I had a lot of fun operating low power with my Yaesu FT-817 portable HF transceiver, but have often wished that it had some audio or RF processing to add a little SSB punch. There are some excellent audio processing access – sories available commercially, but I thought this would make a great home-brew project reminiscent of the early Heathkit days. With this in mind, I began to look for suitable building blocks to bring this idea to life.
Allen Baker, KG4JJH
The VocalMaster is a speech processor specifically designed for the Yaesu FT-817, although it can be adapted to work with other radios. It features fast or slow release time, adjustable noise gate, compression ratio, and limiting threshold. The unit is powered by the rig and adds some SSB punch to your QRP station.
Drawing (pdf file)
Schematic (pdf file)
Headset adapter (pdf file)
PCB Layout (master pcb file)
Conclusion
I am delighted to report that all of the design goals have been met. The aluminum enclosure is smaller than my FT-817 and provides good shielding. All components mount on a printed circuit board, including
the microphone connectors. An LED output level meter provides visual feedback, and a built-in signal generator simpli?es antenna tuning. As an added bonus, the Yaesu FT-857 and FT-897 also use the MH-31 microphone, so the processor can be used on all three rigs. On-the-air reports with the FT-817 have been very favorable with an average 6 dB increase in signal strength. The VocalMaster will enhance your SSB signal and you will be proud to place this eye-catching accessory next to your rig. Once you have rounded up all of the parts this project can be completed in a weekend, so heat up your soldering iron and give your QRP station some pizzazz.