Charles,
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 <csteinm...@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,
Charles
Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California U.S.A.
b...@att.net
www.biwa.cc
K6OQK
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