David L. Mills said the following on 10/10/2007 08:26 PM: > The Spectracom WWVB radios we have used to do an excellent job; however, > the claimed accuracy was only 0.1 ms, mostly because the computer used > for demodulation was so chintzy. Sadly, WWVB is dead here because of EMI > generated by hundres of UPS systems all over campus. I'd be curious to > know if this has also affected DCF-77 users.
I'm still running two Spectracoms here in Ohio (one a WWVB timecode receiver, the other a WWVB disciplined oscillator) and they work very well, though not as well as either LORAN-C or GPS receivers. One or the other of the receivers loses lock momentarily perhaps every two or three weeks, but otherwise they are solid. When lock is lost, there is a short blip of about -30 milliseconds, with rapid recovery to within a millisecond or two. I suspect that blip could be minimized by either realigning the VCO in the unit, or using an external 10 MHz source instead of the simple crystal in that VCO. There was a factory option for external reference input, but mine doesn't have that. Yet. The 0.1 microsecond accuracy Dave mentions is also tied the the method Spectracom uses for steering; it only adjusts time in 100 microsecond steps, so that inherently limits the accuracy. One reason I like keeping the WWVB receiver around is that it give me something I can easily say is "NIST traceable" without going through post-correction. John _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
