LOG OF ADJUSTMENTS TO SIGMA TAU MASER AT GREEN BANK Model NAV-2001, serial # 105-17 (INTERFEROMETER CONTROL BUILDING.) Maser moved to Reber Lab: GBT equipment room, Oct 29, 1998. ------------------------------------------------------------- Note: also logs of other changes at the timing center. ------------------------------------------------------------- Date Changed Synthesizer** 1PPS delay new ST-GPS Remarks ----------------- --------------- ------------ ------------ ------------------ pre-July23, 1992 31045259 ? July 23, 1992 31037403 925257 -0.20 us 1pps counter power off. Sep 20, 1993 1230UT " 028424 Dec 3, 1993 31034000 028426 Dec 16, 1993 31030000 " Jan 6, 1994 31025000 " Jan 31, 1994 " 028427 +0.39 us May 03, 1994 31023000 028428 +0.20 us May 19, 1994 " 404062 +0.80 us Batteries replaced. Aug 08, 1994 2020UT " 935840 +0.52 us Power off to 1PPS counter. Aug 09, 1994 1330UT 31016200 " Oct 13, 1994 1330UT (867,210,162,00) " Offset 10-8 ## Oct 14, 1994 1730UT (869,310,162,00) 934859 +0.11 us restore to original state. Dec 09, 1994 4-16 UT " " +1.5 us Cavity register adjust. #3 Feb 22, 1995 1843UT (867,210,162,00) " Offset 10-8 #4 Feb 23, 1995 (869,310,162,00) - Restore to original synthesizer setting. Mar 10,95 +35us Site 1Hz offset Mar 20,95 " -50ns Site1Hz adjusted. Dec 6,95 19:49UT 86,716,377,865 Offset 10-8 (#5) Dec 7,95 21:42UT 86,931,004,000 -922us Adjust rate (#6) Dec 7,95 21:45UT " 0.2us Adjust offset (#7) May 17,96 " OFFSET ADJUST(#8) May 22,96 21:19UT 86,716,365,666 Change rate by 10-8 for GBTIES3 run. May 23,96 21:36UT 86,931,004,000 Restore rate. Oct 22,96 17:07UT 86,930,991,200 Adjust rate to match GPS. Jan 2, 98 15:28UT 86,930,983,000 Decrease rate to match GPS. Oct 29, 98: no change Move equipment to Reber Lab: GBT equipment room. March 25, 2002: no change Adjust VCO voltage to near 0 (was > 1 volt) April 5, 2002 86,930,981,000 Decrease rate to match GPS. (#9) April 13, 2004 no rate change ~50ns Adjust offset of TRAK master clock (previously offset was ~500ns Aug 11, 2004 no change Bryan Owings adjusted IF amp and VP. May 04, 2005 86,930,982,500 Increase rate synthesizer to match GPS. (#10) June 08, 2005 86,930,983,000 Increase by +500 counts to counteract 2nd deriv. Sept 2, 2005 rate changes by ~5x10^-14 Power supply failure - but power not lost [10A] Oct 27, 2005 no change 10:00 UT turn off auto-tune (#11) Oct 28, 2005 no change 14:40 UT turn auto-tune back on Oct 28, 2005 no change ~200ns Change TRAK 1pps to near zero. Nov 4, 2005 no change Install new 24v power supplies and install new batteries. Nov 15, 2005 86,930,984,000 Adjust synthesizer. Offset to UT continues at about -5.2ns/day Jan 31, 2006 86,930,986,000 Adjust synthesizer to reverse trend of offset. Aug 16, 2006 86,930,986,500 Increase synthesizer to match rate to GPS. Feb 02, 2007 86,930,987,500 Increase synthesizer to match rate to GPS. July 03, 2007 86,930,988,500 Increase synthesizer to match rate to GPS. December 11, 2007 86,930,988,800 Increase synthesizer to flatten out time diff curve. March 27, 2008 86,930,989,600 Increase synthesizer rate. April 03, 2008 no change Adjust VCO voltage from 1.136 to 0.300 (about 1:30 pm). August 04, 2008 Site Time and all frequency references switched over to the Rubidium standard. TRAK clock reset. August 05, 2008 Patrick Owings replaced a resistor and changed the batteries. Problem had been indicated by "REGISTER" getting near max value of 9.8v. REGISTER now about 5.5 August 06, 2008 switch time/frequency references back to the ST maser. 