[time-nuts] Lucent RFTG-m-XO ...

[Dr Bruce Griffiths]

geo wrote:
> Hi Jason,
>
> perhaps i am the only "german", currently available. My english is not good
> but i hope, it's less pain for you to read my "english" than to read the
> german text ;-)
>
> Best regards
>
> Martin Bertges
>
>
>
> Description of Lucent RFTG-m-XO GPS frequency standard
> ver. 20.03.2007
>
> Introduction
> The Lucent frequency and timing modules (modul number RF(T)g-m) had been used
> in GPS basestations for synchronization; there are various models available
> (quartz / rubidium or GPS based), made from 1998 to 2000; no official manuals
> or descriptions are available but the parts are described in newsgroups and
> amateurs like "time-nuts" have collected a lot of information (which is
> available in emails only, with a low "signal-to-noise ratio"); 
>
> i have analysed and expanded this information, based on own observations;
> I will describe the RFTG-m-XO in details: it is a so called "GPS disciplined
> frequency standard" or GPSDO; that means the local OCXO is "disciplined"
> by the GPS based 1PPS signal on using a microcontroller; the OCXO parameters
> (like temperature drift and aging) are determined and the control voltage
> of the OCXO is calculated and applied; a "holdover status" is possible,
> when sufficient GPS signals are not available; so the resulting accuracy of
> the 1PPS/15MHz signal is much higher than based on a single quartz oscillator;
> the GPS receiver is a well documented Motorola VP Oncore;
> the GPS receiver's serial data (position, time and status) are internally
> as TTL signals available and can be used with TAC32 or other programs; 
>
> output:
> via the serial interface (J6) time and status are transmitted once per second;
>
> (the text following should be read from the JPEG file ;-) )
>
> Character 1-4 are unimportant, 5-6 are status, 12-19 shows GPS second (in hex 
> format since 6.Jan.1980), 20-23 version number, 24-25 checksum;
>
> (the descriptions of the LEDs, J4/J6/J5/J3/J7/J2 and P1 are in english ;-) )
>
> Connector J6 holds 1PPS output with a standard deviation of about 30ns compared 
> to UTC; can be used for clock comparison or NTP server synchronisation; 
> J6 pin1/2 holds a RS485 signal for longer transmission lines;
>
> there is also a sine signal available with a SMA connector (15MHz); this signal
> is based on the GPS controlled 10MHz DCXO (?); the latter can be identified
> easyly (should be buffered, when used for own purposes) frequency accuracy
> is about +-E-10 (tracking);
>
> Operation is easy; after connecting 24V DC on P1 and a GPS antenna on J7,
> the ON-LED show green light after about 15 minutes, indicating enough 
> satellites; the output signals are valid then; to get a good "holdover"
> performance a longer operation period is neccessary;
>
> Sources:
> time-nuts-mailing list http://www.febo.com/pipermail/time-nuts/
> Motorola Oncore http://www.corallinks/tmbroker/images/oncore_eng_notes.pdf
>
>
>
>
>
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>
>   
A slight correction
First phase should read:

The Lucent frequency and timing modules (modul number RF(T)g-m) had been used
in GPS basestations for syntonisation/synchronization; 

Bruce