[time-nuts] Oncore UT+

[alan bain]

Hello all,

I'm sure I'm not a time nut. But in the beginning I had an HP5245L and its
oven oscillator defined 10MHz in my corner of the world. Unfortunately one
day the oven heater stopped working.  And sadly HP didn't include an oven
temp stable indicator. So things started to go wrong when aligning a
spectrum analyser (somewhere in the GHz region where that 10MHz had been
multiplied up a lot).  As one might expect crystals designed to be stable
at 70 degrees C have a large temp-co at room temp.

A kind loan of an off air (Drotiwich) standard and HP53131A enabled some
element of normality to be obtained (and the oven fault to be found and
fixed) - interesting to see the HP200 style thermistor limited  oscillator
followed by envelope detector used as a temperature controller!  But of
course I was curious as to how the various oven oscillators in test gear I
owned actually behaved (such is the danger of having done a PhD in
stochastic processes). It's nice also to find non-Gaussian noise processes
cropping up along with the two sample variance.

A better reference was clearly needed. To convince myself I don't need a
Caesium standard I decided I needed a GPSDO.  I've been modifying one of
those Lucent RTFG-u REF-0 boxes following Peter Garde's excellent
instructions (because it looked fun).  All was going well until i found my
Motorola Oncore module believed to be a UT+ when bought was in fact a GT+
and didn't provide some of the T-RAIM messages the HP needs (the GT+ is a
navigation receiver).

There's not much info around on these modules (probably because they are
ancient) - and at the moment no UT+ listed anywhere in the UK for sale; so
wondering if anyone knows about the differences - are they firmware or
hardware?  There's a firmware upload option in the WinOncore software - but
I haven't been able to find any archives of the actual firmware.

Alan