[time-nuts] Lucent RFTG Units

[Robert E. Martinson]

Hope everyone has not stopped experimenting with these nicely made,
reasonably priced, units, but certainly the email regarding them has fallen
to almost zero these last few weeks.

Some help is needed please.

I purchased a pair (RFTG-m-XO & an m-RB, L106A & L105A) and have been
"experimenting with them these last several days.  They both power up, but
both indicate "No GPS", and the XO also indicates "Fault", the RB unit
indicates "ON".  I have the two J5 connectors interconnected per Jim
Miller's email of 12/30/06 at 3:34pm, and the Ref In/Outs with an SMA cable.

Current draw is about 1.1 amps at 24VDC for the pair after warm-up.  The
Motorola Oncore receiver is working fine as I initially tested it while it
was plugged into an old TAPR, TAC-2 pc board and a pc.  It works fine with
TAC32 & Visual GPS.  Even with the receiver plugged back into the XO unit,
the data on the front panel J5-2 is clearly visible with HyperTerminal &
also Visual GPS is happy with this data.  I was using the TAC-2 board to do
the level translating & logic inversion between the XO unit and the PC
serial port.

Even after many hours the RFTG units continue to indicate "No GPS", and the
XO unit also shows "Fault".  I tried the XO unit by itself (no connections
to the RB unit) and the XO is still unable to obtain lock. I have been
monitoring the crystal frequency (using a clip lead directly from the
crystal) of the XO unit for 8 hours with an HP 5370B locked to my HP Z3801A
which appears rock stable per the monitoring program "GPSCon" (it has been
running continuously for several weeks). The frequency is slowly drifting up
(about 30 mHz in 8 hours), thus confirming no GPS lock. The actual frequency
at the moment is about 10 MHz + 60 mHz (i.e. surely within the lock range).

I see commands initially being sent to the GPS receiver (monitoring its
header pin 9 with an oscilloscope), however by simultaneously monitoring the
calculated position using VisualGPS, its obvious that the receiver is not
going into position hold mode.  I only guess that it should.  VisualGPS is
monitoring only, no commands sent to the GPS receiver.

I'm surprised none of us Time-Nuts has been able to obtain any documentation
on these units.  If Lucent is retiring them I see no reason for keeping the
manuals & drawings "classified".  Don't we have any helpful Lucent employees
in the group?



Any help or suggestions on obtaining GPS lock on these units would be much
appreciated.

Regards,
R E Martinson
N1VQR