[time-nuts] J06 HP-59992A time interval calibrator for HP-531xx counters

[Bob kb8tq]

Hi

This may be “inside” the envelope for something like a PIC. If not it’s a pretty 
easy task for any of the sub $10 FPGA boards. Given the relatively small 
audience, tacking an extra connector or three onto something might be the
better option. 

The big unknown (at least to me) is how close the signals need to be to ideal. 
If a few ns is “ok” it’s an easy task. If the spec is < 10 ps … not quite as easy. 
My guess is the 59992A is overkill, but to what degree? 

Bob

> On Jul 8, 2017, at 9:31 AM, Mark Sims <holrum at hotmail.com> wrote:
> 
> To do a full and proper calibration of the HP-53131/53132/53181 counters you need a J06 HP-59992A time interval calibrator... lots of luck finding one of those.   Looking at the manual, it is actually a fairly simple device which can be greatly simplified for the task of calibrating a 531XX counter.
> 
> The main task is to generate 10 MHz square waves with 50% duty cycle.  Four versions of the signal are generated (two positive and two with inverted phase).  One of four combos of these signals (P1-P2,  P2-P1,  N1-N2, and N2-N1) are driven to two output connectors.   The 59992A uses splitters and phase shifters to generate the signals and can handle analog signals.  The 531xx cal uses square waves so those signals can be generated digitally.   
> 
> My first idea is to take a 20 MHz oscillator and divide it by two to get a 50% duty cycle. One could also do something like squaring a 10 MHz osc with something like the Wenzel squarer... that would provide a more stable signal frequency wise but that might add some asymmetries to the signal.  Feeding the 10 Mhz osc through a doubler and dividing the squared signal might provide the best solution.
> 
> The 531xx cal procedure uses a +/- 0.50V signal.   I need a simple and cheap circuit to level shift the TTL signal to +/- 0.50V  It probably needs clean, stable, fast edges and able to drive a 50 ohm load (the manuals don't specify the required edge rates and load).   Any ideas for a suitable level shifter / buffer?  It would also be super nice if it could work from a single supply...
> 
> Also,  if such a cal board was laid out would there be any interest in making it available for others to build?  
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