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

[Rob Kimberley]

Ulrich,

I'm absolutely certain that this is how they did it. My old boss the late 
Bob Ellis made a big point about this being a new way forward that didn't 
involve any direct tuning of the Rb. You let it free run and correct using 
the DDS technique mentioned. The rational was that this way you got on the 
desired frequency quicker than the traditional PLL methods, which was a big 
plus when installing these in Telco sites, as time was at a premium when 
installing and testing the systems.

Rob


----- Original Message ----- 
From: "Ulrich Bangert" <df6jb at ulrich-bangert.de>
To: "'Discussion of precise time and frequency measurement'" 
<time-nuts at febo.com>
Sent: Saturday, January 27, 2007 12:32 PM
Subject: Re: [time-nuts] Austron PRR-10 GPS discliplined Rb...


Rob,

are you absolutely sure it works this way? I experimented a lot with a
48 bit dds chip from analog devices for a GPSDO just to learn that THIS
way worked not good. What however works good is to imagine the
combination of OCXO and dds as kind of 'pure digital efc'. That is: The
output of the DDS (and not the RB's) is divided doen to a 1 pps which is
phase compared to the gps receiver. This makes the system an overall PLL
closed loop as seen with conventional efc circuits, however without the
need for precise analogue circuitry, which is why i use it!

Best regards
Ulrich Bangert, DF6JB

> -----Ursprüngliche Nachricht-----
> Von: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Rob Kimberley
> Gesendet: Samstag, 27. Januar 2007 09:39
> An: 'Discussion of precise time and frequency measurement'
> Betreff: Re: [time-nuts] Austron PRR-10 GPS discliplined Rb...
>
>
> I remember them well...
>
> Have sold them and installed them for Telco customers in
> Europe when I worked for Datum in the mid 90's. Novel design,
> and as you say they don't attempt to correct the Rubidium,
> but compare its output against GPS and use DDS to make the
> correction. In practise they worked very well and provided
> excellent Stratum 1 references.
>
> Unfortunately I don't have any documentation, but have some
> of the blanking panels and other bits of hardware lurking in
> the store room here. Will have a hunt around, and see exactly
> what's available to anyone interested.
>
> You got yourself an excellent bargain!
>
> Rob Kimberley
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] On Behalf Of David I. Emery
> Sent: 26 January 2007 22:23
> To: time-nuts at febo.com
> Subject: [time-nuts] Austron PRR-10 GPS discliplined Rb...
>
> 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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