[time-nuts] WWVB and spectracom 8170 receivers etc

[paul swed]

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 <paulswedb at gmail.com> 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
>