Hi I've used the 6790 for this sort of thing before. It's a good choice since the whole signal chain is synthesized (if I remember correctly ..). It's still going to be tough to hit the originally requested accuracy with one.
Bob On Jul 26, 2010, at 6:34 PM, Murray Greenman wrote: > You guys are trying to crack a nut with a sledgehammer! > > For a start, as Didier says, you can't possibly read the frequency of a > sky-wave signal to 0.01Hz in any short time frame since the Doppler on > the signal can be as much as 1ppm (i.e. 10Hz at 10MHz). You can only > infer it closer than that by studying the frequency in the very long > term. > > In addition, you'll never know how much of the daily variation is > ionospheric, and how much is due to thermal changes at the source. > > For what it's worth, the method I use for HF frequency measurements is > much simpler. I use a receiver which I can lock to my GPSDO (RACAL > RA6790/GM and HP Z3801A), and thereafter calibration is simply an issue > of getting the sound card sampling rate correct at the software spectrum > analyser, which you can do with a 1kHz reference from the GPSDO. No > complicated signal generators, signal injection, or AM mode with AGC > problems. > > I use Peter G3PLX's SBSpectrum as the analyser, where you can trim the > sample rate in tiny steps. It also has a frequency resolution of 25mHz, > which is more than adequate for HF. My combination has won FMCs, but I > still can't resolve 0.01Hz off-air. > > Whatever you do (with a sky wave signal) must be done over a long time > frame in order to be sure of getting closer than 1ppm. > > 73, > Murray ZL1BPU > > > _______________________________________________ > 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.
