> Magnus inspired me to try my own cross-correlation experiment with the > TimePod today. I used two fairly normal OCXO frequency standards as the > reference, and a Wenzel 5 MHz ULN as the device under test. > > By doing single-reference measurements of each OCXO versus the ULN, I > was able to plot their noise. Since the ULN has performance near the > noise floor of the TimePod, I could then test how well the correlation > works to allow measurements below the noise of either reference. > > Conclusion: it works *really* well. Plots and a little write-up are at: > http://www.febo.com/pages/cross-correlation/index.html
Cool stuff. That's an impressive ULN -- I've never seen one do -125 at 1 Hz before! The oscillators used for dual-reference measurements don't have to be especially great. The 10811 in your 5061B is probably a lot quieter than the -155 dBc/Hz floor imposed by the 5061B's buffer amp. As happened in your plot, the worse oscillator of the pair has the most influence over the noise floor at a given offset. They don't need to be matched in performance. (BTW, something's funky about the way your images are getting scaled... in both Safari and Firefox, they seem to want to take on the aspect ratio of the browser window itself, which I've never seen before. Is that intentional? It makes them look oddly squashed unless the browser window proportions happen to be just right.) -- john, KE5FX www.miles.io _______________________________________________ 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.
