[time-nuts] Re: Syncserver S300 LFR 60 kHz WVVB

[Bob kb8tq]

Hi

Quick summary of WWVB changes:

As time has gone on, the world has fallen in love with switching power 
supplies. Often these run at 40 to 80 KHz and create a ton of RFI. That
has made WWVB more difficult to receive. Also MSF propagates into 
the northeast at some times creating issues as well. 

They went to a phase modulation setup to improve the ability to decode
the signal. It most certainly did that. They kept enough of the old AM
modulation to allow the typical wrist watch to demodulate the signal.
What this *did* do is to create a signal that lab gear trying to phase lock
to the signal no longer worked. 

Just how the problem shows up on this or that piece of gear is very much
a “that depends” sort of thing. Even with the old signal, getting outdoor
antennas set up properly and tracking down issues was a bit of a pain. 
Sorting that out on top of phase mod stuff … yikes. 

Best guess: the unit is trying to phase lock and it cant. 

There is only one outfit that seems to have jumped on the bandwagon
with a chip for the new format. You can get boards that have the chip
on them. They are not going to help much with phase locking. ( and 
AM demodulation still should work ….). 

Various folks here on the list have done DIY projects to feed an old
style signal into this or that device. There are a variety of practical issues
and decisions to be made if you go that route.

Bob

> On Sep 2, 2022, at 7:48 AM, Todd Smith via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> Hello
> 
> 
> 
> I stumbled upon this list while looking for some information to refurb a
> couple of older Symmetricom (Microsemi) S300 Syncserver NTP appliances
> equipped with the optional LFR 60 kHz kit.  I believe that I am receiving
> signal at my location since the LED on the back of the unit beside the LFR
> antenna  port blinks while it is running.  It shows unlocked in the GUI
> since it is apparently not decoding the signal.
> 
> 
> 
> I have read where in 2012, NIST changed the format for WVVB from AM to a
> phase modulation and some receivers might not be able to decode the phase
> modulation.  Do you think that is the case here?  I need to get another
> WVVB receiver and test that I can receive signal at this location but I am
> high enough and away from interference sources so that leads me to believe
> that I am probably receiving signal.  Over 72 hours on the graph in the GUI
> and it never decodes a signal yet the back blinks the entire time.
> 
> 
> 
> If phase modulation is the issue; is there a demodulator that I can get to
> correct the signal format?
> 
> 
> 
> Thank you for your time
> 
> Todd Smith
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