GW4DGU Transmit-Receive Sequencer

This simple sequencer uses combinational logic with a time delay generator U1B, U1F. Pulling the input to ground causes the antenna relay output to go high, a few tens of milliseconds later, the amplifier/transverter output will then go high. When the input returns to the high state, the amplifier/transverter output goes low, followed, a few milliseconds later by the antenna relay. The input can be driven either from an external PTT line, and the transceiver driven from the amplifier/transverter output. If the transceiver is known not to generate transient outputs in the first few tens of millisecond after its PTT line is taken to transmit.

The sequencer is designed to operate on a standard +5V digital supply. The outputs go high (+5V) in the transmit state. Interfacing to the rest of the system is best accomplished via power MOSFETs.