29 January 2014


The discussion and web-xcitement around the MINIMA transceiver designed by the BITX author added yet another project to my to-do list. Before buying an Si570 for MINIMA, I still had to play with an AD9850 DDS board I recently bought.

Wiring it up to an Arduino Nano clone was a matter of half-an-hour. A working Arduino sketch was easy to find thanks to the work done by AD7C: in an hour my DDS signal generator was up and running.

The code is simple and gets the job done. I did a few easy changes:
  • corrected the "MHz" label (was "Mhz")
  • delayed the store timing of the latest tuned frequency (2s, now 20s, not to stress the uC EEPROM)
  • added a visual feedback whether the latest frequency has been stored or not
Even to my non-calibrated frequency counter, the DDS frequency was off by ~ +50 Hz. This was corrected with a simple math that I will describe in the future.

To my surprise the whole circuit draws about 165 mA: that's a lot of current! That's 0.8 W or power consumption. Even if the AD9850 DDS offers a huge frequency agility in an HF RX/TX, that's at the expense of current consumption. I will not give away my QRP frequency XTALs just yet!