My electronics flea market SyncServer S200 came with a Furuno GT-8031H GPS module. This module had its GPS week rollover on 2022/09/18. I've modded the S200 with BNC connectors so that it outputs 10MHz and 1PPS. When I connect it to a GPS antenna, the S200 never gets into GPS lock mode: the 10MHz output stays at 9,999,996Hz. I purchased an IL-GPS-0030-B module on AliExpress. These are supposed to have their rollover date in August 2024, though that's not what I'm seeing: it reports a date of sometime 2004, exactly 1024 weeks earlier than today. While I don't strongly care about the date, I care about using the S200 as a GPSDO, though it would still be nice for the date to be correct. With the IL-GPS module, the S200 goes into GPS lock mode, and the 10MHz output frequency is pretty much identical to the one of my TM4313 GPSDO. (It's a bit surprising that the 10MHz of the dirt cheap TM4313 is *slightly* more stable than the S200, but maybe that's probably just a matter of PID control loop parameter choices.) What I'm trying to understand is why the GT-8031H isn't and the IL-GPS is locking when both are reporting an incorrect date. I've already done the following: - soldered probe wires to the 10-pin M12M module connector - confirmed that both module are sending out a 1PPS signal to the S200 motherboard - recorded the 9600 baud RX and TX Motorola binary commands bewteen the motherboard and the modules - wrote a script to decode the recorded request/response traffic to and from the module There are some differences in what the module sends back to the S200, but nothing major jumps out. It's just that after ~20 minutes or so, onces the module reports 7 to 8 satellites, the S200 goes into lock and only then some additional data is sent out by the ILS-GPS. The ultimate goal is to come up with an interposer board that intercepts the GT-8031H data and patches the date. Any ideas? Thanks! Tom