Email: Password: Remember Me | Create Account (Free)

Back to Subject List

Old thread has been locked -- no new posts accepted in this thread
Andy Neil
02/11/12 04:39
Read: 514 times

#185834 - Really??!
Responding to: ???'s previous message
Armin Kashahyah said:
Im so frustrated that i cant find any resource about this

You can't find any resources - really?!

I had never heard of "WWVB" before today, but Google quickly showed me this page:

NIST, the US National Institute of Standards and Technology, said:
NIST radio station WWVB is located on the same site as WWV near Fort Collins, Colorado. The WWVB broadcasts are used by millions of people throughout North America to synchronize consumer electronic products like wall clocks, clock radios, and wristwatches. In addition, WWVB is used for high level applications such as network time synchronization and frequency calibrations.

So it's a time standard transmission - like MSF from our NPL (National Physical Laboratory):

That NIST WWVB page gives you a descritption of the signal:
WWVB continuously broadcasts time and frequency signals at 60 kHz. The carrier frequency provides a stable frequency reference traceable to the national standard. There are no voice announcements on the station, but a time code is synchronized with the 60 kHz carrier and is broadcast continuously at a rate of 1 bit per second using pulse width modulation. The carrier power is reduced and restored to produce the time code bits. The carrier power is reduced by 17 dB at the start of each second, so that the leading edge of every negative going pulse is on time. Full power is restored 0.2 s later for a binary 0, 0.5 s later for a binary 1, or 0.8 s later to convey a position marker. The binary coded decimal (BCD) format is used so that binary digits are combined to represent decimal numbers.

The time code contains the year, day of year, hour, minute, second, and flags that indicate the status of Daylight Saving Time, leap years, and leap seconds. For more details, view the WWVB time code format.

WWVB identifies itself by advancing its carrier phase 45 at 10 minutes after the hour and returning to normal phase at 15 minutes after the hour. If you plot WWVB phase, this results in a phase step of approximately 2.08 microseconds.

The link takes you to this picture of the frame format:

And there's a whole load of links at the bottom of the page:

WWVB Radio Controlled Clocks: Recommended Practices for Manufacturers and Consumers
A 64-page booklet containing recommended practices for WWVB radio controlled clock manufacturers, plus tips for consumers attempting to troubleshoot reception problems.

NIST Time and Frequency Services (NIST Special Publication 432)
A detailed 80 page overview of NIST time and frequency services and how to use them. Chapter 2 is all about WWVB.

How Accurate is a Radio Controlled Clock?
A discussion of WWVB radio controlled clock accuracy from the Horological Journal, March 2010.

Frequently Asked Questions
Answers to frequently asked questions about the NIST Radio Stations

Manufacturers of Time and Frequency Receivers
Links to manufacturers of WWVB and other time and frequency receivers

All this from just one hit (in my case, the very first hit) on Google!

So there is plenty of information available - was there something specific that you wanted to know...?

I would certainly endorse Michael's recommendation that you obtain a module to start with - then you can use that as your point-of-reference for further work...

List of 14 messages in thread
Help! Doing a WWVB Radio-Synchronized Clock with MCP3004      Armin Kashahyah      02/10/12 12:46      
   Difficult to find resources...      Daniel Contarino      02/10/12 13:46      
      MCP3004 is a Microchip A/D Converter!!      Andy Neil      02/11/12 05:00      
      We use a peak detector to convert signals from the radio...      Armin Kashahyah      02/11/12 14:25      
         RE: I have no idea how to start      Andy Neil      02/11/12 14:58      
      We use a peak detector to convert signals from the radio...      Armin Kashahyah      02/11/12 14:27      
         Why?      Neil Kurzman      02/13/12 14:47      
            Yes, There is AM!      Daniel Contarino      02/13/12 17:44      
               Ok But      Neil Kurzman      02/13/12 22:57      
               Comparator      Per Westermark      02/14/12 05:19      
   Strong Suggestion        Michael Karas      02/10/12 17:54      
      Is it still available?      Andy Neil      02/11/12 04:42      
         Maybe EOL      Michael Karas      02/11/12 07:10      
   Really??!      Andy Neil      02/11/12 04:39      

Back to Subject List