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

[paul swed]

Andrew
Welcome to time-nuts. I really appreciate your detailed write up. I have
seriously considered a used gps emulator a few times. Really don't need
complex solutions. Its more for recovering and working on quite old GPS
receivers and down converters like Austron 2201s. 1990s stuff.
Whats great about the writeup is at least for this unit I can see the
requirements for operation that are far more complex then I would have
expected. I seem to recall there was a series of GPS emulators on ebay that
were priced about right for a hobbyist to consider.
Now at least if some unit shows up I will know what to look out for. Other
wise its a expensive box.
Thanks
Paul
WB8TSL

On Sat, Apr 24, 2021 at 7:02 AM Andrew Kalman <aekalman at gmail.com> wrote:

> 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.
> >
> >
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