SB-220 EasyKey - Softkey Alternative
Those who have done any research into modifications to the SB-220 have heard about Softkey. The primary purpose of the circuit is to reduce the voltage that your rig sees as it switches the relay in the SB-220 to the transmit configuration. It also reduces the amount of current that must be switched. Some transceivers, such as my Ten Tec OMNI VI+, would be damaged by the 120 volts that must be switched in the unmodified SB-220. Ideally, the voltage present at the relay jack of the SB-220 should be between 5 and 12 volts.
The Easykey circuit shown in the schematic below, does the job superbly. The simplicity of the EasyKey design is matched by its outstanding performance and reliability. An optical isolator protects your transceiver by keeping the high voltages isolated within the SB-220. When this modification is installed, 9 volts appears at the relay jack and the transceiver is required to sink less than 5 mA, which well within the capabilities of any transceiver. A kit is available from N4YG for constructing this simple circuit. The contents of the kit are shown below. It includes everything needed to complete this simple mod. Instructions, including photos are shown below as well.
EasyKey Schematic Diagram
EasyKey Kit Contents
EasyKey Assembled Board
EasyKey Installed in SB-220
