John, I am hoping that those iono changes aren't going to be fast enough (< 10 sec) to affect my decoding.
-Lenny On Sat, Mar 26, 2011 at 6:58 PM, J. Forster <[email protected]> wrote: > I used to use WWVB before LORAN came into my life (HP 117A). It was a > PITA. On the east coast (Boston) the signal was erratic and often became > untrackable. About half the time, the receiver lost lock at least once per > 24 hours, making WWVB an unreliable standard. You really need continuous > tracking over several days to be sure of your local standards' aging rate. > > Furthermore, the diurnal phase shifts between day and night are a PITA. > > Boy, I really do miss LORAN. > > -John > > =============== > > > > Lenny, > > > > You are ahead of me by many months. I'm building a WWVB receiver > > also. Actually I expect I will need to build several before I get > > 24x7 coverage. My breadboard works only at night in the So. > > California area. My plan is to place the entire receiver, antenna > > and all on a mast far from the house and use an RS422 serial line to > > send the data back to a computer indoors. > > > > Do you intend to publish your work? I'd be most interested in how > > you decode the signal. I'm conflicted between two approaches (1) To > > declare the signal "invalid" if there is any error at all or (2) to > > try and extract as much signal out of the noise as I can. I may do > > the latter and then have some kind of quality indicator. The WWV > > audio decoder built into the NTP reference implementation can extract > > time code from what sounds like white noise and static to the human > > ear using sophisticated DSP. My first receiver will use #1. > > > > About measuring the PPS.If you had a nice HP Universal counter with a > > computer interface that would be best. You put the PPS from a good > > GPS on one channel and the PPS from WWVB on the other. Lacking that > > and if you only need to get down to uS level you can use two serial > > orts in a Linux box and use PPS line disciplin on each oert the kernal > > will time stamp the PPS when they happen and software can read and log > > the time stamps. Use the command "ldattach pps <device>" for each > > serial port. Good to about 1 uSwhich for WWVB might be enough > > > > > > > > On Sat, Mar 26, 2011 at 1:26 PM, Lenny Story <[email protected]> > wrote: > >> Greetings All, > >> > >> This is my first post to this board. > >> > >> I've completed the first run of a WWVB receiver board and Antenna > >> (custom > >> wound quad). Its an 8051 microcontroller, with a serial port really, but > >> it > >> can decode the signal accurately pretty much all day long. (I'm just > >> north > >> of boston, MA). > >> > >> I'm wanting to evaluate its performance, my guess is i'll have to > >> produce a > >> plot of its PPS. In reading the LeapSecond.com site (awesome btw), the > >> "Allen Deviation" is used. As this is my first technical, experience in > >> this area, is there a resource or method that is preferred by those who > >> know > >> this technology ? > >> > >> The code reports the time delta between each detected second. If i log > >> the > >> PPS deltas for an entire day (or week) of detected signal, is that > >> enough > >> data to start figuring out how to do the "Allen Deviation" calculations > >> ? > >> > >> Any resources can you recommend to figuring out the graphs i need to > >> produce > >> ? > >> > >> Thanks in advance for your help ! > >> -Lenny Story > >> _______________________________________________ > >> time-nuts mailing list -- [email protected] > >> To unsubscribe, go to > >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >> and follow the instructions there. > >> > > > > > > > > -- > > ===== > > Chris Albertson > > Redondo Beach, California > > > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
