[time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, Z3810A, Z3811A, Z3812...

GandalfG8 at aol.com GandalfG8 at aol.com
Thu Oct 23 15:01:02 EDT 2014

Hi Bob
Many thanks for the feedback, that's very useful.
I had assumed from the photos of the two units that a degree of surgery  
would be required to bring out the 10MHz on the REF-1, if only because the 
10MHz  and GPS connectors currently use the same hole in the panel.
I had also wondered if one of the connectors might already use a  flying 
lead, not having considered that they might use a shared space in quite  in 
the way you describe, but that obviously makes sense if the two are  never 
intended to co-exist and I understand better now.
I've so far had to rely on the auction photos for any hint as  to what's 
inside the boxes, which does make for a rather limited  view:-)
I don't know how closely the interconnecting cable will match that for  the 
RFTG-m, that one uses 9 pin connectors so may be a bit more restricted  but 
I would have expected them to be similar at least.
If you haven't already got them, there's some RFTG-m manuals and files  
available on Didier's manual site, including one with details of the  
interconnecting cable.
Obviously those best placed to consider any conversion between units would  
be those with one of each available as samples, so there's one downside to  
buying two the same after all:-)
In a message dated 23/10/2014 18:23:24 GMT Daylight Time, bob at evoria.net  

My units  came in today.  What I got appears to be new-in-box.  It's 
probably  the only thing I'll ever get with a blue Agilent sticker on the box.   
=)  It has a yellow Symmetricom notice inside the box.
The circuit  board appears to be the same on both units, but that says 
nothing about the  firmware, of course.  The REF-1 has an Oncore receiver 
labeled TM-AB -  whichever one that is, small parts to support it, and a TNC 
connector for the  GPS receiver.

The REF-0  is missing everything related to the  receiver, and has an SMA 
for the 10MHz output in the space where the REF-1 has  the TNC along with a 
few extra small parts.  This is a shared space with  both SMA and TNC pads, 
though they don't seem to share the same electrical  path.  Since the SMA and 
TNC share the same physical space, even if the  10MHz is available 
somewhere, you'd have to do some surgery on the case before  you could bring it out. 
 Probably by adding a hole in the case for the  GPS antenna and using the 
pad space for the SMA.

It will be a day or  two before I have the bits to apply power and connect 
an antenna.  So,  that's what I know.  I'd probably just break something if 
I tried to find  and bring out the 10MHz, so I'll have to leave that to 
someone else.   But, the appropriate signals need to get between the boards, so 
I wonder  what's on the Interface pins?  Maybe just arbitration, 1PPS, and 
sawtooth  comms?
In my case, I do need the 10MHz, so I'm just as happy to have bought  both 
units at this point.  Maybe, down the road, someone will come up  with the 
mods to convert a REF-1 into a REF-0, and vice versa, unless the  firmware 
prevents that.

From: GandalfG8---  via time-nuts <time-nuts at febo.com>
To: time-nuts at febo.com 
Sent:  Tuesday, October 21, 2014 5:59 AM
Subject: Re: [time-nuts] Lucent KS-24361,  HP/Symmetricom Z3809A, Z3810A, 
Z3811A, Z3812...

It seems  from the auction revision table that this seller has been 
these  for some time, so perhaps another "hidden" gem:-), but it's  perhaps 
also worth noting that if this system functions on similar principles  to  
earlier RFTG kit then the GPS conditioning is only applied to the  unit 
actually  containing the GPS module, with the other unit  intended as  a 
should the first one fail.

In other  words, unless the system redundancy is really required most users 
would probably only need the GPS based unit, or would at least be   better 
off buying two of those for the same money that the "matched"  pair  would 

The only advantage, as far as I'm aware  anyway, of the non-GPS unit is 
it contains a 10MHz  output.
However, Skip Withrow published modification details in January  2013  
showing how straightforward it was to add the the 10MHz output,  to the  
RFTGm-II-XO module, the PCB location for the socket was  already available, 
so I  
would suspect it wouldn't be too difficult  on these either.



In a message  dated 20/10/2014 05:53:29 GMT Daylight Time,  
stewart.cobb at gmail.com  writes:

Fellow  time-nuts,

This (long) post is a review of  the HP/Symmetricom Z3810A  (or Z3810AS)
GPSDO system built for Lucent  circa 2000.  I wrote it  because I looked
for more information  before I bought one, and couldn't  find much.
It's relevant because  (as of this writing), you can buy a full  system
on the usual auction  site for about $150 plus shipping.  For  those of
you lamenting  the dearth of cheap Thunderbolts, this looks like  one of
the best  deals going.  The description of these objects does  not
include  "GPSDO", so time-nuts may have missed it.  Search for one  of
the  part numbers in the subject line and you should find it.

So  what  is it?  It's a dual GPSDO built by HP as a reference
(Redundant   Frequency and Time Generator, or RFTG) for a Lucent
cell-phone base   station, built to Lucent's spec KS-24361. Internally,
it's a close  cousin  of a later-model Z3805A.  Externally, it looks to
be  almost a drop-in  replacement for the earlier RFTG system built  to
Lucent's spec  KS-24019.  That was a redundant system  containing one
rubidium (LPRO,  in the one I have) and one OCXO in  two
almost-identical boxes.  That  spec went through several  revisions with
slightly different nameplates and  presumably slightly  different
internals.  You can generally find one  or two examples  on the auction
site (search for RFTG or  KS-24019).

