[time-nuts] Re: 20210423: Introduction and Request for Spirent GSS4200 User Manual / Help

[Andrew Kalman]

So, an update. I was graciously provided with the User Manual for the
GSS4200 (thank you!). Having read through it and having played with my
GSS4200, I conclude the following:

   - My unit is functionally working (well) -- 10MHz clock was not far off,
   output levels are correct, etc., it is generating a signal where one should
   be.
   - Most of the "commanded" behavior I had been observing (using the
   GSS6100 user manual as a guide, issuing commands over GPIB) was the
   behavior of the unit when operating in GSS6100 emulation mode (single
   channel, ability to change the SVID, maybe the ability to change the week,
   etc.).
   - This GSS4200 has (sadly) only one scenario loaded in its NVM memory --
   "4200calibration" that is 10 minutes long. It basically outputs a
   single-channel signal on PRN 1, makes sense for calibration.
   - Based on my reading of the manual, at a minimum, if you have access to
   the utilities CD ROM, you can load scenario "libraries" (#sats, signal
   strengths, ground trajectories, etc.) and then run them (in a looping mode,
   if you want) on this unit. A combination of utilities (that work only over
   USB) load scenarios into the GSS4200.
   - Each scenario also includes the appropriate ephemeris and almanac info
   (provided by Spirent).
   - Scenarios must be under 5 minutes long.Dunno how the 4200calibration
   scenario is 600s long ...
   - The scenario and other file formats are not / not well documented.
   Spirent had a server that you would provide scenario requests to, and I'm
   guessing that it would generate the scenario file along with the
   accompanying ephemeris and almanac info, and crunch that all into a .scb
   scenario file. You can then use a provided utility to combine multiple
   scenarios into a scenario library that you can then load into the GSS4200.
   Note that there is no obvious way for a user to ** generate **  their own
   scenarios (or ephemeris or almanac).
   - GSS6100 emulation is "independent" of GSS4200 scenario operation. For
   example, the GSS4200 manual does not mention an explicit level command
   (that is part of the GSS6100's command set), yet the example scenarios
   alter the output level, so clearly the unit can do that.
   - So, the intended way to use this unit appears to be:
      - Obtain supplied/default scenarios (*.scb) or ones built for you via
      the Spirent web interface
      - Optionally combine them into libraries (*.scl) via the Scenario
      Selection Tool
      - Download them into the GSS4200 (max 512KB worth) using the Flash
      Loader Utility
      - Run the scenario via RUNS <x> for one run, or LOOP <x> for looping,
      where <x> is the scenario number.


   - So, I'm kinda stuck here. I want the GSS4200 available for a quick and
   consistent validation of the proper operation of GPS receivers. For that,
   at a minimum, I need some complete scenarios (the default ones supplied
   with the unit would be alright) that I can load into the unit to run in
   looping mode. There are 18 default scenarios, 3 each (different power
   levels, stationary vs. moving, etc.) for six cities: Boston, LA, Tokyo,
   Hanover, Seoul and Shanghai.They all run at various dates in 2003,
   suggesting that the GSS4200 was released around that time.
   - My unit only has the one calibration scenario (PRN 1 only, standard
   output level) loaded ... I'm not really clear on the usefulness of a single
   channel of GPS signal.
   - This unit differs from more modern units like Spectracom/Orolia GSG
   series units in that the newer units allow you to generate your own
   scenarios, and they pull ephemeris and almanac data directly from the
   internet. Plus more channels and constellations, more interference and
   other simulations, etc.

So, I conclude that without the full GSS4200 utilities disk, I'm kinda
stuck. :-(

--Andrew

--------------------------------
Andrew E. Kalman, Ph.D.


On Fri, Apr 23, 2021 at 1:15 PM Andrew Kalman <aek at pumpkininc.com> wrote:

> Hello.
>
> [SNIP]
>
> I am ** desperate ** for a User Manual for the Spirent GSS4200 GNSS
> simulator (e.g.,
> https://www.testequipmentconnection.com/54837/Spirent_GSS4200.php). That
> model is somewhat unique, in that it's one of only a very few that Spirent
> released that can/will run without an external "control" program. Using the
> manual from the GSS6100, I'm able to do a couple of things with the GSS4200
> over GPIB, but for the life of me I cannot figure out how to get the
> GSS4200 into a mode other than single-channel (it supports 6 channels, and
> has a single-channel mode). I suspect there is a command to do this, but I
> have not been able to figure it out.
>
> I have spent 8+ hours searching sites and archives, to no avail. Spirent
> has done a rather impressive job of locking down their support software and
> docs behind a paywall (and I wonder if they even have the docs for the
> GSS4200 any more). Any help is appreciated, I'm happy to give back if
> someone wants to snag another GSS4200 (around $700 used) and use it as a
> simulator.
>
>