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

GandalfG8 at aol.com GandalfG8 at aol.com
Fri Oct 24 02:12:38 EDT 2014

Hi Anthony
Many thanks for the photos, makes for a very nice preview.
The GPS module matches photos I have of an Oncore UTplus, but not sure if  
it would also match a straight UT.
Hope you get your fault lights sorted ok, not having a GPS connection might 
 have something to do with that.
In a message dated 24/10/2014 04:50:28 GMT Daylight Time, aroby at antamy.com  

My  curiosity got the better of me so I ordered these earlier this week and 
 received them today.

I've powered both up and quickly measured the  10MHz output.  I don't yet 
have a GPS antenna feed that I can connect, so  couldn't check that out.  And 
I need to look into why both of the units  have the Fault and StdBy lights 
illuminated.  I was surprised how compact  they are and they weight next to 
nothing.  And they are very nicely  made.  I took the tops off both and took 
some photos (see  http://goo.gl/87e8GG), but have not ventured into 
unscrewing everything to get  to the bottom of the boards.  From the top, I didn't 
immediately spot  anything extra on the board for the 10MHz out.  All the 
extras appear to  be for the GPS, but the underside of the boards may tell a 
different  story.


-----Original Message-----
From: time-nuts  [mailto:time-nuts-bounces at febo.com] On Behalf Of Bob 
Sent:  Thursday, October 23, 2014 12:20 PM
To: Discussion of precise time and  frequency measurement
Subject: Re: [time-nuts] Lucent KS-24361,  HP/Symmetricom Z3809A, Z3810A, 
Z3811A, Z3812...

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 pa
d 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 
offering  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 
standby  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 
that  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 

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 substitute.

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 fails.

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:

RFTG          PC

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 un
it.  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 

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  hits.

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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