Hello and greetings to the list, I'm a new member and would like to report on my efforts in controlling the rubidium oscillator in the Lucent RFTG-m-RB module. I've been sifting through the time-nuts archives but haven't found any success stories on this apart from the original setup consisting of RFTG-m-RB and RFTG-m-XO. So maybe my experiences are of interest to those with a standalone RFTG-m-RB. In short, it seems to be possible to discipline the oscillator inside the module if pps signal and accompanying time tags are applied to socket J5. The pps should be of TTL level and the time tags must be of the form of the Motorola Oncore "@@Ea..." message. This message is described in the Oncore manuals so I won't go into it here. The time tags must go to pin 4 and the pps to pin 9 on J5. In a first approach, the pps was taken from an Odetics GPStar "time and frequency system" and the time tags were provided by a program running on a PC with a sufficiently accurate clock and piped out through the RS232 interface and a level converter. A few minutes after signals were applied, the "NO GPS" led went off, which I took for a hint that the setup wasn't completely idiotic. Also, pps signals from the RFTG-m-RB and the Odetics, which previously were apart several milliseconds, now followed each other by a 100 or so nanoseconds. Next I flashed a microcontroller board I had lying around, to poll the Odetics receiver for the necessary timing information and send it in Oncore message format to the Lucent module. The pps pulse from the Odetics receiver and a 10 KHz pulse train derived from the 10 MHz "REF OUT" were then observed on a TEK 2440 for several days. While before I applied the gps timing signals to the RFTG-m-RB, the 10 KHz pulses used to advance about 1.6 microseconds per day with respect to the Odetics pps, they now essentially stay where they are, apart for a wander of +/- 2oo nanoseconds during the course of a day. I would like to believe that this is an indication that the rubidium oscillator's frequency is indeed governed by the gps timing information. I'm now waiting for an Oncore UT+ receiver to arrive from China and will repeat the experiment with the original receiver.
On the subject of the Odetics GPStar "time and frequency system", I think I've seen a thread on this list last month where someone had several of them and was about to take them apart. I would like to buy one of those if possible. Also, I might be able to provide a bit of information on the programming interface as well as the the required antenna if someone is interested. Best regards Guido Kueppers _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
