Hi The Analog Devices data sheet shows the maximum input clock as 75 MHz on the DDS chip. There is no clock multiplier on this particular DDS.
Bob On Jan 24, 2010, at 4:56 PM, Dave Wade wrote: > > > k5nwa wrote: > > At 12:04 PM 1/24/2010, you wrote: > >> > >> Thanks for your explanations, Bob! > >> > >> I understand the principles of driving the mixer with a squarewave > >> signal and that you use a comparator to change sine to squarewave. > >> > >> Where I'm failing at is the trick how to receive 30 mhz with a DDS > >> that make 37 MHz max without getting problems with nyquist. Can you > >> use a comparator to double your VCO frequency without getting > >> problems at the duty cycle? > >> > >> > >> Stephan > >> > > > > This is a mixer, you are not trying to digitize the 30MHz signal > > where you would need a minimum of two samples, instead you are mixing > > it down to the base band. > > No but the DDS chip is synthesising a sine wave from samples, and > Nyquist bite both ways. However some DDS chips (I don't know about this > one have on-board frequency multipliers... > > > > > > > Cecil > > k5nwa > > www.softrockradio.org www.qrpradio.com > > < http://parts.softrockradio.org/ > > > > > Never take life seriously. Nobody gets out alive anyway. > > > > > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > > > > > > >
