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| TM4313 GPSDO: strange behavior after a night of poor reception |
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| shapirus:
--- Quote from: shapirus on April 10, 2024, 09:16:14 am ---The next thing to test is to bring the antenna, without disconnecting it, further into inside of the room to simulate a signal level degradation. --- End quote --- This test is passed too. 1) antenna moved deep indoors: --- Code: ---Ph = -16, D = 552276, GL = 0, LOS = 3, ST = 552, AF = 37, RT = 2005 Ph = -15, D = 552269, GL = 0, LOS = 3, ST = 553, AF = 37, RT = 2006 Ph = -15, D = 552263, GL = 0, LOS = 3, ST = 554, AF = 37, RT = 2007 Ph = -15, D = 552256, GL = 0, LOS = 3, ST = 555, AF = 37, RT = 2008 Ph = -14, D = 552254, GL = 0, LOS = 3, ST = 556, AF = 37, RT = 2009 Ph = -14, D = 552247, GL = 1, LOS = 3, ST = 557, AF = 37, RT = 2010 Ph = -14, D = 552247, GL = 1, LOS = 4, ST = 0, AF = 37, sK = 0.00000, RT = 2011 Ph = -14, D = 551097, GL = 1, LOS = 4, ST = 1, AF = 37, RT = 2012 Ph = -14, D = 551097, GL = 1, LOS = 4, ST = 2, AF = 37, RT = 2013 Ph = -14, D = 551097, GL = 1, LOS = 4, ST = 3, AF = 37, RT = 2014 Ph = -14, D = 551097, GL = 1, LOS = 4, ST = 4, AF = 37, RT = 2015 Ph = -14, D = 551097, GL = 1, LOS = 4, ST = 5, AF = 37, RT = 2016 Ph = -14, D = 551097, GL = 1, LOS = 4, ST = 6, AF = 37, RT = 2017 Ph = -14, D = 551097, GL = 1, LOS = 4, ST = 7, AF = 37, RT = 2018 --- End code --- 2) antenna brought back to the window: --- Code: ---Ph = -14, D = 551097, GL = 1, LOS = 4, ST = 156, AF = 37, RT = 2167 Ph = -14, D = 551097, GL = 1, LOS = 4, ST = 157, AF = 37, RT = 2168 Ph = -14, D = 551097, GL = 1, LOS = 4, ST = 158, AF = 37, RT = 2169 Ph = -14, D = 551097, GL = 1, LOS = 4, ST = 159, AF = 37, RT = 2170 Ph = 0, D = 551097, GL = 1, LOS = 4, ST = 160, AF = 37, RT = 2171 Ph = 0, D = 551097, GL = 1, LOS = 4, ST = 161, AF = 37, RT = 2172 Ph = 0, D = 551097, GL = 1, LOS = 4, ST = 162, AF = 37, RT = 2173 Ph = 0, D = 551097, GL = 1, LOS = 4, ST = 163, AF = 37, RT = 2174 Ph = -1, D = 551097, GL = 1, LOS = 4, ST = 164, AF = 37, RT = 2175 Ph = 1, D = 551097, GL = 1, LOS = 4, ST = 165, AF = 37, RT = 2176 Ph = 3, D = 551097, GL = 1, LOS = 4, ST = 166, AF = 37, RT = 2177 Ph = 4, D = 551097, GL = 1, LOS = 4, ST = 167, AF = 37, RT = 2178 Ph = 5, D = 551097, GL = 0, LOS = 4, ST = 168, AF = 37, RT = 2179 Ph = 0, D = 551097, GL = 0, LOS = 3, ST = 0, AF = 37, RT = 2180 Ph = 2, D = 551097, GL = 0, LOS = 3, ST = 1, AF = 37, RT = 2181 Ph = 3, D = 551097, GL = 0, LOS = 3, ST = 2, AF = 37, RT = 2182 Ph = 5, D = 551097, GL = 0, LOS = 3, ST = 3, AF = 37, RT = 2183 Ph = 6, D = 551097, GL = 0, LOS = 3, ST = 4, AF = 37, RT = 2184 Ph = 7, D = 550771, GL = 0, LOS = 3, ST = 5, AF = 37, RT = 2185 Ph = 10, D = 550656, GL = 0, LOS = 3, ST = 6, AF = 37, RT = 2186 --- End code --- The output frequency remained stable during the entire length of this test. So, I guess, no night-time frequency reference for me, for now :). At least without an outdoors antenna. Yes it would be interesting to test how other GPSDO behave in this scenario, but the level of this curiosity is not high enough to justify the expense required to get another unit. |
| shapirus:
I took it apart to change the jumpers to connect to the GPS module's serial port and took some pictures while I was there. OCXO: Date and HW revision: The 1 PPS output is connected like so (i.e., not to the GPS module): |
| Zenith:
--- Quote from: tverbeure on April 09, 2024, 05:21:59 pm ---There's very little literature on the TM4313 other than my blog post, and other than you and me, I don't think anyone has gone father in their analysis of the TM4313 log messages. --- End quote --- I'm glad this thread has appeared. I've had a TM4313 for about three years. It came with no instructions and until now I couldn't find anything about it on the WWW, although I hadn't looked for some time. It sits there with the antenna on a window sill, not outside, and agrees with a Racal 1992 with the better OCXO (04E) option, to within a few ppb over the course of a week. I'd always wanted to explore its data reporting features. It's lost lock a couple of times when the antenna has been covered up with something or other. I assume that for practical purposes, calibrating synthesised sig gens and adjusting frequency counters with ancient OCXOs, (so no better than 1 part in 10^8) that the TM4313 is perfect. One thing that has surprised me is how good the AliExpress ex-equipment CTI OCXOs are. |
| tverbeure:
--- Quote from: shapirus on April 10, 2024, 10:02:51 am ---The 1 PPS output is connected like so (i.e., not to the GPS module): --- End quote --- Yeah, that’s expected. The 1PPS coming out of the GPS module is way too jittery. |
| shapirus:
Update. I cannot reproduce this lock-up when the jumpers are set to receive messages from the GPS module! Yesterday in the evening it was running with the jumpers set for the MCU's UART output. The GPSDO locked up as described in first post. I disconnected and reconnected the antenna, it started tracking, but then went into that unstable state again. Then I changed the jumpers and let it run again. Guess what, no issues. It's tracking just fine. Yes it did lose tracking a couple of times at some point, but then resumed it properly. Right now, and it was a second (non-consecutive though) night with no lock-up issues, it's generating a good output frequency with no "seeking" oscillation. I wonder what do the jumpers have to do with it and how could it affect things. At this point it does not look like a coincidence. |
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