[time-nuts] Z3805A GPS module going deaf, what modules can replace it?
John Stone
johns at ks.uiuc.edu
Fri Feb 13 14:28:10 EST 2015
Hi,
I've got a Z3805A that I bought off ebay a couple of
years ago, and it recently started going deaf, beginning
with an apparent loss of sensitivity leading to holdovers,
and more recently, receiver errors reported in the system
status.
I have the Z3805A, a thunderbolt, and one of the recently discussed
KS-24361 units sharing the same GPS antenna via a four output
58536A distribution box. I've run the Z3805A on its own
separate antenna and compared its signal levels with the
other units, and it has clearly developed some issue.
After a power cycle, I can get it going by initiating a
survey, but after a day or two of running it will lose
all sats, and in some cases the status command will show
"GPS Rcv: Err".
I queried the hardware info on the GPS in this unit and
from what I've gathered, it's one of the earliest motorola
Oncore GPS receivers based on the "B1121P1114" model number.
What GPS module models can I put into a Z3805A to get it
running again? Any tips are appreciated, including suggestions
for tests I could run on the GPS module, the power supply, or
other items that might be common failure points.
I've included the output from scpi queries below, and the
status from the KS-24361 attached to the same antenna
for comparison:
*IDN?
HEWLETT-PACKARD,Z3805A,3542A00943,3543B-A
:DIAG:LIF:COUN?
+29437
:DIAG:IDEN:GPS?
"COPYRIGHT 1991-1995 MOTOROLA INC.",
"SFTW P/N # 98-P39972M ",
"SOFTWARE VER # 8 ",
"SOFTWARE REV # 4 ",
"SOFTWARE DATE 13 JUL 1995",
"MODEL # B1121P1114 ",
"HDWR P/N # _ ",
"SERIAL # SSG0120281 ",
"MANUFACTUR DATE 5M18 ",
"OPTIONS LIST IB "
Failing Z3805A system status output:
------------------------------- Receiver Status -------------------------------
SYNCHRONIZATION ........................................... [ Outputs Invalid ]
SmartClock Mode ___________________________ Reference Outputs _______________
Locked to TFOM 9 FFOM 3
Recovery 1PPS TI --
Holdover HOLD THR 1.000 us
>> Power-up: GPS acquisition Holdover Uncertainty ____________
Predict --
ACQUISITION .......................................... [ GPS 1PPS CLK Invalid ]
Satellite Status __________________________ Time ____________________________
Tracking: 0 Not Tracking: 0 GPS 08:51:14 [?] 12 Feb 2015
1PPS CLK Absent or freq error
ANT DLY 180 ns
Position ________________________
MODE Survey: 0% complete
Suspended: no track data
INIT LAT N 40:08:01.714
INIT LON W 88:12:27.166
ELEV MASK 10 deg INIT HGT +198.59 m (MSL)
HEALTH MONITOR ...................................................... [ ERROR ]
Self Test: OK Int Pwr: OK Oven Pwr: OK OCXO: OK EFC: OK GPS Rcv: Err
scpi >
For comparison, here is what my recently acquired Z381x / KS-24361 GPSDO
says, driven from the same antenna:
-------------------------- Secondary Receiver Status --------------------------
SYNCHRONIZATION ............................................. [ Outputs Valid ]
SmartClock Mode ___________________________ Reference Outputs _______________
>> Locked to GPS TFOM 3 FFOM 0
Recovery 1PPS TI +10.0 ns relative to GPS
Holdover HOLD THR 1.000 us
Power-up Holdover Uncertainty ____________
Predict 3.7 us/initial 24 hrs
ACQUISITION ................................................ [ GPS 1PPS Valid ]
Tracking: 8 ____ Not Tracking: 2 ________ Time _____ +1 leap second pending
PRN El Az C/N PRN El Az GPS 19:22:10 13 Feb 2015
1 23 302 37 11 15 278 GPS 1PPS Synchronized to GPS Time
4 32 269 43 18 18 138 ANT DLY 60 ns
12 20 49 38 Position ________________________
14 66 30 46 MODE Hold
22 53 146 39
25 36 90 38 LAT N 40:08:00.925
31 61 216 42 LON W 88:12:26.995
32 43 310 46 HGT +200.94 m (GPS)
ELEV MASK 10 deg
HEALTH MONITOR ......................................................... [ OK ]
Self Test: OK Int Pwr: OK Oven Pwr: OK OCXO: OK EFC: OK GPS Rcv: OK
Cheers,
John Stone
--
NIH Center for Macromolecular Modeling and Bioinformatics
Beckman Institute for Advanced Science and Technology
University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801
http://www.ks.uiuc.edu/~johns/ Phone: 217-244-3349
http://www.ks.uiuc.edu/Research/vmd/
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