Magnus Danielson wrote: > Look at the AD8561 datasheet first. The 74HC4046 is much slower than the > AD8561 and the higher output slewrate of the AD8561 is certainly good to keep > jitter down. The 74HC4046 is worse for that aspect. > > What I would rather critize Didiers schematic for is the lack of decoupling > caps. This is good for many reasons, but it includes keeping the rise and > fall times up and thus the slewrate up and thus the jitter down. > > There are decoupling caps everywhere, I kept the schematic simple. Same, the counters actual wiring is not depicted, it is straight from the Texas Instrument data sheet. I also have a 200 ohm pot across the OCXO output to adjust the drive level into the 390 ohm resistor not shown. > I would measure the actual phase-stability and phase-slope of the IF > transformer solution with aspect to temperature. You may want to lower its Q > value to flatten the phase-response. You loose in selectivity but gain in > phase-stability. > I have planned to do that. The transformer I am using is quite temperature stable, and the Q is controlled via the 390 ohm resistor, which may or may not be the optimal value from a Q standpoint. It is close to the best value from a drive level standpoint, to make sure I do not overdrive the comparator. I did not observe a measurable change in resonance frequency when blowing a hot air gun at it from a distance, even though my measurement method was crude (adjust the drive frequency using a SG503 and peak the voltage, use scope to monitor).
I could use the 5370 to measure the phase shift while I blow hot air on the circuit (transformer and comparator), or I could make a small hot box with a light bulb and a variac, put the OCXO and clock shaper in it and use my HP3478B voltmeter and a thermistor to record temperature, and plot delay and temperature via the GPIB while I crank the temperature, then I could plot delay vs. temperature. The opportunities to experiment are endless... I will never have time for all that, I better retire now :-) > Cheers, > Magnus > > _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts