[time-nuts] Looking for info about first true radio controlled clock

Bob Camp lists at rtty.us
Wed Feb 23 12:42:15 UTC 2011


On Feb 22, 2011, at 11:53 PM, jimlux wrote:

> On 2/22/11 12:12 PM, Magnus Danielson wrote:
>> Hi Jim!
>> 
>> On 02/22/2011 02:34 PM, jimlux wrote:
>>> On 2/21/11 10:12 PM, Michael Lombardi wrote:
>>>> I'm trying to determine the first product that could automatically
>>>> decode and display a digital time code. Digital time codes were
>>>> added to WWV in 1960 and WWVB in 1965. This was before they were
>>>> added to any satellite signals, or before they were added to LF
>>>> stations in Europe, such as DCF77. Telegraphic time codes, of
>>>> course, were around much earlier.
>>>> 
>>> 
>>> the IRIG standaards started in the late 50s, and I'm pretty sure that
>>> they used time code when recording on instrumentation recorders earlier
>>> than that. You'd record a bunch of analog signals using FM on a
>>> multitrack recorder, and because the playback speed varies and the tape
>>> stretches, you need something to recover actual timing.
>> 
>> The NASA 36 bit time-code seems to pre-date both IRIG and WWV broadcast.
> 
> NASA didn't exist until 1958, but I suspect that there were folks doing time code and it just came along for the ride.


Thus the rather interesting start time for some of the time codes of January 1, 1958 with a roll over modulo 256 or what ever ...


> 
>> 
>> The original WWV broadcast where in fact done in the NASA 36 bit time-code.
>> 
>> "STANDARD FREQUENCY AND TIME SERVICES"
>> http://tf.nist.gov/general/pdf/1746.pdf
>> 
>> I have yeat not found the NASA time code history or for that matter the
>> NASA standard for it.
> 
> funny, now that you mention it.. we use NASA 36 bit in places at work, but, all my stuff uses IRIG in one form or another.
> 
> CCSDS time codes reference NASA 36 bit.. maybe a reference it's in the back of the CCSDS standard.
> 
>> 
>>> the first instrumentation recorders were used in the late 40s or early
>>> 50s
>>> 
>>> there's also a famous spread spectrum system used during WW2 with
>>> identical phono records with random noise, but I think those were sync'd
>>> by hand.
>> 
>> They where synced by hand, but the turn-tables ran on synchronous motors
>> locked to a common frequency broadcast, so the system had an external
>> (common) frequency steering.
>> 
>> Cheers,
>> Magnus
>> 
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> 
> 
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