.. I have had trouble controlling the > WB6DHW board probably because of RF feedback and bad grounding on my > part.
I've also had this same problem while controlling the Si570 chip from the PC parallel port. The symptom was the chip not giving out the correct frequency or simply not obeying to the software. The problem went away after I added 33pF capacitors at the SCL and SDA inputs (header H2) in WB6DHW board. The capacitors leads must be as short as possible, SMD types are prefered. The 33pF value is good to the intended range (10-200 MHz), a higher value may distort the shape of the parallel signals. It now works smoothly, I specially enjoy SWLing using I2PHD's Winrad which does a fine job of controlling the 570 chip with PE1NNZ's DLL. 73, JK De Marco, PY2WM
