[time-nuts] WWVB d-psk-r down conversion method...
brooke at pacific.net
Tue Sep 23 16:08:35 EDT 2014
Sometime in the future there will be chips that will decode the new signals (note the "s" on the end of that last
word). There are a number of frame times the longest one of which takes 17 minutes and is transmitted only once per
day. This format offers 23 dB modulation gain compared to the 1 minute time frame transmission that the current clocks
use. There are a total of 5 different modulation formats that will be transmitted over different time frames. In the
end everyone should have a clock with more frequent updates (on the West coast I might need to wait overnight for a
clock to sync after a battery change) and more accuracy.
Alexander Pummer wrote:
> there is an interesting side effect with that phase modulation: in case the crystal filter is "narrow enough" --to use
> for the old AM format-- the phase change creates an additional AM modulation, if you take in consideration that effect
> by the decoding the modulation, you could recover the time information "despite" of the presence of the PSK.....
> Question: as fare as I am informed there is no chip/system available to correctly decode the new signal form, what was
> the purpose of the whole modulation format change?
> The old AM format was happy with cca 200Hz bandwidth to recover the time information, which was utilized in many
> professional receivers, which used a crystal filter for 60kHz, for the PSK format the required bandwidth is at least
> five times wider, so crystal filter would be problematic and much more costly, the higher required bandwidth brings
> also more noise ....actually where is the advantage of the new modulation scheme?
> On 9/23/2014 9:16 AM, Burt I. Weiner wrote:
>> If I recall correctly, the original point of the d-psk-r was to cause the clocks to again read the correct time, not
>> maintain their use as a frequency standard. I have a Symmetricom 8170 that I used to use only as a clock to tell the
>> time of day. Since WWVB's addition of the PSK coding, it's only good to watch the pretty blinken lights.
>> Burt, K6OQK
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