[time-nuts] HP 1938 revisited

wje wje at quackers.net
Sun Apr 12 21:08:19 UTC 2009

Fluke.l (China) was selling a number of 1938's on Ebay. I snagged one 
just to have a piece of HP history.
It works just fine, but I've noticed something a little strange.

Comparing the 1938 to both my cesium and GPS standards, there's a 
distinct periodic 1ns phase shift every second. Seems to smoothly 
advance  1ns for 500 ms, then retard back to the original phase point 
over the next 500ms. Question: is this to be expected? I'm assuming this 
is from the AFC loop, but I would have expected it to be better damped.

I've searched both this group and the HP group; there really doesn't 
seem to be a great deal of info about these, other than schematics and 
some nice variance plots on leapsecond. Just what is the serial port and 
the PIC data lines useful for, if anything?

Bill Ezell
They said 'Windows or better'
so I used Linux.

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