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

[Bob kb8tq]

Hi

The last time I recall this coming up, we were going after the single channel 
versions of these boxes. They are fine for doing a calibrated sensitivity test.
They aren’t great for a full checkout of a receiver. For what little they cost
(at least back then) not a bad deal.

Bob

> On Apr 24, 2021, at 12:14 PM, paul swed <paulswedb at gmail.com> wrote:
> 
> 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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