Interface Circuit for Alinco DX-70 to SGC Tuner

The device operates by waiting for the tune button to be pressed , start the transmitter, and wait for the SGC tuner to finish its job using the DX-70 and SGC-239 tuner working together.

During the construction and implementation, the PCB route was chosen to keep the board as small as possible and a small plastic enclosure is designed around. A single-sided PCB was chosen with only one jumper wound up. The piezo element is the black round device towards the bottom of the board. Without this interface in circuit, it would be possible to supply power to the tuner by arranging the signal lines from the two DB-9 connectors with opposite gender. The antenna can be tuned without this interface by supplying steady RF to the tuner although all status feedback would be lost and the transmitter would be manually keyed using a switch or CW key.

A minimal amount of circuitry is involved since all the activities are handled by the PIC16F84 microcontroller which receives signals coming from the tuner and a few from the transmitter. With the provided firmware, the MCU does not need to be programmed.

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