View Full Version : Decoding UK's NPL MSF Time Signal

09-01-2009, 14:52
My first real post, so be gentle with me!

Attached is a programme that decodes the time signal provided by the UK's National Physics Lab.This in known as "MSF" and is broadcast from Anthorn, Cumbria,UK. It should be capable of being picked up in nothern and western Europe.

This project came about because my "radio controlled" radio alarm went defunct, but the antenna and its electronics were OK. The clock was similar to the one here http://www.leapsecond.com/pages/sony-wwvb/

In fact the antenna module is pretty much identical, using the Temic U4226B chip.(The datasheet available on the web).

So I thought I'd have a go at decoding the signal, aiming at using the cheapest 'axe.

The resulting code is attached - which doubtless could be improved upon.
It is not a "full" decode of the signal, most importantly NOT parity checking the Time and Date data. (Not enough code-space in the 08M). This may seem "catastrophic" but it seems to work pretty well, despite this.

There is not much hardware involved outside the antenna module.
The output from the U4226B chip is inverted i.e. gives a logic high for carrier off. This I re-inverted using a BC548B transistor switch (100K base resistor, 2K7 load res.).

A setup such as this could be used to contain the "drift" over time of a DS1307 RTC (or similar) - well thats why my radio alarm clock had one!

Hope this code may be useful to someone.

09-01-2009, 15:22
Cheers GP.
I managed to get it up and running in 5 minutes.


10-01-2009, 18:07

You've done a massive amount of work on this project.
All credit to you.
All I'm doing is adding a little bit, to help my poor addled brain cell.

I'm using a 28X1, so, plenty of variables and code-space.
I added three more symbols, using b14-b16.
Then I added the routines I've shown in the screen-shot,
to convert the #BCD to decimal.


10-01-2009, 19:36
As greypower's finished project got somewhat hijacked (mea culpa) and further discussion is going to happen I've moved the discussion to the Active Forum.

Discussion : http://www.picaxeforum.co.uk/showthread.php?t=11334

Finished Poject : http://www.picaxeforum.co.uk/showthread.php?t=11335