[time-nuts] Upgrading TS2100 from TCXO to OCXO

Joseph M Gwinn gwinn at raytheon.com
Mon Mar 28 13:20:36 UTC 2011

There are some hidden configuration parameters in the TS2100 that vary by 
oscillator type (between TCXO,OCXO, and Rb), and include some control loop 
parameters.  It matters a lot that the firmware uses the correct algorithm 
and parameters.  The Rubidiums are quite far from the crystals, but I 
assume that there is a smaller difference between crystal types.


Robert Watzlavick <rocket at watzlavick.com>
time-nuts at febo.com
03/25/2011 12:39 AM
[time-nuts] Upgrading TS2100 from TCXO to OCXO
Sent by:
time-nuts-bounces at febo.com

I've been able to successfully upgrade my Datum TS2100 to an OCXO from
the stock TCXO.  I didn't see it in the archives so I thought I'd post
my findings.  I noticed that the same firmware was used regardless of
oscillator configuration so there must either be jumpers or a hidden set
of commands.  The newer versions of the ET6000 have jumpers to select
the oscillator but I couldn't find anything similar on the TS2100. 
However, in the back of the manual, 8500-0033 Rev K, Appendix I
describes how to reconfigure the unit to output GPS instead of UTC for
NTP.  I'm not interested in that but there are some hints about a hidden
menu structure (root eng ee) which allows you to change EEPROM
settings.  Here's the hidden menu items:

root eng:
start net interface
timing tools /
serial tools /
eeprom tools /
spi tools /
flash tools /
display tools /
memory tools /
intrinsic help

Going further into one of them, root eng eeprom:
ethernet address
board serial number
gain default
filter constant
low filter constant
set eeprom
get eeprom
read serial eeprom
write serial eeprom
tx 16 bits to eeprom
location for image
info value
intrinsic help

So that's where the default gain and filter constants are set.  You have
to jumper across J4 on the PC board to allow EEPROM writes or you get an
error.  Not sure what the "precision" setting is for (it's currently -19).

I don't have the proper OCXO (yet) but I do have an MV89A OCXO that I
was able to wire into the circuit temporarily.  There is 12V on the
board and the 0.5-4.5V EFC range works well with the MV89A.  I used a
gain of +20 and a filter setting of 0.9994965 based on Jason Rabel's
post from 9/26/2010 (note the sign change on the gain).  The EFC
algorithm had a pretty good overshoot during the first adjustment cycle
and took over an hour to completely settle in but eventually the front
panel Locked LED turned on.  I couldn't find a way to change the
starting value for EFC (d/a) value.

I *think* an Abracon AOCJY1A-10.000MHz-E-SW part will be pin compatible
on the board.  Unfortunately nobody has that one in stock and it's a 10
week lead time so I may end up installing one off-board.  The MV89A is
too tall to fit with the lid on so it's not a long term option.  I
traced out the two SMA pads on the board and they are for the EFC out
and RF in so I could always run them to the back of the unit and put the
OCXO outside the unit.


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