[time-nuts] HP-531xx calibrator nearing completion

Mark Sims holrum at hotmail.com
Mon Sep 11 11:47:11 EDT 2017

I connected a prototype of the HP-531xx calibrator signal circuits (input squarer, freq doubler, divider, output buffer, level shifter) to a TAPR TICC to see how stable the output was.  

This prototype was built on perf board using DIP packaged 74AC logic so I was not expecting good results.  Pleasant surprise...  very good performance!  There was no difference (within the limits of the TICC performance) in the calibrator xDEVs vs measuring the un-processed 5071A output.

The TICC was clocked by one 10 MHz output of a HP-5071A, calibrator by the other 10 MHz output.   TICC input was the calibrator output divided to 1PPS by a TADD-2 Mini.

I also checked the output waveform with a 5 GS/s DSO.   Rise time is less than a nanosecond.   There is around 50 mV (10%) of ripple on the top/bottom of the square wave output (expected with DIP packaged parts and point to point wiring on perf board).  Waveform symmetry is 50% (+/- the 200 ps DSO sampling rate).  

The calibrator output is quite a bit better than what the HP-59992 J06 produces... The J06 180 degree phase shifter is off around 24 degrees (6 ns).  It also degrades the rise time by around 1 ns.

Attached is a plot of the calibrator xDEVs
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