[time-nuts] Lucent RFTG Units

Brooke Clarke brooke at pacific.net
Wed Jan 31 15:37:20 EST 2007


Hi Robert:

A few general comments.
1) Many GPS receivers monitor the antenna DC current.  If it's too high 
or too low they assume there's a problem with the antenna.  On the 
Trimble Trimpack receivers I rigged a "T" connector with a shunt 
resistor and a DC block to fool the receiver.

2) The Trimpack receivers need a high gain antenna (about 41 dB), but 
most GPS receivers look for more like 20 dB and some expect no antenna 
gain.  It may be that a given receiver will not work if the wrong 
antenna gain is used.

http://www.pacificsites.com/~brooke/Trimpack.shtml#Ant

3) The data to/from the Motorola GPS modules could be tapped by using a 
MAX232 type IC driving a PC running hyperterminal.  There is the TTL  
data going to the receiver and TTL data coming from the receiver.  I 
expect that the MAX232 TTL input would not load the existing data 
lines.  You may want to record the data starting with your unit powered 
off and for some time after turning the power on.

Just some thoughts & Have Fun,

Brooke Clarke

w/Java http://www.PRC68.com
w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
http://www.precisionclock.com



Robert E. Martinson wrote:

>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
>
>_______________________________________________
>time-nuts mailing list
>time-nuts at febo.com
>https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>
>_______________________________________________
>time-nuts mailing list
>time-nuts at febo.com
>https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>
>  
>



More information about the time-nuts mailing list