Anders Time wrote: > What is the best way to generate a very stable 10.001MHz(low E-13 or > -110dBc/1Hz) to be to do high resolution heterodyne(Allan deviation) > measurements? > Using DDS? > Using PTS 500 or 250 synth and divide? Using HP 8662A and divide? > Some smart pll circuit by locking the 1000Hz to the reference in some way? > Thanks > Anders > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > Anders
Its far easier to produce 9.999MHz cleanly than 10.001MHz The simplest and quietest way is to use a pair of cascaded SSB mixers: The first SSB mixer is an LSB mixer that subtracts (10MHz / 100) from 10MHz to produce 9.9MHz. The second SSB mixer is a USB mixer that adds (9.9MHz/100) to 9.9MHz to produce 9.999MHz. i.e. 10MHz*(1 + 1/100)*(1-1/100) = 9.999MHz Follow the USB mixer with a cleanup PLL using a low noise OCXO, however you will need a custom crystal. This is why NIST used a 10Hz offset with a 10MHz input and NIST + JPL use a 100Hz offset with a 100MHz input no custom crystal is required its easy enough to offset a standard 10MHz OCXO by 1ppm. Process is similar: 9.99999MHz = 10.00MHz (1-1/1000)*(1+1/1000) One could also use a USB mixer 10.001MHz = 10MHz*(1+1/10,000) but it may be more difficult to filter out the residual 9.999MHz component in the USB output. Synthesizers seem attractive, but in practice they have lots of spurs that can interfere unless you choose a suitable offset like 123 Hz as adopted by JPL to minimise synthesizers spurs when using a commercial synthesizer. Bruce _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
