[hpsdr] synthesizers.

[FRANCIS CARCIA]

Hi All,
  I was looking at the LMX2486 and LMX2485 on the National page. This looks like the newest fractional n machine and pretty easy to use. I would think this chip into an op amp driving a VCO with 15 or 20 volts of control range would make a great source. A string of dividers off the VCO would allow 1 HZ tuning and low phase noise. I bet this would be cleaner than any DDS. The national site has design software to pick filter components. The only problem is the output voltage swing is low so an op amp would needed to have some gain to drive a wide band VCO. This looks a lot easier to do than the analog compensated fractional n.  
  frank 
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