[time-nuts] LF time signal emulation

Brooke Clarke brooke at pacific.net
Mon Apr 30 11:00:27 EDT 2007

Hi Jim:

I thought JJY was in Japan?

I think the crew from what was called Temic has formed a new company called 
C-MAX.  The C-MAX LF time signal receiver chips support automatic tuning to 3 
frequencies using the same loop antenna by switching caps.  The ICs also know 
the protocol for the various LF time stations, so products that use the C-MAX 
chip will work world wide (if there's a signal), but older products are 
typically specific to one frequency and protocol.

They have app notes on how to design the loop.
Larger loops are more sensitive than smaller loops.

Joseph's suggestion of making a resonating loop is worth a try.  Remember to 
orient the vertical loop both in azimuth and maybe tilt.  Maybe just wind it 
around you house top to bottom.

Have Fun,

Brooke Clarke

Palfreyman, Jim L wrote:
> Folks,
> Living in Australia we are generally out of range of the LF time signals
> (WWVB, JJY etc). However I recently purchased a multi-band travel clock
> off ebay for $30 and found I could get JJY in Tasmania.
> Excitedly I purchased a Casio multi band G-Shock wristwatch (which I
> really like), but have had little luck in getting it to pick up an LF
> time signal.
> Since I already have tenth of millisecond accuracy locally in my house
> based on a GPSDO, what I would like to do is build my own local LF
> transmitter (reception within say 100m) and emulate the time codes of
> one of the stations so my watch (and any future similar purchases) lock
> on to the local signal each night.
> Because I like to stand on the shoulders of giants, has anyone actually
> done something like this? My skills are more in software development and
> hardware digital logic rather than in LF radio transmitters - so any
> help or pointing in the right direction would be appreciated.
> Regards,
> Jim Palfreyman
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