Using DT to correct PC Clock
- Meinberg NTP is great. It is a manual operation, but it can be used to add or subtract seconds from the PC clock based on DT values in WSPR. Problem. If the PC clock is off by more than a few seconds, you don't receive anything and thus don't have DT values to work with. It would be handy to have a "3 minute" mode for WSPR. It could hunt for and find the start of transmissions. This would allow for an initial PC clock correction.
RE: [wsjtgroup] Using DT to correct PC clock
This can be easily accomplished with Meinberg NTP. It is a *nix NTP client ported to Windows, and has the advanced features that are normally seen with *nix NTP clients.
This client allows you to use multiple NTP servers for time sync. It can throw out receptions from time servers that are out of line. Of the time signals received that are perceived as accurate, it averages these timings and the result is used to set your PC time. Any adjustments (DT) are tracked over time, and automatically applied to your PC time. This is very valuable when you lose the connectivity to receive timings from your NTP servers.
FWIW, I am not associated with Meinberg, just a satisfied user for several years J
73 de WY5R - KD
From: email@example.com [mailto:firstname.lastname@example.org] On Behalf Of ltj_designs
Sent: Thursday, August 26, 2010 8:05 AM
Subject: [wsjtgroup] Using DT to correct PC clock
I have seen several options for setting the system clock on a PC for the time-synchronized digital modes like WSPR, including NTP, WWV/CHU, and GPS. I have not seen a discussion about using the time difference (DT) based on received signals. For the moment, I would like to bypass the discussion of why not use these other methods and learn what options exist for using the DT.
I recently took my laptop to West Virginia and ran WSPR as a portable station. After 2 days the average DT value was about 5. I could not find a good way to accurately subtract 5 seconds off of the system time. I think Unix has commands to directly adjust either the system clock or the hardware clock. I thought of booting Umbunto temporarily to adjust the hardware clock, then rebooting Windows XP. (The WSPR install on Linux seems daunting, so I want to delay that undertaking.)
It seems desireable to build DT averaging and clock synchronization into the WSPR application. Many stations do not have continuous access to other time standards. What if 50% of the stations used a true time standard and 50% used DT averaging? Would the net effect be to keep all stations better synchronized? That might take some modeling to predict. What if we add 1 bit to the WSPR protocol that indicates if the transmitting station's clock uses an absolute standard or a relative (average DT) value. Receiving stations could choose to average values from absolute sources.
Andy Mitz WA3LTJ