Hi
none of these nist references will download to me in Australia,
is it some sort of national security issue?
cheers,
Neville Michie
On 21/12/2009, at 11:01 PM, Hal Murray wrote:
[email protected] said:
Your ears are correct; the 100 Hz code began in 1960. See:
http://tf.boulder.nist.gov/general/pdf/1670.pdf
http://tf.boulder.nist.gov/general/pdf/1681.pdf
http://tf.nist.gov/stations/wwvhistory.htm
http://tf.boulder.nist.gov/general/pdf/1731.pdf
Fun reading. Thanks.
I think I found a better one:
http://tf.nist.gov/general/pdf/1969.pdf
NIST Special Publication 250-67
NIST Time and Frequency Radio Stations: WWV, WWVH, and WWVB
January 2005
Here is a chunk from page 14:
(postscript page 14, document page 5)
An experimental time code containing year, month, day, and precise
time-of-day began in April 1960 [14] and was made part of the regular
broadcast in January 1961 [15]. This time code, known as the NASA
36-bit
code, was produced at a 100 Hz rate using 1000 Hz modulation.
Believed to be
the first digital time code broadcast in the United States, it made it
possible for the first time for self-setting, radio controlled
clocks to
appear. Earlier radio controlled clocks required human interaction to
initially synchronize. The current time code format (modified
slightly over
the years) was a modified version of the IRIG-H code format. It was
initiated
on July 1, 1971 using a 1 Hz rate and 100 Hz modulation. The new code
included a daylight saving time (DST) indicator [16]. The
telegraphic time
code was also permanently removed on this date.
So the 100 Hz subcarrier (that I didn't remember) didn't start
until 1971.
That was long after I was listening to WWV as a kid.
--
These are my opinions, not necessarily my employer's. I hate spam.
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