gap exists, it can also allow leakage and arcing outward. Replace the connector at both ends of the cable if this situation exists.

Uscrew the SMA connector by hand or with the aid of pliers. Remember to support the other end of the cable with your hand to keep it from twisting. Use a magnifying glass to examine the inside of the coupler that houses the male pin. Flick the end of the pin with your fingernail. It should be tight and not move. If it moves or detaches, it means the solder joint has failed and the connector must be replaced.

Examine the inside of the male and female connector base around the female socket and the male pin. Look for electrical arcing, which shows up as brown or black streaks from the edge of the socket or the pin and radiates outward. This indicates an arcing short. The interior insulated material should be clean and shiny, with no melted or bubbled appearance. Replace any such damaged connector.