Hi

The simple answer is that WWVB still has the good old AM modulation on it.
Any of the old time receivers will work just fine with the current broadcast
format. There are a number of them that show up on the surplus market. The
gotcha is those receivers that wanted to get both frequency and time. Those
are toast without some heroic modification efforts.

The world is still waiting for the magic chips that will decode the new format
to show up on the market. The issue is that you could do a design that uses
a  hundred dollars of parts. Poof! you have a commercial device to sell.
Next day out come the magic chips for < $1 and 80% of your BOM is replaced.
Your competitor now has a unit on the market for 1/5 your price. You better hope
you recovered all of your up front costs before that happens. You also now have
a group of customers that expect at least 20 years of free updates and free  support
on your gizmo ….and it’s a dead end for you. Zero dollars in on that design and many
many dollars out every year. Simple answer is not to go down that road. Wait for
the magic chips to show up. That’s the way it’s worked for at least 40 years.

Basement lab wise, sure you can come up with this or that to demodulate the signal.
That’s been done and is being done. That’s a long ways from a commercial rack mount
gizmo that “just works”.

On a more practical basis, GPS is traceable to UTC and to USNO. By law USNO is the
authority on time in the US. NIST is the authority on frequency. That distinction goes back
to a long gone era when time was a “navigation” thing and frequency was a “commerce”
function.  In either case, you need to be able (legally) to trace via a valid path to whatever
each of them say is correct. These days there are lots of paths. They all work and all
have tolerance estimates on them. On a global basis you need to trace back to UTC and
BIH. It’s the same idea only one level higher.

Bob

Burt you missed nothing. It would appear that all good intentions did not
lead to new business. So there you go the old receivers useless and no new
ones made.
Certainly all of the old ones can be made to work using the cheatn dpskr
shared with time nuts. But boy compared to the gpsdo's this lazy time nut
likes the simplicity and economics. Sure I can't say I am the first kid on
the block with a USFS but that hasn't been much of a topic lately.

I do fire up the old wwvb receivers just to make sure the cheatn dpskr
works and that they still do. But 99.9% of the time its the gpsdo these
days. Its there until it isn't.
Regards
Paul
WB8TSL

On Fri, Feb 10, 2017 at 3:47 PM, Burt I. Weiner biwa@att.net wrote:

Hi

One could make a WWVB “new modulation” receiver with some sort
of MCU demo board and a handful of parts. It would be fine for a basement
lab / learning sort of project. Given the way the semiconductor world works,
the longer you wait to start that project, the better a board you will have
as the base of the project.

At the end of the project with everything working fine, you still have WWVB
as the “source”. Propagation issues still limit what you can achieve.
MSF (as far as I know) is still on the air. That still is going to cause issues
if you are in the New England area. Miami is still a long way from Colorado.
If you happen to live in Denver, not much of a problem at all.

How many people want to spend more than a year on that sort of thing when
a < $10 GPS USB dongle would do as good a job? It’s a back burner project
here. There isn’t a real big push to get it onto the front burner. Yes, following
the masses like that is a bit sad. There are things that would be learned doing
this sort of thing. Some of them would be about WWVB. A few of the learnings
would be about GPS. As others have very correctly pointed out, diverse sources of time
are a good thing. We are headed towards a GPS monoculture.

Bob

In message 2126B261-3E4E-46D4-9181-1FB368244304@n1k.org, Bob Camp writes:

With reasonable OCXO as timebase, it would do much more than that.

SRS sold the SR700 Loran receiver as a "Cesium replacement".

Current boards are more than capable of this, a 12 ADC at 1MSPS is plenty.

Unless you're a total programming beginner, you will have carrier lock in
a week:

• Configure ADC for 1MSPS

• Interrupt routine: exponentially average the samples into a 50[1]
  bucket circular buffer

• Control-Loop (not time-critical):

  • Multiply 50 buckets with synthetic sine/cos function,

  • Average the 2x50 results to get I/Q phase signal.

  • Feed phase into PLL to steer OCXO.

  • Bonus: Decode timegram.

I did that with Loran-C, which is a much harder signal, I did it
8 years ago, and I did it in two weeks.

Poul-Henning

[1] If you use a platform with enough memory, for instance a BBB,
use a one million (=full second) buffer instead, you will be
able to pull any and all VLF signals out of it.  For instance
the US navy runs a couple of stations with frequency stability
comparable to WWV.  On a BBB you could even add a FRI length
buffer also, to receive the Wildwood Loran-C.

--
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