On Fri, 2011-01-07 at 10:01 +1100, Matt Robert wrote: > Hi Guys, > > I ran Kalibrate against my pair of USRP1's using GSM900 towers (around > 940MHz) and found my first unit to me 5kHz off and the second was 13kHz off. > > Is this within limits for the built in oscillator? I have been using > them to transmit P25 frames around 435Mhz and found that my commercial > P25 radios will not decode anything coming from the second USRP. The > first USRP works OK. I have swapped around all daughterboards between > both USRPs and the only common factor is the second USRP motherboard so > I am sure its due to the clock in that unit. >
This is within spec. It doesn't tend to drift that much so if you characterize how far it's off it'll stay reasonably constant (to a few ppm) unless temperature changes drastically. > Perhaps clocktamer or a secondhand GPSDO is needed for my Tx applications. You will need an oscillator with a ~64MHz output to run the USRP1. There is no 10MHz reference input on USRP1. I used a GPSDO and a homebrew PLL based around an Si570 VCXO to keep mine synchronized, but it wasn't a quick hack. Unfortunately there don't seem to be many 64MHz TCXOs in a reasonable form factor out there. --n > > Cheers, > Matt > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
