What are the purposes of the time transmissions on the short wave bands. They appear to be bleeps but near minuits and hours one can hear data and even voices on some of them. 5Mhz etc. Brian
Wide area frequency standards, the carriers are very accurate. Also wide area coverage of accurate time information.
"fast code" in MSF speak, though I think they have dropped that these days, the "slow code" is easier to decode and less susceptable to noise.
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Can't find the same information on the NPL site but that is a nice mainly text page. 2 bits/second indicated by the duration the carrier is off each second.
Some legistures require a regular voice identification of the signal.
I still have the Maplin kit (not in use). I had it on a system running Interactive UNIX in the early 1990's, and wrote a driver to decode the signal and synchronise the system.
During the period of debugging it, I could easily tell the time just by listening to the carrier (shifted to audio frequency) - it's easy to decode by ear. It spends most of the minute transmitting what the time will be at the next minute boundary, at 1 bit/second. I didn't decode the fastcode (encoding the date/time quickly in the
59th second), but it was subsequently removed from the signal anyway. I did sit and listen to it through the GMT/BST changes - IIRC, it starts sending a warning bit for an hour beforehand that the clocks are about to change.
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