From: "Larry Cochrane" <cochrane@..............> Subject: Re: GPS time error Date: Sat, 8 Dec 2001 12:19:22 -0800
Hi Tom,
I assume you have already enabled GPS timing by going to the System Settings Dialog box and selecting GPS for the Time Reference Type. Also make sure the Reference Offset is set to zero. The next thing to do is check the winsdr.log file for any errors. You can also monitor the GPS or WWV timing process by opening the Log File Viewer. You open this window by going to the View / Log File / View Log File menu items. This will open a new window that WinSDR updates as it writes info to the log file. The log file is called winsdr.log and its located in the same directory as winsdr.exe.
So that I can see what's going on please do the following. Exit WinSDR and delete the current log file. Restart the program and let it run for about an hour. Then send me the log file so I can check it out. Also, how are you comparing the time?
If you have a oscope with two channels you can do the following to check the timing accuracy. Connect one channel of the scope to the 1 pps output of the GPS receiver. The other channel should connect up to pin 12 of the 25 pin IO connector on the Serial A/D board. You can use pins 13 or 25 for the ground. If things are working correctly you should see the rising edge of the two signals within a few milliseconds of each other. You can then connect one channel of the scope to the audio output of you short-wave receiver and look for the 1 PPS signal. It should also be within 10 ms of one of the other timing references.
Since the above process would not show a problem if one of the timing sources is exactly 11 seconds off you could do the following experiment. Take one of analog channels and connect it up to TP1 on the A/D board. This test point is near the LM567 tone decoder chip. Using GPS as the timing reference, and connecting up the short-wave receiver to the WWV input connector, record a few minutes of data when you have good WWV reception. Using WinQuake to look at the data you should see a falling edge of the signal at the top of the minute. This should tell you if you are off by more then 1 second.
Hope this helps......
-Larry
----- Original Message -----
From: Tom Frey
To: winsdr@..............
Sent: Saturday, December 08, 2001 9:05 AM
Subject: GPS time error
Greetings
I have only recently (yesterday) set up WinSDR using Larrys' PSN-ADC-SERIAL board and 3 channel Amp/Filter board. I am using the GPS time option but am unable to get an accurate time even though it shows that it is (time) locked. When I compare the time with a live WWV signal my time is almost exactly 11 seconds ahead of WWV.
Have I missed a setting somewhere? I know very little about GPS. I have tried checking the GPS time using WinOncore and the time is accurate using it
thanks tom