This system  is similar, but the two boxes each contain a  Milliren
(MTI)  260-0624-C 5.000MHz DOCXO, and neither contains a  rubidium.   The
Milliren DOXCO is the same one used in the later models  of the  HP
Z3805A / 58503A.  It's a very high-performance DOCXO, in the   same
class as the legendary HP 10811, and better than the one in   most
surplus Thunderbolts.  The 5 MHz output is multiplied up to  10  MHz in
at least one unit, and 15 MHz in both units.  I don't  have the  ability
to measure phase noise on these outputs, but I'd be  interested to  see
the results if someone  could.

Nomenclature:  The Z3810AS  (there always seems to be  an "S" at the
end) is a system consisting of the  Z3811A (the unit  containing a GPS
receiver), the Z3812A (the unit with no  GPS  receiver), and the Z3809A
(a stupid little interconnect cable).  The  GPS receiver inside the
Z3811A is a Motorola device, presumably some   version of an OnCore.
Where the Z3811A has a TNC GPS antenna input,  the  Z3812A has an SMA
connector labeled "10MHz TP".  That is  indeed a 10  MHz output.  It
comes active as soon as power is  applied to the unit,  and its
frequency follows the warmup curve of  the OCXO.  The two units  have
identical PCBs (stuffed slightly  differently), and I have no  doubt
that someone can figure out how to  add a 10 MHz output to the  Z3811A
as well.

Operation:   From the outside, these units are  broadly similar to
earlier units in  the Lucent RFTG series. The (extremely  valuable)
website run by  Didier, KO4BB, has a lot of information on  those
earlier units, much  of which still applies here.  The purpose of  these
units was to  provide a reliable source of frequency and  timing
information to the  cell-site electronics.  The 15 MHz outputs  from
both units were  connected to a power combiner/splitter and directed  to
various parts  of the transmitter.  The units negotiate with each  other
so that  only one 15 MHz output is active at a time.  The  outputs
labeled  "RS422/1PPS" contained a 4800 baud (?) serial time code  as
well as  the PPS signal, which were sent to the control  computer.

Power is  applied to the connector labeled "+24VDC" and "P1",  in
exactly the  same way as the earlier RFTG units. Apply +24V to pin  1
and the other  side of the power supply (GND or RTN) to pin 2.  In
these units, that  power supply goes directly to an isolated  Lucent
DC/DC converter  brick labeled "IN: DC 18-36, 1.9A".  Presumably  you
can run both  units with a 4-amp supply.

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

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

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:


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.

After about 24 hours, with a poorly-sited indoor GPS  antenna,  my
system has converged to TFOM=3, FFOM=0 (the best  possible  numbers),
and a "predicted 24-hour holdover uncertainty" of  5.2  microseconds,
which is not too shabby.  It found the correct  day and  year without
any assistance, so if it has a "GPS week number  rollover"  problem,
it's still in the future.  I don't currently  have the ability  to
compare the 10 MHz output to anything else.   Again, if someone  else
can, I'd be interested to see the  results.

Additional Notes:  The parts on the boards all have date  codes of 1998
or 1999.  The  Motorola GPS receiver has a firmware  label that reads
"02/04/00".  The  SCPI error logs inside the HP  units were virgin when
I first got  them.  They had 84 and 94  power cycles, respectively.
Before the GPS  receiver acquired time,  the error log timestamps read
"2000-05-09  00:00:00", which I  interpret as a firmware release date.

The PCB has an  interesting  feature.  Next to each soldered-in pin of
the Milliren  OCXO is a  single-pin socket soldered into the board.  I'm
guessing  this  was used in manufacturing, to temporarily install a
Milliren and   confirm that the system worked before permanently
soldering it in.   (At production prices, the Milliren would have cost
far more than the  rest  of the PCB.)  You might be able to use this in
reverse, if  you have a  set of Millirens to test from another source.

The  Z3809A interconnect  cable has three of the 15 pins on each  end
clipped a bit shorter than the  rest.  Not so short that they  won't
eventually make contact, but short  enough to make contact later  than
the rest.  Don't know why, but it's  clearly  deliberate.  A lot of
hot-plug connectors are built that way,   including USB connectors.  I
have no idea what the pinout of the   interconnect is.

The redundant system slaves both DOCXOs to the  same  GPS reference.
Inside the GPS loop bandwidth, the two  oscillators will have  almost
the same frequency and will differ only  by phase noise and  short-term
stability.  This is almost a  perfect setup for  experimenting with
certain kinds of time-nut  measurements, assuming someone  can figure
out how to get 10MHz out of  the Z3811A unit.  If you then  command both
units into holdover,  you could measure longer-term stability  as well.

The units are  described as "new in factory sealed box".  After an
archeological  investigation of the various strata of labels and  tape
on the boxes,  I would say that's probably accurate.  My set seems  to
have been  shipped from the Agilent factory in Korea to Symmetricom   in
Sunnyvale, CA sometime in August, 2000, shortly after it was   built,
and remained untouched until I opened it.  I'm guessing it  was  built
and saved as part of a spares program for Lucent, and  kept  until
Lucent decided they didn't need spares any more.

I  have no  connection with the current seller of these units (or  any
other sellers,  for that matter) except as a satisfied  customer.  I
think I'll order  another set as a spare, before the  feeding frenzy

Request for  help:  Both the SatStat  and RFTG programs run under WINE
on stock  Ubuntu 12.04 LTS (32-bit)  without any tricks or  special
configuration.  Neither seems to  run under WINE on Ubuntu  14.04 LTS
(64-bit). I am a WINE  novice.  Any hints from WINE experts  would be
appreciated.   Also, I've been able to run TimeLab under WINE,  but I
can't connect  it to my USB-to-488 interface, so I can't take  data.  If
anyone  can tell me how to set that up, I'd be extremely   grateful.

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