Quoting "Whitaker, Brian" <[EMAIL PROTECTED]>: > Humph... > > I think maybe the answer to this is that 100kHz is outside of the loop BW of > both of these applications; this means the the phase noise is really just a > function of the VCO itself. I would have expected that the inherent phase > noise of the 2118's VCO would have been worse than the 2740 (for the Kvco > alone)... so I'm guessing that the 2740's VCO just plain stinks. In Maxim's > defense, it's a really old part (pre SiGe, even!) > > So remember that the close-in phase noise is mostly dependent on the > reference and the noise generated from the PLL itself (FM modulates VCO, > lots of noise + high tuning gain Kvco => higher noise in PLL BW). It's > pretty tough to compare phase noise unless you know about the references > used and the loop BW and such. >
I'll try to trackdown information about the respective PLLs. > I had always thought that a USRP board from one of these sat tuners would be > a good general-purpose receiver... but Krys has the Microtune TV tuner > boards done already -- I'd suggest working with those and just see what > issues people run into in trying to use this for GPS. > I had nothing to do with the Microtune tuner boards, but I'll take the credit :) > Also -- I'd suggest not designing a USRP board around the 2740. There are > better front-ends out there. > > One last thing -- Krys, you said something about the 2116/8's not needing an > external reference? Pins 21/22 are for the XTAL -- the part has an internal > reference oscillator, but that just means that we provide the positive-fb > amplifier that rings against the (passive) crystal. Tuners that don't have > this require a 'reference oscillator' (often 'TCXO') module that includes > the passive resonator along with the active oscillator circuit. IC mfg's > are busy trying to design out everyone in the app ckt they can, but no one > has built an on-chip crystal reference :) > I meant that the 2116/2118 Evaluation Board does not need an external reference, while the 2740 Evaluation Board does. What is the price of the 2116/8 Evaluation Board? > Brian. > <snip> _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
