[time-nuts] Timing receivers' observations of leap second

James Maynard james.h.maynard at usa.net
Sat Dec 31 19:53:12 EST 2005

Here in Salem, Oregon, USA, I observed two timing displays at the moment 
of the leap second: the display of an Ultralink Model 333 WWVB Decoder 
and that of some PC software from CNS Systems, Inc. I was also listening 
   to the audio of the HF time and frequency stations, WWV and WWVH, at 
that time.

Ultralink Model 333:

My UltraLink model 333 WWVB receiver has not yet recorded the leap 
second, probably because its antenna is in too noisy a location to 
receive WWVB's 60 kHz signal at this time of day. The display still 
indicates that a leap second is pending, and it still indicates an 
offset from UTC to UT1 of -0.6 s.

Apparently the Model 333 WWVB receiver's software does not apply the 
leap second to its display at the scheduled time, althouth it does know 
that a leap second is pending.  It seems that this software does not 
apply the leap second until it actually receives a signal from WWVB with 
the newly adjusted UTC timescale.

The SynTac32 software (from CNS Systems, Inc.) that displays the output 
of my Motorola M12+ timing receiver waited a couple of seconds after the 
leap second occurred before displaying the correct time, including the 
leap second adjustment.

My guess is that this display software, like that in the WWVB receiver, 
does not apply the leap second adjustment at the scheduled time, but 
waits until it receives messages from the M12+ that reflect the newly 
adjusted UTC time scale.

The Motorola M12+ itself, however, as indicated in the posting from 
Christopher Hover <ch at murgatroid.com>, does apply the leap second at the 
scheduled time.

James Maynard
Salem, Oregon, USA

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