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 _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
