[time-nuts] Lucent KS-24361 GPSDO arrived today several questions

GandalfG8 at aol.com GandalfG8 at aol.com
Fri Nov 7 04:03:01 EST 2014

Hi Bob
Very many thanks for the prod re the Diagnostic port.
Considering the other GPS kit I talk to using Hyperterminal and the  like, 
often because there's no other option, I don't know why it's  never occurred 
to me to do the same with the Z3801As and now  these......
and any rude suggestions as to why will just be politely  ignored:-)
It's not that I don't have access to the command set, but  I suspect that 
twelve years or so ago, totally green when it came to  GPSDOs and with my 
first Z3801A to play with, I was just grateful to find  SatStat, and eventually 
some nice commercial options, and never gave it a  thought after that, 
silly me.
Anyway, I've just switched my Z3811A comms over to Hyperterminal  and tried 
the :SYST:STAT? command for starters.
That's obviously what SatStat uses to generate it's front page, although it 
 is continuously updated with SatStat, and we do have contact, and 
something  else to play with:-)
In a message dated 07/11/2014 00:07:56 GMT Standard Time, kb8tq at n1k.org  


Ok, I got to spend a little quality time with my pair  today. I mostly 
poked at the Diag port with a terminal program. 

Both  of the units seem talk over the Diag port regardless of the mode they 
are in  (master / slave / fault ). Both respond to a sub-set of the Z3801 
SCPI  commands (= not all commands work). There are a few enhancements where 
a query  to a “node” gives a reply (which it should not if it’s “node only”
). All of it  works ok at 9600 baud 8N1. All of it comes back with an error 
message (E-xxx)  after a valid command response. It may not like the 
terminal program sending  cr/lf or something like that. 

By far the most useful thing to type is  :SYST:STAT? 
That executes the system:status request and gives you a nice  full screen 
of information. It shows you about 95% of the useful information  all on one 
page. About the only major thing missing is the DAC value. That’s  available 
with another command out of the Z3801 list. It does take a while to  
compose and transmit the screen, so it’s not the best way to to this forever  and 

The data from the request is the same on both boxes. Same  everything 
except one shows as standby etc. The interesting details are things  like 
elevation mask and cable delay. Why interesting? You can set them with  discrete 
commands. You can also query the data with the same commands to make  sure the 
box “took” what you sent. 

This allows experimentation with  changing the elevation mask on each box 
(or just simply doing a discrete query  for the mask on each box). The Ref-0 
/ slave will happily change things around  with discrete commands. None of 
them are reflected in the :SYST:STAT? listing  on the Ref-0 or Ref-1. When 
you look at the Ref-1 / gps box, it’s discrete  query information matches the 
:SYST:STAT? screen on both boxes. When you  change things on the Ref-1 box 
both screens follow that data.  


When you pull the antenna on the gps box, it immediately  (almost) goes 
into gps fault led flashing mode. The slave box happily sits  there for a while 
(say a minute) with it’s gps led saying all is well. When  you plug the 
antenna back in, the process is reversed. The gps box goes out of  flash mode 
right away. The led goes out in a bit. The led on the slave box  does not 
follow for a minute or so. 


All of this suggests  to me that the Ref-0 / slave does not talk back to 
the other box via serial.  It also suggests to me that all it “sees” from the 
Ref-1/gps box are the  duplicates of the serial string out of the Motorola 
gps module. The Ref-0 just  figures out what’s happening by watching those 
strings as they roll  by.

Hope that makes sense….


If that’s all true, it  should be “easy” to put dummy gps sentences into 
the Ref-0 interface port and  a pps from something else. Once it sees stuff 
that it likes, it will start  locking up to that pps. Cheap micro and just 
about any modern gps = fancy new  GPSDO. Quick / easy / not much work. A 
little more complex if you decide to  translate sawtooth data. That of course 
assumes these boxes do anything with  sawtooth ...


> On Nov 6, 2014, at 7:52 AM,  GandalfG8--- via time-nuts 
<time-nuts at febo.com> wrote:
>  Hi Bob
> I view the master/slave situation the same way you do,  but only  
> because Lucent effectively sets things up  the other way round so just  
> wanted to be sure which way Paul  was considering it.
> As regards, the "faking", yes, a single  15 way plug containing just  a 
> and a resistor is exactly  what I use now.
> I realise the RS422 fudge isn't ideal but  certainly very handy for some  
> quick tests.
>  I've got two or three RS422 PCI interfaces but hadn't previously had any 
> spare slots, now I've got a couple of lovely Magma 13 way PCI  expansion 
> but need to hack them about so the ports are at the  front.
> Whoever decided rack mount PC kit should be built with all  the  
> at the rear must have been really nuts, and it  was too long ago  to use 
> "corridors" of racks as a viable  excuse, someone somewhere just fitted  
ears to 
> desk top style  cases and left the rest of us to get on with  it..
> One  of the best things I ever did was to buy a pair of "back to front"   
> rackmount PC cases with all ports and cards available at the front,  
trouble is  
> now I want everything else to match, and most test  gear has just the 
> issues!
> All good fun,  and certainly never a dull moment:-)
> Regards
>  Nigel

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