I was very impressed by the DVFO -II kit that I purchased in 1998 from S & S Engineering. A very well designed kit with a clean o/p, meeting most of my requirements in the shack as a reference & accurate VFO.
Since S & S DVFO-II kit uses a 16C57 Microchip PIC, an OTP device, I decided to build another DDS, with the main motive of plunging into the world of PICs using a more friendlier 'flash' PIC - 16F84, also from Microchip.
PICs have become very popular in the Amateur world and use of these devices in our homebrew equipment is inevitable. A wealth of information pertaining to design & programming is available on the WEB - all for free!!.
Having done a little research on the best (easiest ??) path to take, I chose 16F84 for my experiments; built David Taits's TOPIC programmer that works off the PC parallel port; ordered 'Easy PIC 'n' & 'PIC 'n up the Pace' PIC books, read little but spent a lot of time browsing the 'Net looking for DDS related projects.
DDS project - 'Building a Direct Digital Synthesis VFO' by Curtis W
Preuss, WB2V, published in QEX of July
1997 pages 3 to 7 is a good starter for
A DDS project - 'Building a Direct Digital Synthesis VFO' by Curtis W Preuss, WB2V, published in QEX of July 1997 pages 3 to 7 is a good starter foranybody interested in experimenting with DDS.
AD9850BRS with a maximum clock of 125MHz from Analog Devices is a popular DDS chip among Amateurs and is ideal for all HF work but it's successor - AD9851BRS, clocks upto 180MHz, has a 'x6' onboard clock multiplier, is better for HF and VHF projects. It also costs less than AD9850 and easily available at the time of this writing.
Using the following main Components:
16F628 PIC control, DDS and
Oscillator/ Output amp boards: