Construction of my version of G3XJP's STAR2 (Software Transmitter And Receiver) commenced after a QSO with my pal 5B4AGN. Bob was using his completed STAR2 rig on CW, and it sounded great.

The STAR operates on all bands from 160-M up through 10-M, on SSB and QSK CW.

After looking over the original Rad Com articles (20 in all), I started construction in 2007. The transceiver took about 16 months to complete.

The heart of the rig is a PIC-controlled DDS (direct digital synthesizer) based on an Analog Devices AD9951 chip. The AD9951 is a leading-edge integrated circuit with a 14-bit DAC output. The reference oscillator for the chip is a crystal-controlled and temperature-stabilized Butler oscillator. Alternatively, I clock my DDS with a Connor-Winfield 150-MHz module, courtesy of WA1FFL.

The DDS frequency is changed by means of a knob connected to a homebrew optical encoder. The encoder, in conjunction with the STAR's keypad, also permits changes to DSP settings and parameters. The DDS is mounted on a DIP plug-in to facilitate future upgrades. The module is shown here.

  
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The STAR uses an Analog Devices Inc. ADSP2181 DSP chip, with companion AD1885 CODEC. The IF in my rig uses an old CB radio IF filter as a roofing filter. In addition to the 16F876-20 PIC that handles the user interface, display, and DDS, the rig uses two additional PICs. One controls the highly accurate digital S meter and the other handles smooth timed T/R transitions.

The rig's mixer is a state-of-the-art switching design, originally developed by G3SBI, Colin Horrabin. In the STAR, a 4-transistor parallel JFET RF amplifier stage can be software-selected either ahead of the mixer or after it, for best noise-figure operation, or optimal IP3 third-order intercept.

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Here's the chief op at AI2Q using the STAR.

The image below that shows the rig's minimalist front panel. The STAR is almost entirely self-optimizing, and the only knob is that of the rotary encoder. The homebrew encoder disk can be seen lower right.

Click here for more details, downloadable files, notes.