[time-nuts] WWVB d-psk-r down conversion method...
paulswedb at gmail.com
Tue Sep 23 13:42:41 EDT 2014
Goal of teh d-psk-r is to correct the phase shift so any of the radios will
work without modification. Be it time or frequency.
However for those with just a need for time like the spectracoms, the
remodulator circuit does that job very well and has been in use for over
Darn simple. It was updated about march of this year with a discussion on
various wwvb atomic clock modules that will work.
The d-psk-r will correct the phase issue and allow the Fluke 207 tracor
599, HP 117 etc to work a byproduct of that method is that it allows the
time units to also work.
I have released some analog d-psk-r approaches and even a direct hack into
the spectracom phase receivers. (I hate internal hacks. But if you only had
one receiver it makes a lot of sense.) Have shared all of that over time
with Time-Nuts. Some folks closer to wwvb then me have used the frequency
doubling method. Lucky them all manners of that method fail pretty badly
over time on the East Coast.
Alex is right as I learned the really narrow Xtals actually loose the
signal for numbers of cycles at the phase flip since they are 60 Khz +- a
few Hertz. It gaps actually.
Make up a remodulator and you are back in business with the 8170. Its great
to see those panalplex displays correctly running again.
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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