Again, thanks for all the great feedback and suggestions. > Are you familiar with these devices which I just found this week? > https://tentaclesync.com/products
Yes, that's one of the lower cost commercial units available. Another is the NanoLockiIt by Ambient <https://www.bhphotovideo.com/c/product/1333498-REG/ambient_recording_acn_nl_nanolockit_miniature_timecode_synchronizer.html>, which is company that's been making timecode products for many years. Compared to more traditional prices for timecode generators, these are relatively inexpensive at about $300. However you need at least two, or more generators to be useful, so that adds up pretty fast for an amateur videographer, or starving film school student. In contrast, BOM for the design I'm working on is less than $30 (the TCVCXO being, by far, the most expensive part.) My plan is to also write a desktop application, probably in Java to make it portable, that the person building the devices could use to perform the initial calibration and also setup various options. So, the NTP-based solution is attractive in that it doesn't require any additional hardware. I'm a Mac user so, after a bit of reading the NTP implementation on the Mac, I tried a few experiments. Typing "ntpq -p" in the terminal app produced this response: remote refid st t when poll reach delay offset jitter ============================================================================== *usdal2-ntp-001. .GPSs. 1 u 428 1024 377 51.131 1.944 1.153 and typing "ntpq -c rl" printed out: associd=0 status=0615 leap_none, sync_ntp, 1 event, clock_sync, version="ntpd firstname.lastname@example.org Fri Feb 5 17:38:17 UTC 2016 (124.60.2~39)", processor="x86_64", system="Darwin/16.7.0", leap=00, stratum=2, precision=-20, rootdelay=51.131, rootdisp=34.160, refid=220.127.116.11, reftime=de7ba9c1.937e5f86 Fri, Apr 13 2018 15:12:17.576, clock=de7badf7.39f8d36a Fri, Apr 13 2018 15:30:15.226, peer=7077, tc=10, mintc=3, offset=1.944153, frequency=25.163, sys_jitter=0.000000, clk_jitter=0.745, clk_wander=0.001 I believe that the "precision" of -20 value on the 4th line is supposed to be interpreted as 2^-20 seconds which, if my math is correct, works out to be a precision of about 1 PPM. Is that correct? If so, it would seem like I should be able to use my system's internal clock to perform a "tweak" in around 10,000 seconds, or a little less than 3 hours. Does this seem correct, or have I missed something? Alternately, if I included a GPS receiver in the design, the whole process could be done within the device, which would probably be the easiest approach to calibration for the person building one. This would increase the cost and make the device larger, but users could then maintain calibration by periodically keeping them plugged in for a few hours. Or, perhaps I could just design a 2nd board for a GPS "calibrator" module that could be plugged into the timecode generators to calibrate them. Hmm... lots to think about. Wayne _______________________________________________ time-nuts mailing list -- email@example.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.