John Miles wrote: > If you don't want pushbutton convenience, you can measure the close-in phase > noise with not much more than a $5 mixer and $2 opamp. It will take a lot > of "sweat equity," and you will need to build two of whatever you're > measuring, or buy/borrow a known-cleaner source at the same frequency. > > TSC analyzers are great but they are not the only way to go. Actually their > biggest advantages lie in their size/weight and the fact that the reference > doesn't have to be at the same frequency as the DUT. Other than that, their > performance is not necessarily better than a homebrew single-mixer > quadrature PLL or an 11848A. > > -- john, KE5FX > John
For compatibility with the PLL technique a trimmer and EFC is required. Using back to back varicaps is supposed to minimise the effect of varicap noise on the oscillator phase noise. The next step below using a cross correlation technique is to use a low phase noise frequency multiplier to decrease the system phase noise floor. A good multiplier can have a significantly lower phase noise floor than a mixer in the flicker phase noise region. Another candidate for evaluation would be an oscillator using a low phase noise modular amplifier with 50 ohm input and output impedance. A splitter is used on the amplifier output to extract a useful signal. Lumped component 1/4 wave lines are used on the input of the modular amplifier and the feedback output of the splitter to achieve a match to Rs/2, where Rs is the crystal series resistance. A full wave diode clamp can be incorporated to limit the crystal dissipation. A phase noise of -156dBc/Hz @100Hz offset has been achieved with such an oscillator. Bruce _______________________________________________ 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.