15:20 UT resync and re-set TRAK no change done to synthesizer December 04, 2008 86,930,990,400 Increase synthesizer +800 counts (15:40UT) February 18, 2009 86,930,990,900 Increase synthesizer +500 counts (19:00 UT) July 27, 2009 86,930,990,100 Decrease synthesizer 800 counts. (17:47 UT) Decem 15, 2009 same Change GPS cable: site1Hz-TAC -167 ns (17:00 UT) May 18, 2010 86,930,990,600 -390ns Increase by 500 counts. (16:40 UT) (offset Site1Hz vs TAC -390ns, not changed, just recorded here) December 21, 2010 same New GPS antenna installed on the roof of the control building. March 25, 2011 same GPS out of service due to a short in the antenna cable from water in a connector. Antenna cable bad starting 03:00 UT. Restored to service 16h UT. December 22, 2011 same -50ns Power glitch in timing rack affected siteTime computer, (15:00 - 22:00 UT) TRAK master clock and TAC. Reset TRAK master clock. Time offset changed by about 100 ns. January 4, 2012 same +30ns Replace batteries in the timing center UPS (not in the maser) Reset time in TRAK master clock. January 18, 2012 same none Maser battery pack replaced. (16:00UT) January 26, 2012 86,930,991,300 no change Increase synthesizer 700 counts to correct (16:10 UT) for -2.6ns/day wrt UTC. The recent battery changes apparently had no effect on the maser rate. November 13-15, 2013 no change offset adj Power outage: apparently maser batteries may not have held. Rate wrt GPS very high after power back on. Bryan Owings advised that the register value had changed from about 8v before the power problem to 4.5v Mike reset the register about 9:45 AM, Nov 15th. TRAK offset adjusted about 1:45 PM, Nov 15th (EST) December 10, 2013 no change no change Maser Batteries replaced at 3:05 pm (Mike) January 21, 2015 86,930,991,900 no change Increase synthesizer by 600 counts to adjust for about -2.5ns/day wrt UTC. March 6, 2015 86,930,992,400 no change Increase synthesizer by 500 counts (half of what would be needed for -3.3ns/day rate) Sept. 11, 2015 86,930,991,900 " Decrease synthesizer by 500 counts to reduce slope of UTC vs local master clock. (half of +3.63ns/day rate) March 22, 2017 86,930,993,900 " Increase synthesizer by 2000 counts (19:50 UT) to flatten Maser vs GPS plot. April 6, 2017 86,930,995,900 " Again increase synthesizer by 2000 counts (14:50 UT) to flatten Maser vs GPS plot. April 18, 2017 86,930,997,900 " Again increase synthesizer by 2000 counts (14:00 UT) to flatten Maser vs GPS plot. May 1, 2017 86,930,999,900 " Again increase synthesizer by 2000 counts (15:00 UT) to flatten Maser vs GPS plot. June 26, 2017 same reset to near zero. Register adjustment. Mike moved the green wire (1400UT) from pin 7 to pin 6. Register reset to ~4.6 TRAK clock synchronized to CNS_GPS 1pps. June 30, 2017 +1sec TRAK clock set to correct time (it was 1 sec off) (8am) (10am: set to UT hour) June 30, 2017 86,930,993,900 Synthesizer lowered by 6000 counts. July 08, 2017 same 62 Power loss on TRAK master clock ~10:12 UT had to cycle power again to synchronize the IRIG. 1pps reset and date/time set by 15:35 UT July 13, 2017 86,930,992,000 " Adjust synthesizer to match drift wrt GPS. July 14, 2017 same Another power loss on TRAK maser clock, 1pps and time/date reset (19:55-20:14 UT) July 18, 2017 Site power outage, TRAK reset again (out: 09:05-10:23 UT) July 22, 2017 UPS glitch, TRAK reset again July 24, 2017 Connect TRAK power to new UPS, TRAK reset again. August 1 to Aug 11, 2017 Sent CNS_GPS receiver to the manufacturer to be updated. August 7, 2017 Mike replaced the maser batteries, 2pm. September 29, 2017 TAC receiver goes belly-up. October 3, 2017 CNS_GPS connected in place of TAC (mjd:58029) Note: CNS 1pps output connected to time comparator X1; CNS 1/100pps output connected to time comparator X3. Both 1pps but about 7 ns difference. December 14, 2017 