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:

IMG_1530

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.

IMG_1529

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

IMG_1551

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:

IMG_1567
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.
IMG_1568
The only way to do this is to stack the components, below the LCD I’ve put the atmel 328p
IMG_1570
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
IMG_1571
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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