[time-nuts] Austron PRR-10 GPS discliplined Rb...

David I. Emery die at dieconsulting.com
Fri Jan 26 17:23:17 EST 2007


	I snagged (for $150 BIN, which might have been too much) a
Datum/Austron PRR-10 Stratum 1 Timing receiver complete with a LPRO
Rb... and two channels of GPS receiver/timing board (redundant, hot
swappable).

	These things use the Motorola Oncore family timing receivers 
(the latest version (rev G firmware) can support the M12M+) and are
primarily intended to supply precise timing for telco networks as DS1 or
E1 output signals with all the right bits set for timing purposes.

	There is a 4 channel "analog" output board available that can
supply 10 mhz, 5 mhz and 1 mhz (I found one of those too), but the
primary outputs in usual units one finds in the field/surplus are the
DS1 or E1 variety.

	The interesting thing about these units (which ceased production
in July 2005 - possibly because of the abandonment of the Oncore
receiver family by Motorola) is that they are the second kind of GPS
disciplined clocks - namely phase microstepper based designs which
accept a reference 10 mhz input and use a DDS chip to create a phase
rotated and frequency corrected version which is used to phase lock a 20
mhz VCXO and from that generate a new 10 mhz and 1 PPS.    This is in
distinction to the Lucent RFTGs which adjust the C field of the LPRO RB
to phase lock it to the 1 PPS input.

	Apparently the firmware measures the frequency offset of the 10
Mhz reference input (in my unit generated by a LPRO 101) and its
behavior over time and temperature and uses this to generate a phase
step correction for the DDS which results in a precise 10 mhz output and
1 PPS used to compare with the GPS timing receiver 1 PPS and adjust the
correction and its derivatives over time for optimum tracking.

	This means they can take a slightly off frequency but stable 10
mhz and make a precisely on frequency and even more stable 10 mhz locked
to GPS when GPS is available and open loop corrected  to the last GPS
offset values when GPS is not using both  measured frequency offset and
change of frequency offset with time (and I think temperature).

	I have a users manual (circa 2001) in .pdf format, but would dearly 
love to find a source of more detailed documentation - the things are full
of jumpers and stuffed/not stuffed options and it would be nice to know
much more about them.

	They do, however, provide some ADEV data on the quality of the
input source as one of their data outputs available from the RS-232
port and as such are kind of neat...
	
	
-- 
   Dave Emery N1PRE,  die at dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in 
celebration of what could have been, but wasn't and is not to be now either."




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