[time-nuts] WWVB d-psk-r down conversion method...

Burt I. Weiner biwa at att.net
Tue Sep 23 12:16:11 EDT 2014


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

>From: Charles Steinmetz <csteinmetz at yandex.com>
>Subject: Re: [time-nuts] WWVB d-psk-r down conversion method
>Paul wrote:
> >The goal is to remove the psk so the old phase tracking receivers can work.
>Yes, I understand that.  But you want them to work like they
>originally did, with the disciplined oscillator in the phase tracking
>receiver phase-locked to the WWVB carrier (or else you may as well
>just ignore WWVB entirely and generate your own 60kHz carrier).  Once
>you add an LO/BFO, the signal you end up with is NOT locked to the
>WWVB carrier -- it is locked to some frequency that is determined by
>both WWVB and the LO/BFO (whch means, it is only as accurate and
>stable as the LO/BFO).  So the whole benefit of receiving WWVB in the
>first place is lost.  [In the special case of a TRF receiver, with no
>LO/BFO, the signal will remain locked to WWVB.]
> >Whats good about this as I just typed to Bob the signal is slow and easy to
> >work on.
> > From what I have seen the phase tracking receivers have a fairly long time
> >constant. So the fact that the phase detect and flip occurs 1/10 of a
> >second later should not have any effect on these radios.
>It's got nothing to do with how fast or slow the signal you end up
>with is, or how easy it is to work on.  If the frequency and phase of
>that signal are not uniquely dependent on the WWVB carrier frequency
>and phase, then the oscillator you discipline will not be disciplined
>to the precision of WWVB -- it will be disciplined to no better than
>your own LO/BFO.  [Also note that the phase flips at one second
>intervals no matter what frequency you translate it to -- that is not
>a unique feature of the 100Hz recovered carrier.]
>As Alex pointed out, you could in theory use a LO/BFO that is,
>itself, derived from the disciplined oscillator, and in which the
>loops will not lock unless the IF and LO have the correct
>values.  But, as Alex also points out, such a scheme will have about
>the same complexity as a Costas loop.  The Tracor itself uses a crude
>variant of this strategy, in which the LO is guided "huff-n-puff"
>style in steps of 1/100 of a cycle, some steps above and some below
>the correct frequency.  But when you are starting with a signal that
>is already orders of magnitude less stable than a GPS signal, it is
>just rude to throw away even more stability with that sort of
>approximation.  Furthermore, all of this would need to happen outside
>of the old-school phase tracking receiver, so you'd end up building
>your own external phase tracking receiver just to run the old phase
>tracking receiver.
>Best regards,

Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California  U.S.A.
biwa at att.net

More information about the time-nuts mailing list