[time-nuts] WWVB and spectracom 8170 receivers etc

[paul swed]

One more comment and this goes in the doaaa area.
WWVB during the transition phase was going to revert back to the old format
for 1 hour per day. I thought that would stop at the turn of the year. Is
it possible that behavior is still going? Time for an email to NIST.
Regards
Paul

On Sat, Jan 19, 2013 at 3:32 PM, paul swed <paulswedb at gmail.com> wrote:

> 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
>>
>
>