Hi Ok, that gets you back to the basics of really major delta F / delta T slopes.
Bob On Aug 31, 2012, at 8:55 PM, Jim Lux <[email protected]> wrote: > On 8/31/12 7:06 AM, Bob Camp wrote: >> Hi >> >> An SC is going to have it's temperature curve centered up around 95C >> or so. If it's been cut as an OCXO crystal the turns will be up there >> as well. By the time it gets to room temp, the delta F / delta T is >> moving mighty fast. Think in terms of multiple ppm/C. A typical cell >> phone TCXO crystal is in the sub 0.1 ppm/C range in the vicinity of >> room temp. In addition, SC's are pretty hard to pull. For a normal >> TCXO (no DDS) something > 40 ppm of range would be needed. By the >> time you get the wide tune stuff in the circuit, the phase noise >> isn't going to be anything special. >> >> Bob >> > > We're not pulling the crystal.. we just let it sit. > What we do is change an NCO in the software radio implementation. Typically, > you have a coarse tune with a PLL in steps of 500kHz-1MHz, and then you do > the fine tune in software with a digital mixer/downconverter and an NCO > (which also is part of the carrier tracking loop). > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
