I'm not sure why my stupid Explorer has eliminated the original message, but the jist is:
I've been working on the AD9912 DDS support to the dds_controller Yahoo group software, and other projects recently. But, I am now looking at supporting the Si570 again. This will come in two flavors: 1) Si570 WB6DHW board connected to a Bit Whacker. This will need to be the larger 18F2550 PIC version, as the smaller one doesn't have enough room for my code without some pruning. This is because I plan to treat the Si570 as just another DDS chip in the dds_controller group software. 2) Si570 as the master oscillator driving the AD9912 DDS chip. This brings some interesting possibilities. For example, you can move the DDS master clock around slightly to reduce spurs in the DDS. The DDS chip will generate the actual RF output, allowing very smooth frequency changes. While the AD9912 has spur-reduction technology, it is not clear that the spur reduction will be useable "on-the-fly" as you change the frequency. One ham that has played with some early spur-reduction code reports that it takes some fiddling with the spur reduction values to tweak the reduction at each frequency, and at least some spurs cannot the pre-calculated. Moving the DDS master oscillator may be simpler in the long-run. The dds_controller group's code has a lot of additional capabilites when using a DDS chip. It remains to be seen how much of this is useable with the Si570. So, the dds_controller code is being worked on, but not available yet. There is other code for the Si570 and Bit Whacker out there as well. Terry WB4JFI
