Frequency synthesizer project

Model 1 was built to test the capabilities of the AD9851 chip, and to optimize the code. Model 2 is the miniaturized version so that it becomes an instrument in the shack.

Model 1

The design is based on the AD9851 chip including an atmel 328p with the Arduino bootloader. And of course I use the Arduino IDE:


Top view: AD8951 with a 30 MHz oscillator, I turned the internal 6x multiplier on. There is a jumper for turning the LCD backlight on/off, perhaps I will replace this with a n-channel MOSFET switch.


The rotary encoder includes a push button, the LCD lists the frequency and the increment setting.


Attenuation of 30 dB is enough for direct input to the airspy/spyverter which I use as a calibrated spectum analyzer.

The design of this DDS mostly follows from the instructables website. There is a todo list for this project:

  • Find a case, right now it is half the size of a Velleman PCB.
  • Increase the output level to perhaps 5 Volt
  • Investigate whether I can turn this into a VNA

Model 2:

Miniaturize model 1 so that it fits in a Hammond case, the idea is the same, except that I use 3 mini voltage regulators and that I stack the LCD display on top of the atmel 328p chip.  Also I rewired everything because of the space restrictions. In the end I got this:

The DDS in its mini Hammond box, the window in the lid is a bit critical, but it always turns out to fit. (Use tape and take your time to make the window.
The only way to do this is to stack the components, below the LCD I’ve put the atmel 328p
So this is what you get at the lowest level, mind the three mini 5V regulators. The board takes 100 mA from a 9V battery
And this is the exploded view, not the piece of foam to keep the 9V battery in place.

Last update: 20-dec-2017


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