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Re: [Discuss-gnuradio] grGPS Preliminary Schematic

From: Daniel O'Connor
Subject: Re: [Discuss-gnuradio] grGPS Preliminary Schematic
Date: Thu, 6 Apr 2006 14:10:53 +0930
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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
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