[time-nuts] Lucent RFTG Units

Wed Jan 31 20:05:34 UTC 2007

Further to my message of 1/30/07 re my RFTG units :

First a correction, the J5-J5 cross-connect info was from Jason Rebel's
email of 12/22/06 at 9:39, not Jim Miller's email.  Thanks Jason!
I had these 2 emails side-by-side at my elbow and picked the header from the
wrong one while typing my email.  Both these emails were VERY useful!

I have most carefully read (& re-read) all the Time-Nuts correspondence on
these RFTG units since mid December.  It has been most helpful.

I assume all have found the Oncore receiver info available by links at:
http://www.tapr.org/gps_oncorevp.html

Rather then reply or comment on the responses received to my request for
info, I have put it all in one, as I assume most Time-Nuts interested in
RFTG's read all the RFTG emails.

Jason:
I have waited well over 12 hours several times and I have tried the XO unit
both connected & disconnected from the RB init, never got a lock.  But
thinking about it, I believe the first time I powered up the XO unit I did
see the "No GPS"  LED blink a couple times.  It's never happened since.
Please post any discoveries you make re these units.  I bet there are other
lurkers (as I was) on this list.

Jim:
Your reverse engineering info was most useful.  Do you have any additional
info that might be useful to me?
Thanks for the warning about loading or disturbing the various internal
connections, a good point!  I have tried to get it to lock with no external
wires or probes.
The 5VDC is good on the antenna connector, and the receiver/antenna is
working fine, many satellites tracked, and VisualGPS operates normally when
connected to J5-2 via a level inverter/converter (a TAC-2) .  TAC32 displays
normally also after a short delay because of course it doesn't get the
Motorola initiation messages it expects to receive.  How do you connect
TAC32 to your XO receiver?   I can see commands going to the GPS receiver on
an oscilloscope at the receiver's header pin-9.  How would you suggest I
capture them?  Can Hyperterminal do it via a level converter and maybe an
inverter? OR??   Note the GPS receiver's transmitted data is inverted per
the TAC-2 circuits & documentation.

Phil Staton:
By all means please post your notes re what you did to get your XO unit to
lock-up.  I'm near out of ideas with mine.

David I. Emery:
My units are L106A  and L105A, dates of manufacturer 9828 & 9825 (yymm)
respectively.  Have you managed to get your units to lock-up??  Any secrets?
I'm in Waltham so an eyeball QSO would be possible.  You are invited to
attend the WARA64 (Waltham amateur radio group)  monthly meeting tonight
(Wednesday) at 7 pm in the Waltham Public Library, Trustees Room, on Main
street.  The meeting is not related to time-nuts stuff.

Regards,
Bob Martinson, N1VQR
Waltham, MA

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Robert E. Martinson
Sent: Tuesday, January 30, 2007 1:22 PM
To: time-nuts at febo.com
Subject: [time-nuts] Lucent RFTG Units

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

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