At 09.29 19/10/2007, you wrote: >Very informative Bodo! > >Lesson learned: >Synthesizer design is black art. Consider using a traditional >bank of switched crystals instead of that "high-tech" stuff! :-) > >73 >Johan SM6LKM
Dear Johan, Well, not black art, but one must know what he is doing and be equipped to measure the results. Possibly the best way today is using the last generation of DDS chips, like the AD9912. It requires a 1GHz clock, but all in all the circuit seems to me simpler and les critcal than a serious PLL of similar performance. More, the output is very clean even at 144MHz. It could be a good LO for that band too. I did some preliminary measurements on the AD9912 synth by I0CG. The results are in the file sectin, under AD9912. Measurements done with an HP 8568B (the cleanest SA that I have...), DDS tuned at 180 MHz, 0dBm output. All spurious signals seem due to the spectrum analyzer, possibly except a weak 100MHz signal. More info are in the SDR_ITALIA Yahoo group, under "AD9910 - AD9912" folder. Giuliano I0CG is working on a kit built around the AD9912... stay tuned ! 73 - Marco IK1ODO / AI4YF
