[time-nuts] What to do with your dead cesium

[Skip Withrow]

Hello Time-Nuts,
Well, with the COVID-19 stay at home order I have been working on a
couple of projects (at home).

This post shows what I have done with an old FEI FE-5440A cesium
standard.  The tube was dead, so I decided to turn it into a GPSDO.  I
ripped out the tube, HV supplies, modulator, and OCXO.  The battery
was already missing, so it was replaced with a couple of SLA units.  I
decided to use a TruePosition GPSDO since it was small (I just wish it
had a LOCK indicator).  An SMA antenna connector was added to the rear
panel.

Basically, the 10MHz from the GPSDO feeds the distribution system in
the FE-5440A.  The TruePosition 1pps was brought out to the front
panel, and can be used to synchronize the clock in the unit.  An
RS-232 DB-9 was put in place of the C-field control so Lady Heather
can monitor.

Some of the nice features are:
10MHz, 1Mhz, 100kHz, 1pps, and 1ppm front panel BNC outputs.
Front panel clock display (that is easily set from the front panel)
1pps (FE-5440A) can be offset from 0-1 sec in 100ns steps from the
TruePosition 1pps
Battery backup (greater than 2 hours) and DC input, as well as AC input

I don't know about the phase noise performance, but ADEV is probably
better than the original standard (as long as there is a GPS antenna
connected).

I have attached a couple of pictures of the unit plus a 5-day TimeLab plot.

Regards,
Skip Withrow
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