The low cost WWVB receivers put out an on/off signal which can be wired up to
a modem control signal.

Many many years ago, I found some software that decoded that.  Or tried to.
I never got it working well enough to be interesting.  Too much EMI or
something like that.

I'm pretty sure it was setup to feed ntpd via SHM, but I never got that far.

--
These are my opinions.  I hate spam.

If the PC's clock is being disciplined by NTP oe "whatever" the WWVB
simulator would not even have to "know" and would just use the system
clock.  So I doubt you will find a simulator that explicitly makes use of
a reference clock.  For your purpose the PC's clock could even be set using
Internet pool servers, typically this gets you to within a couple tens of
milliseconds.  The GPS will keep the PC's clock ate the tens of
microseconds level, You don't need that for setting wrist watch.

One problem is the new phase modulation that WWVB is using.  If you want to
emulate that you might want to use an audio interface that can output the
60KHz RF signal directly.  Most audio interfaces only go up to about
20KHz.    You need the 60KHz interface so you can keep the phase aligned
with the UTC second.

Software would be easy to write, just output 60,000 numbers per second to
the port.

But if you already have a uP that can simulate WWVB why not just add a
little bit of code you read the tie of day over a serial port

On Wed, Nov 2, 2016 at 9:05 AM, Vlad time@patoka.org wrote:

--

Chris Albertson
Redondo Beach, California

Hi Vlad,

There's lots of postings about this in the archives. For playing at home I usually use a GPSDO/1PPS as the time reference and don't worry about how accurate the 60 kHz carrier is. There should be lots of postings in the archives about all this.

The code itself is very simple. See for example:
http://www.leapsecond.com/notes/wwvb1.htm

You can also use PC audio through headphones as a transmitter for both the carrier and the subcode:
https://www.febo.com/pipermail/time-nuts/2011-November/060937.html

/tvb

----- Original Message -----
From: "Vlad" time@patoka.org
To: "Discussion of precise time and frequency measurement" time-nuts@febo.com
Sent: Wednesday, November 02, 2016 9:05 AM
Subject: Re: [time-nuts] WWVB software for PC

Chris,

Thanks for the quick reply ! I am thinking to use something like
Raspberry PI + little "periphery" to transmit on 60Khz. May be General
IO pins and some buffer (like 75179) plus loopstick antenna will do the
trick. I have a NTP server in my lab which sync by 1PPS coming from
T-Bolt. So, the source should be good enough to sync the wrist watch.

The uP project I have - was bought as a kit. So, I am not the
author/creator of that. I just get parts together and put them to the
nice project box.
I think I am capable to create such thing by myself, but its probably
not worth to re-invent the wheel. I think the idea is already "in air"
For example: Circuit Cellar 2014 Digital Archive: Issue 288 July 2014,
page 57-

The phase modulation is interesting feature to have. Its in my "long
waiting list" to have a look to it more closely and probably try to do
something like this.

On 2016-11-02 13:07, Chris Albertson wrote:

--
WBW,

V.P.

Excellent idea to use the harmonics and sound card ! Thanks ! I'll try
to experiment with that. Probably using  some coil instead of headphones
will eliminate the sound at all.
Then whole project will be kind of trivial with almost no HW work
required. Just another "daemonised" process running on my NTP machine
which push the WWVB through the soundcard.
Interesting ! Thanks again !

On 2016-11-02 13:35, Tom Van Baak wrote:

--
WBW,

V.P.