[time-nuts] Rubidium for HP 53131A

Bob kb8tq kb8tq at n1k.org
Mon Feb 19 17:21:24 EST 2018


Be careful about air flow. Those counters have heat issues even in the stock configuration.
The Rb is a bit of a power hog so it heats up as well. Not saying it won’t work, only that
you need to be sure the air is moving in the right places.


> On Feb 19, 2018, at 4:18 PM, Skip Withrow <skip.withrow at gmail.com> wrote:
> Hello Time-Nuts,
> A while back I acquired an HP 53131A, and a bit later added one of the
> Chinese knock-off 3GHz prescalers.  Makes for a nice counter except
> for the very poor standard timebase.  So, While researching the Option
> 010 and finding how outrageous the prices are running I found an
> Option 010 DIY project.  It occurred to me that I could just
> substitute a Symmetricom X72 rubidium oscillator for the ovenized
> It came out really nice (and is much better than an Option 010 - at
> least for anything over 10-100 seconds).  I have a header so that I
> can calibrate the oscillator over the serial port (a one-time exercise
> I imagine).  And I added a LOCK indicator in one of the removable
> plugs right above the reference BNCs on the back panel.  Both the
> oscillator and the LOCK light are powered from the always on +12V so
> there is no warmup when the counter is turned on and the LOCK
> indication works when the counter is powered off.  And since the fan
> runs 24/7 I'm not too worried about the X72 overheating.
> All the extra hardware is mounted on a simple 'L' shaped aluminum
> plate that bolts where the Option 010 mounts to the chassis side rail.
> I used a 16-pin flat cable that plugs directly into the 53131A main
> board.  The only modification that was made to the stock counter was
> to drill the hole in the plastic plug for the LOCK light.
> Now the Reference Out can also be used to drive other devices as well
> (with reasonable accuracy).
> Relatively easy project that can be assembled in a weekend .
> Pictures are attached.
> Skip Withrow
> <sRb Mod-1.jpg><sRB Mod-2.jpg>_______________________________________________
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