On Thursday 06 April 2006 13:14, Martin Dvh wrote: > Why don't you use the usrp to generate your 16.384 or 32.768 MHz refclock. > Most daugterboards (except the tvrx) use this feature (They all use a 4Mhz > refclock on io pin 0. The only difference with your design is that you need > another frequency. The cyclone fpga in the usrp has internal PLLs which can > generate all kinds of frequencies. (They are not used at the moment) > > This way you would have a phase coherent system. > Which is very nice if you start to play with multiple gps daughterboards. > > You could then even play with modifying the refclock frequency to receive > other frequencies. (like the russian or the european GPS-like systems, > which are on frequencies near the GPS frequency)
Farnell sell 32.768 MHz crystals (They're not what you'd call cheap though - AU$17). Hmm they have 16.384 MHz ones for $12.81. Still not cheap.. Also, I think getting 32.768 MHz from 4Mhz with a PLL would be pretty difficult (if not impossible) -- Daniel O'Connor software and network engineer for Genesis Software - http://www.gsoft.com.au "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C
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