Notes from lab book: by John Beale March 2011 Pletronics 26 MHz OCXO OHM40480526 http://pletronics.com/uploads/datasheets/ohm4%205.0v.pdf Tuning voltage of 1.58V from 5V ref through 10k + 500 ohm trimpots in series. PIC 26 MHz-> 1 PPS divider chip: http://www.bealecorner.org/best/measure/time/source/ Phase error from GPS 1 PPS (SKYLAB SKG16B) see: http://www.leapsecond.com/pages/MG1613S/ March 19 2011: installed LT1021B 5V ref (4,997V), fixed 500 ohm pot turn direction, Vt=1.5841 V 0.140 us @ 10:24 pm 3/19 -1.08 us @ 10:34 pm 3/19 Vtune = 1.5820 V -.632 us @ 10:51 pm 3/19 -.040 us @ 11:08 pm 3/19 0.710 us @ 11:33 pm 3/19 0.75 us / 25m = 0.5 ppb slow 21.66 us @ 4:35 am 3/20 20.95 us / 5h2m = 1.16 ppb slow 47.60 us @ 9:10 am 3/20 25.94 us / 4h35m= 1.57 ppb slow 69.29 us @ 2:12 pm 3/20 21.69 us / 5h2m = 1.20 ppb slow 98.43 us @ 7:12 pm 3/20 29.14 us / 5h = 1.62 ppb slow 127.5 us @ 11:20 pm 3/20 29.07 us / 4h8m = 1.95 ppb slow reset offset @ 11:22 pm 26M osc lags 340 ns @ 11:23 pm 3/20 62.6 us @ 7:53 am 3/21 62.26 us / 08h30m = 2.03 ppb slow 163.2 us @ 8:56 pm 3/21 100.6 us / 13h03m = 2.14 ppb slow 465.7 us @ 9:09 pm 3/22 302.5 us / 24h13m = 3.47 ppb slow ddf = -1.33 ppb 2.83 ppb/mV and 3.47 ppb => change tuning voltage by 1.23 mV 1.5819 -> 1.5831 V 26M osc lags 140 ns @ 9:40 pm 3/22 12.72 us @ 8:12 am 3/23 12.58 us / 11h32m = 0.30 ppb slow DAILY DELTA_F: 42.22 us @ 9:15 pm 3/23 29.50 us / 13h03m = 0.63 ppb slow 139.8 us @ 9:01 pm 3/24 97.58 us / 23h46m = 1.14 ppb slow ddf = -0.51 ppb 263.1 us @ 9:42 pm 3/25 123.3 us / 24h41m = 1.39 ppb slow ddf = -0.25 ppb 171.5 us @ 9:48 pm 3/26 -91.6 us / 24h06m = 1.05 ppb fast ddf = +0.34 ppb 180.6 us @ 10:00 pm 3/27 9.1 us / 24h12m = 0.10 ppb slow ddf = -1.15 ppb 181.5 us @ 8:49 am 3/28 0.9 us / 10h49m = 0.02 ppb slow 190.8 us @ 9:22 pm 3/28 10.2 us / 23h38m = 0.12 ppb slow dff = -0.02 ppb 272.2 us @ 9:49 pm 3/29 81.4 us / 24h27m = 0.92 ppb slow dff = -0.80 ppb 327.9 us @ 10:23 pm 3/30 55.7 us / 24h34m = 0.63 ppb slow dff = +0.29 ppb 315.0 us @ 10:04 pm 3/31 -12.9 us / 23h41m =-0.15 ppb slow dff = +0.78 ppb 315.0 us @ 9:54 pm 4/1 0.0 us / 23h50m = 0.00 ppb dff = -0.15 ppb 1152 us @ 11:05 pm 4/4 ss us / 73h11m = 3.18 ppb slow dff = -1.04 ppb 1566 us @ 11:18 pm 4/5 414 us / 24h13m = 4.75 ppb slow dff = -1.57 ppb Vtune = 1.5847 V at 4/5/2011 11:23 pm -> 1.5865 V at 11:30 pm (Vtune adjusted per calculation) 292 ns @ 11:33 pm 4/5 209.4 us @ 10:38 pm 4/6 209.1 us / 23h05m = 2.52 ppb slow th=4.201 kohm 517.3 us @ 8:46 pm 4/7 307.9 us / 22h08m = 3.86 ppb slow dff = -1.34 ppb