Ulrich Strictly for adjusting and comparing two 10 or 5 MHz sources I use the circuit from the Austron 2110 that takes a 5 MHz input and through mixing generates 5.0005 MHz subsequently devided down to 1.0001 MHZ. Mixed with the other input at 1 MHz the resulting difference is 100 Hz which any decent counter can resolve to nine digits. Works for me and often I just use the Racal 1992. At one time I used the multiplier chain out of a couple of FTS 4050 Cesium's but found the above more convenient for strictly tuning purposes. Bert Kehren Miami In a message dated 1/5/2011 3:18:52 A.M. Eastern Standard Time, df...@ulrich-bangert.de writes:
Bruce, I had the same idea as you and my friend Frank and I performed the following experiment to check whether it is possible or not: Two brick oscillators (I believe to remember in the 8 GHz region) were locked to the same source (HP8660) in the 100 MHz region which in turn was locked to my local 10 MHz reference (Z3805). The two signals were mixed down to DC with a M14A mixer. By means of a phase shifter in one of the cables we were able to change the phase between the signals and so to determine the mixer's sensivity as a phase detector. The mixer's output was sampled with a HP3457 at a one second sample rate. The voltage measurements were then re-computed into phase fluctuations and this data was fed into my PLOTTER utility to compute what must be considered the AD noise floor of this system. I have not documented the results but I remember that the noise floor indicated a clear improvement against a direct phase comparison at 10 MHz for a given TIC resolution. What you suggest will produce you a mixer output signal which (when looked at with a scope) will easily enable you to trim your LPRO within seconds. If you can lock the bricks directly to 10 MHz this is even better. I have been thinking to use this scheme as a general tool for oscillator stability measurements. Since we must consider that two odcillators may not always be THAT close to each other in terms of frequency it would be better not to mix to zero but to a beat freaquency of say some 1-100 kHz (depends of course on the brick's pull range). This would involve a offset generator for one of the signals. I have drawn a circuit but not actually built that uses a ADF4002 and a DDS block to lock a 100 MHz signal to a 10 MHz signal where the DDS will provide the possibility to offset the 100 MHz signal in small amounts. I plan to lock two low noise WENZEL 100 MHz OCXOs to the 10 MHz sources with one of them with a small offset. Then these two 100 MHz signals are compared after being multiplied by the brick oscillators (I have two bricks that translate 100 MHz to 10 GHz). Perhaps the group can comment on the feasibility of the plan. Best regards Ulrich Bangert _______________________________________________ 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. _______________________________________________ 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.