[time-nuts] WWVB d-psk-r down conversion method...
mike at mikeharpe.com
Tue Sep 23 13:43:55 EDT 2014
According to the NIST documentation there were a couple of motivations...
1. BPSK is easier to receive in high noise environments so they say.
2. The new format supports sending additional information in addition to
the time of day. The other messages are interleaved into each minute and
they take a long time to receive.
On Tue, Sep 23, 2014 at 1:11 PM, Alexander Pummer <alexpcs at ieee.org> 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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