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

[David I. Emery]

On Sun, Dec 31, 2006 at 01:15:12AM -0600, Bill Hawkins wrote:
> Ah, well. I have also received two Lucent KS-24019 L106B, aka
> RFTG-m-XO boxes. The serial numbers indicate 95 and 96 construction.
> The assembly numbers, 55761ASSY103902-001 (55761 is the CAGE number
> for Efratom) have Rev E, S/N 522 and Rev H, S/N 2385.

	I have two XOs, a L106B Rev H similar to yours I have apart
around me as I type and a L109 (not yet here and disassembled, but L109
photos are on the net).

	My L106B has a Symmetricom Technical Service label on it and
like yours is a Rev H board with the 023005-1 Efratom OCXO on it.

	The newer units have different part number OCXOs which are
somewhat larger.

> The Efratom crystal(?) oscillators are 023005-001, dated 95 and 96.
> Google has no hits for that part number.

	Yep..

> The GPS receiver has part number 2643686MAB. This gets a few hits
> from vendors that will issue a quote for anything, but will not
> describe the part or its manufacturer.

	I have determined that this almost certainly is a Motorola
Oncore UT (not UT+) receiver with flashable firmware.   I think 6
channels but I haven't dug quite deep enough yet.   I have no clear
notion of what firmware is loaded in the one on my H board yet.   There
probably is a way of reading this out via the serial port stuff.

	The L109 has a UT+ as in my previous message.

	And shoe firmly in mouth, yes I checked - the GPS receivers are
INTERNAL Xtal oscillator versions and appear to be JUST used for the 1
PPS output.   (As for my other shoe, I plan to take apart a 58540A to
see more about what it uses for GPS and whether it derives GPS timing
from the 10 mhz OCXO or an internal GPS crystal oscillator - I knew I
should have grabbed that Thunderbolt when I saw it cheap).

	It appears the mezzanine board has 80C188 firmware dated 03/03
on my H board - same version number as the other people's, however.  
This does imply an upgrade of some type in the 2001-2003 timeframe.   I
have yet to read the PROM, but I suppose it will disassemble nicely...

	Also studying available photos it appears the whole family  is
basically the same design with very few visible differences in the main
board or the mezzanine processor/pll board.   Apparently there are L106A
versions, the L106B (Rev H and J) and a L109 - all obviously the same
design with few variations but made between 1995 and 2002.   They do
seem to have kept up to date with newer Oncore receivers, however.

> I bought these units, and two of their RB cousins, hoping to get
> rid of the HP Z3801 units and the CS standard. They add $30 monthly
> to the electric bill. Now it seems that I was seriously misled, but
> that's the way it goes on the net. I may yet figure out how to
> discipline the RB from the XO.

	Only time will tell whether they have respectable performance. I
was hoping for a couple of GPS disciplined rubidiums for a DSP based
satellite tracking project and may and may not have gotten sent down the
garden path. Looks like I might possibly have found what I need with a
little effort put in.   But I don't see them as Cs replacements.    

> Anybody know how to divide by 2/3rds without a microprocessor? :-)

	The big annoyance is finding a 10 mhz xtal filter to replace the
15 mhz one if one wants to use the output circuitry...  

-- 
   Dave Emery N1PRE,  die at dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in 
celebration of what could have been, but wasn't and is not to be now either."