In article <2k9rm.10560$ym4.4...@text.news.virginmedia.com>, david- tay...@blueyonder.not-this-bit.nor-this-part.co.uk.invalid says... >
> Keep asking the questions, even if they seem elementary - and I will > try to both provide answers and record them on my Web site for others. > One issue which you haven't addressed (as far as I know) is how the > Faros program uses an accurate time. I take it that the author of the > program gets the time from Windows - he does know that time is > typically only updated once every ten milliseconds, I guess? > NTP doesn't have an API which can tell you the time more accurately > than that, which is a pity because that would be very handy.... > > 73, > David Hi.. Back after getting diverted by my central heating system going on the blink... Re Faros. Good question, well presented, unknown (exactly) at this time! It does run it's own internal software clock, that I do know having asked Alex (VE3NEA) questions about it in the past. That in turn is synched to a reference by NTP (not SNTP) it does not (AFIK) use "Windows" time in any way. (Sadly, he's totally uninterested in making it able to use a local GPS receiver with PPS, or a radio time code RX.) It's own internal timekeeping routines use a Kalman Filter (Think that's what it's called) to determine "true" time from a number of NTP sources. It is also quite "chatty" I expect compared to a true NTP client, as it will poll the NTP server (or selected collection of servers in rotation) about every 10 seconds! Another reason I think a local server would be best :-) Generally it keeps good time, to within a mS or so, as it can reliably tell if a received signal comes the short or long way round the globe, even from New Zealand! (A close call that one though.) However, it (for whatever reason) is not good at handling variable network latency, especially if the flight times to/from the server are different, as seems to be the case at odd times of day at present. With the Meinberg NTP server in the path now, doing the synchronization to the outside world's NTP boxes (for now) things are a little better. At least, it takes longer for the variable latency problem to screw things up, but it also takes longer to recover too. Extra "filtering" in the overall path I guess. (Software algorithms etc in the Meinberg software.) Anyway. After reading all the info here, I now think I know how to do it correctly, setting up the Meinberg program, and overlaying Dave Harts binaries on it, also doing the registry thing pointing at the PPS supporting serial driver, so when I get enough of the right sort of time next time, I'll try again. One thing I picked up on, is the parameters in the NTP config file, regarding poll times. The units of measure are not mS, but 2^n mS, I think? By the time I get my head round all this, we'll have probably lost HF to PLT anyway. Regards to All. Dave Baxter. _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
