[time-nuts] New pics of RFTG-m-Rb, and some comparison details

[John Ackermann N8UR]

My RFTG-m-Rb arrived yesterday, so of course it's in pieces on the bench
today.  Photos (along with those of the -XO) are at
http://www.febo.com/time-freq/hardware/Lucent_GPSDO/

In looking at the two units, both use the same main and "mezzanine"
board, but there are component differences.

On the main board, the Rb unit lacks U200 and U202 through U205, but
does have a 10MHz output at the front left corner that's missing on the
XO version.  The programmable device, U104, is identical in both units,
even though the part number includes "XO".  Both units are marked
"104366-001 XO-Ver.02" and have slightly different date codes, both
beginning with 97.  Both boards have the same assembly number, but the
XO board is suffixed -001 and the Rb board is suffixed -002.  Both are
series AA.

On the mezzanine board, U302, a Burr Brown ADS7807U (presumably an ADC,
though I haven't looked it up yet) is present on the XO version, but
missing on the Rb version.  And, programmable device U103 has a
different number.  On the XO version it is "105681-001 03/02 Ver 9.0"
while on the Rb version it is "105089-001 Ver .04 9731".  There's
another programmable device (U202), but it has identical part and
version numbers on both units.

The only other apparent difference between the two versions of the
mezzanine is that the Rb board lacks the mounting hardware and
connectors for installing the GPS, and of course lacks the GPS antenna
connector.  As with the main board, both boards have the same assembly
number but the XO version is suffixed -003 while the Rb version is
suffixed -004.  Both are revision J.

If the Rb isn't being disciplined at all, I'm not sure why they bother
including the mezzanine board, unless it's simply to allow for a PPS
output on the RS-485 connector of the Rb unit (ie, it simply passes
through the PPS from the XO unit).

John