Dirk, ON4ADZ wrote: "I want to switch a mentioned SB220 rated at 125VDC@80mA." ========== Connect the TX GND jack on the transceiver rear panel to the ANT relay jack on the SB-220 rear panel. Set the LIN OFF/ON switch on the transceiver rear panel to the ON position. That's all you have to do. The relay in your Mk V will handle it ok. 73, de Earl, K6SE