CNS_GPS: set "intentional extra early offset" to 0.089 December 21, 2017 CNS_GPS: change "intentional extra early offset" to 0.019 January 26, 2018 86,930,994,800 Change synthesizer by +2800 counts to remove drift wrt GPS. March 22, 2018 same ~ -3ns Replace UPS power backup; reset TRAK clock August 23, 2018 Bryan Owings adjusted the VCO voltage from 1.1 to 0.2 August 23, 2018 New MicroSemi maser installed September 7, 2018 Install new CNS GPS receiver (logged as "CNS2018") September 7, 2018 Replace GBTime computer with Windows 10 machine September 11, 2018 86,930,992,600 Change synthesizer by -2200 counts to remove drift September 11, 2018 Set parameters in the CNS_GPS September 12, 2018 Set parameters in the new CNS_GPS [see note ##12 below] September 18-19, 2018 Chris configured new CNS receiver to be an ntp server. September 20?, 2018 New CNS_GPS parameters had to be set again. April 23, 2019 86,930,994,600 Adjust synthesizer by +2000 counts. May 15, 2019 86,930,993,940 Adjust synthesizer by -660 counts Dec 12, 2019 86,930,994,980 Adjust synthesizer by +1040 counts Sept 28, 2020 86,930,995,806 Adjust synthesizer by +826 counts Jan 20, 2021 86,930,996,130 Adjust synthesizer by +324 counts VCO phase voltage was 0.075 V ---------------------------------------------------------------------------------------------------------------------- ** NOTE: 3 high order digits omitted from synthesizer listing, for example, the first line would read in full: 869 3104 5259 ## Offset maser rate by .05HZ(at 5MHZ) for NAPS2 VLBI run involving both the 140-ft and 85-3. #3 Dec 9, 1994. Sigma Tau engineers adjusted the cavity servo to bring the cavity register into nominal range. Offset ST-GPS changed from about +0.8 to +1.5 us. Synthesizer and 1PPS delay not changed. #4 Offset maser rate by -.05HZ(at 5MHZ) for GBTIES VLBI run involving the 140-ft, 85-3, and the new 20-meter. #5 Offset maser by -0.05Hz at 5MHz for GBTIE2 run including 140-ft, 85-3, and 20-meter. #6 Adjust rate to approximate GPS. Offset grew to -922us while running at offset rate (#5). #7 Adjust Site 1pps offset to be close to GPS. #8 TRAK lost time due to power glitch. Maser rate not affected. TRAK 1pps adjusted. #9 Rate Site1Hz to TAC was +8.57 ns/day for the year of 2001. Decreased synthesizer by 2000 counts, corresponding to 8.05 ns/day. #10 Rate Site1Hz to TAC was -5.9 ns/day for 1st 80 days in 2005. Increased synthesizer by 1500 counts. #10A Rate changed spontaneously by about 5x10^-14. Coincident with failure of one of the two 24v power supplies. But power was not lost because there are 2 redundant supplies. #11 Auto-tuning produces sidebands at 28 Hz -- a problem for radar observers calibration. Hence the auto-tune (or dither) was turned off for 1.5 days. During the time it was off, the maser rate was about 2.3x10-11 different than before. The rate went back to the previous value after turning on the dither. #12 Sept 11-12 2018: When the new maser was installed (Aug23), power was off to the timing rack briefly so the GPS receiver forgot all its settings. The settings of the old CNS-GPS were re-installed on Sept 11, and the same settings were put into the new CNS-GPS on Sep 12. Summary of settings: Reference position: lat 38.4313096, lon -79.8192280, alt 821.82 GPS mode: 0D timing : cable delay=57 ns, receiver delay=37ns, early offset=0.019 Updated site time inputs: X0 = Site 1Hz (from TRAK clock) X1 = CNS_GPS1 (1pps output; same as previous CNS_GPS) X2 = CNS2018 (new GPS receiver, 1pps output) X3 = CNS_GPS2 (1/100pps output from old CNS receiver) X4 = MicroSem : 1pps from new MicroSemi maser Y0 = GBT_VLBA Y1 = RA = round trip to 140' Y2 = GBTRtn = round trip to GBT.