[time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, Z3810A, Z3811A, Z3812A GPSDO system

Anthony Roby aroby at antamy.com
Tue Oct 28 22:52:06 EDT 2014

I played around today with these interfaces and couldn't get anything out of them.  I still don't have my GPS connected, but I would have thought I'd see something out of one of the ports.   I tested the serial port on my PC and that is working, but I don't see anything of note coming off the RFTGs.  I have not connected both together through J5 - maybe that's the next thing to try.  Any particular reason why the -ve side of the RS422 signal is used vs. the +ve?  

I was able also to get SatStat and the RFTG software running on Windows XP under VirtualBox.  Hopefully once I get a signal out of the units, that software will be stable.


-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Stewart Cobb
Sent: Sunday, October 19, 2014 11:53 PM
To: time-nuts at febo.com
Subject: [time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, Z3810A, Z3811A, Z3812A GPSDO system

Once you have applied power, connect the Z3809A cable between the jacks labeled "INTERFACE J5" on each unit.  The earlier RFTG units used a special cable between two DE-9 connectors, and it mattered which end of the cable connected to which unit.  The interconnect for these units is a high-density DE-15 connector (like a VGA plug).  The Z3809A cable is so short that the two units need to be stacked one above the other, or the cable won't reach.  It doesn't seem to matter which end of the cable goes to which unit.  I don't know whether it's a straight-through cable, or whether you could use a VGA cable as a substitute.

When you apply power, all the LEDs on the front panel will flash.  The "NO GPS" light will continue flashing until you connect a GPS antenna.
Once it sees a satellite, the light will stop flashing and remain on.
The unit will conduct a self-survey for several hours.  Eventually, if all is well, the Z3812A ("REF 0" on its front panel) will show one green "ON" light and the Z3811A ("REF 1") will show one yellow "STBY"
light.  This means that the Z3812A is actually transmitting its 15MHz output, and the other one is silently waiting to take over if it fails.

Most time-nuts want to see more than a pretty green light.  The old RFTG series allowed you to hook up a PC to the "RS422/PPS" port and peek under the hood with a diagnostic program.  The program is available on the KO4BB website.  It is written for an old version of Windows, and I had no luck getting it to run under Windows 7.  It does run under WINE (the Windows emulator for Linux) on Ubuntu 12.04 LTS.
To use it, you need to make an adapter cable to connect the oddball
RS-422 pinout to a conventional PC RS-232 pinout.  The adapter cable looks like this:

RFTG          PC

DE-9P         DE-9S

7 <----------> 5

8 <----------> 3

9 <----------> 2

(According to the official specs, this is cheating, because you're connecting the negative side of the differential RS-422 signals to the RS-232, and ignoring the positive side of the differential signals.
However, it's a standard hack, and it's worked every time I've tried

With that adapter, you can see the periodic timetag reports from the unit.  The RFTG program will interpret these timetags when it starts up in "normal mode".  However, when I try to use any of the diagnostic features built into the program, it crashes WINE.  The timetag output was required for compatibility, but I suspect that HP didn't bother to implement the Lucent diagnostics.

Instead, they added a connector which is not on the previous RFTG series.  That connector is labeled, logically enough, "J8-DIAGNOSTIC".
It too is wired with RS-422, so you need to use the same adapter cable as before.  Once you do, you'll find that this connector speaks the usual HP SCPI command set (Hooray!).  I used the official SATSTAT program (again under WINE on 12.04 LTS), but I'm sure that other programs written for this command set will work as well.  The default SATSTAT serial port settings of 9600-8-N-1 worked for me.

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