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James Skalski wrote:
I am thinking about building one. Before I start gathering parts I figured I would check to see if anyone has started, fizzled out, or otherwise changed plans to build it. What parts do you have? Any completed modules? Jim n2go Would that be the DDS controled receiver design from the UK? His DDS-Micro design was in an ap-note on the Analog Devices web site (pdf download), but source code wasn't published. The specific pic micro he used is now obsolete, though similar chips are available (require software changes). Also the AD9850 dds chip he used is now somewhat long in the tooth. I am considering building a DDS vfo for a homebrew xcvr, but I am looking at using one of the AD9951 series chips. These clock to 400mhz and have a 14bit D/A vs the 10bit in the 9850. Spurs and phase noise should be quite a bit lower with the 9951 series chips over the 9850. You will need a surface mount to .1 mill spacing proto board to hand solder it (not to mention good eyes and/or a strong magnifier, and steady hands). Such proto boards are available on ebay sometimes, and can also be found for sale via a google search. I would also switch from the PIC processor to an Atmel MegaAvr mirco. The MegaAt16 and MegaAt32 processors are available in 40pin dip and 44pin surface mount packages. They have 28 i/o pins available if the on board JTAG interface is used for debugging. The JTAG feature and the support of the GNU C compiler makes these chips a better choice (IMHO) than the pics. A JTAG interface from Atmel sells for $200, but 'clones' are available for under $50 (and plans are available for building your own for even less. I have already built one). Atmel's Avrstudio is a free download for Windows (to drive the jtag) along with WINAVR (the gnu compilier and C library). Similar software is available for Linux from GNU/Sourceforge. |