[time-nuts] Lucent RFTGM-II-Rb (KS-24019 L108) Standalone

Sat Nov 24 03:23:54 UTC 2018

Lucent RFTGm-II-Rb (KS-24019 L108) Standalone Notes

After further investigation, I found that the pinout in the ‘Lucent RFTGm-II-XO Notes’ pdf from John Warner @ Warner Labs is correct. And after sifting through lots of messages and archives, I found one message from Guido Kueppers from 11 Feb 2011 that was basically right on but addressed the RFTG-m-Rb model. <https://lists.febo.com/pipermail/time-nuts_lists.febo.com/2011-February/036741.html> The same information would appear to apply to the RFTGm-II-Rb as well.

To reiterate: the normal connections between the Rb and XO are:

Rb					Xo
1 -  Amplitude Det.—>  - 5 Normally HIGH
2 -  Unused/W202-A     - 4
3 -  Rb Alarm —>       - 3 Normally about 3.3v
4 -  <— GPS Data Rx    - 2 (TTL level, idle HIGH) Goes to W202-B in Rb
5 -  N/C Unused?       - 1 Normally LOW
6 -  Unused/W203-A     - 9
7 -  PPS Out from Rb   - 8 (400us, TTL level, idle LOW)
8 -  PPS In (from XO)  - 7 ‘REF’ in RFTGM software phase error display 
9 -  PPS In from GPS   - 6 (200ms, TTL level, idle LOW) Goes to W203-B in Rb

The quick summary is that you simply need to connect pin 4 directly to a Motorola Oncore receiver outputting @@Ea messages each second (binary mode), and the Oncore PPS output directly to pin 9. I also jumpered pin 9 to pin 8, the REF PPS input. My testing was done using an Oncore GT+. It does not appear to be necessary to use the UT+.

Additional notes:
-) Unlike the KS-24361, no messages besides the @@Ea need to be sent by the GPS.
-) TRAIM does not appear to be required.
-) There is no need for inverters on any signal lines.
-) Putting my Oncore in position hold mode changes the tracked satellites to 1, causing a ‘No GPS’ error. Just leave it in 3D mode.
-) After the first continuous run over night, the unit made a frequency adjustment. It was a large enough step to cause a fault. A soft reset was done and the unit then operated normally.
-) The @@Ea message update rate can be as long as 8 seconds before triggering a ‘No GPS’ error. No known benefit to making it > 1 second.
-) In the RFTGM software, the password to the EPR Rb control menu is ‘ALICE’, the password to the EPR XO control menu is ‘ALICE2’

The BEST part of this is that the Oncore connector footprint on the daughterboard of the RFTGm-II-Rb is connected to the proper pins of the interface port. If you use an Oncore with the onboard Lithium battery and preconfigure it out of idle mode with @@Ea01, you can drop it in and it will just work. There is some fiddling with the antenna port (and you COULD populate the missing parts on the RFTG daughterboard I guess) but that’s not much of a barrier.

There may be a screenshot of RFTGM software showing normal disciplined operation:

> On Nov 21, 2018, at 2:16 AM, ziggy9+time-nuts at pumpkinbrook.com wrote:
> 
> To help keep me occupied over the holidays, I’ve dusted off a Lucent RFTGm-II-Rb unit to see if I can make it behave as a standalone device. It would be easier with the mating L109 XO unit, but unfortunately I don’t have one. I’ve done quite a bit of digging over the last week or so but have been unable to find out the details of the ‘Interface’ port with any certainty. Most importantly, which pin the the GPS messages are received on and what are the PPS/data signal levels/polarity- I’d prefer not to do any damage applying RS232 levels for example. I have searched the list archives and while I found info on the KS-24361, not so much on the KS-24019. 
> 
> The work done by Dan Watson and others on the KS-24361 is useful, but the ports are different (these units have DB-9 while the KS-24361 has DB-15). The same approach is probably valid but the details are different. And if someone has a L109 XO unit they would like to part with, please let me know.
> 
> 
> 
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