The spec for the 10811A's trimmer range is +/- 10 Hz, actually. Seems doable.
There was a good thread on the list back in late 2006 where some of the pitfalls of the DMTD technique in general were discussed. It seems that achieving optimal performance is a lot less trivial than anyone would like. If someone wanted to build a "minimum effort" system with a lower short-term floor than the 5370, my understanding is that it would require: - a 10811-class OXCO tuned to generate beat notes of several Hz - a mixer of some sort with good IF response down to DC - four good isolation amps (which thanks to Bruce's recent work is not a difficult or expensive issue) - some sort of delay compensation on one of the inputs may be needed to avoid decorrelation of the transfer oscillator's effect between the two channels - a sound card with good differential-phase stability Of course a 5370 or other two-channel TIC could be used instead of an FFT back end, but I'd be interested in seeing what level of performance could be expected with a sound card, too. Bruce, you were looking at differential jitter and delay on stereo sound card channels at one point, weren't you? If differential phase stability is a problem, then perhaps one of the channel IFs could be heterodyned up to a different carrier frequency that could share a single physical ADC channel. Isolation and phase-delay compensation would again be a big deal in any such scheme. Probably the heterodyne LO would need to be derived directly from the transfer oscillator. -- john, KE5FX > -----Original Message----- > From: [email protected] [mailto:[email protected]]on > Behalf Of Tom Van Baak > Sent: Sunday, August 02, 2009 9:14 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Methods for comparing oscillators > > > >A 1Hz offset may be convenient as its easy to adjust an 10811A or > > similar to achieve this. > > A 10Hz offset is harder to achieve. > > Would either of these be 10 Hz solutions? > 1) open the 10811 and change the xtal load capacitance, or > 2) change the oven temperature set point until the resonator > is 10 Hz off. You'd loose a little in tempco but... > > /tvb > > _______________________________________________ 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.
