OK a slight update to this email. I will be darned the 8170 locked up and decoded time after about 4-5 hours on the east coast! So there is something going on bias in the BPSK code stream that allows this to actually happen. So on the transition testing I never left the clock running this long. Figured it was as advertised. Regards One surprised Paul. WB8TSL
On Sat, Jan 19, 2013 at 12:01 PM, paul swed <[email protected]> wrote: > Good morning to the group. > I did not think that FEBO would be operating. > I wanted to respond to the 8170 discussion that had been running but > typing on itty bitty screens is tough. > So now that I am on a real keyboard I can do a better job. > The discussion actually went a bit askew in the fact that evidently some > 8170s lock to the new wwvb BPSK signal. > But here is the facts. Cheap AM demodulated receivers will and do work. > These do not use phase tracking for data recovery. > Any phase tracking receiver can not work with the new format. This > includes spectracoms, HP, Tracors, Fluke, and True-time. There may be > others, I have them all accept the true-time. This is stated by spectracom > and NIST and understanding the new modulation scheme it makes sense why > they don't work. > So the very real question isn't why are many of our 8170s not working. Its > why some 8170s do work apparently without modification? > As I think about this its the perfect time-nuts enigma. > > On time-nuts there have been several comments on squaring techniques and > if you are just looking for time recover for an 8170 that is a simple > solution that should work. You do not need long term system stability to > recover the time. However if frequency/phase recovery is your interest this > approach is quite poor requiring very favorable propagation with consistant > very high signal levels. > Some of us time-nuts have those conditions. Most don't. > I seriously went through the easy squaring methods. They all work per > theory on the bench but totally fail in real world 60 Khz reception due to > the following reasons. (I am east coast with 60uv day signal levels) > Impulse noise, Amplitude modulation, and propagation dynamics. One missed > cycle and the output phase flips. On the charts you end up with essentially > noise. Oh how I wanted those approaches to work. Simple, easy, cheap. > > So thats where I am at. Why would any timing receiver that uses phase > recovery actually work to recover time (Phase is out). Something to be > learned here, but I have no way to actually figure it out. I have had my > 8170 on for 30 min and no lock. It used to lock in about 1-2 min before the > signal changed. I tested this during the transition period and it > consistently failed. > > Looking forward to the knowledge this group has to answering that > question. Does any math support a receiver thats off frequency to recover > the time signal. I might guess that there is and that the 8170s that happen > to work do so by this method. > Hey if it makes the 8170 work I will offset the oscillator. Heck thats an > easy fix. > Regards > Paul > WB8TSL > _______________________________________________ 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.
