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

paul swed paulswedb at gmail.com
Mon Sep 22 20:03:48 EDT 2014

The goal is to remove the psk so the old phase tracking receivers can work.
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.

On Mon, Sep 22, 2014 at 7:56 PM, Charles Steinmetz <csteinmetz at yandex.com>

> Paul wrote:
>  One of the methods suggested for working with the wwvb psk is down
>> converting to a lower frequency. When experimenting with NAA I had built a
>> 24 Khz receiver that down converted that signal to a 100 Hz base band.
>> It was a minor effort to shift it to 60 Khz by changing the LO.
>>    *   *   *
>> for 100 Hz the LO must be at 60.1 or 59.9 Khz. Or synthesize it etc.
>>    *   *   *
>> Not sure there is a real need to lock the LO at all.
> I'm not sure I understand how this helps.
> I thought the point of removing the PSK was to reconstitute a version of
> the original unmodulated carrier, so it can be used to discipline an
> oscillator at some convenient frequency (the PSK needs to be removed
> because it upsets the PLL phase detector).  That works (in theory) with a
> TRF receiver, because the received carrier IS the tx carrier that is locked
> to a standard at the transmitter (modified by the propagation delay and
> delay variation, and then by doubling/squaring).  But once you convert the
> received frequency by using a LO (or BFO, whichever you want to call it),
> the recovered carrier frequency is dependent on BOTH the tx frequency AND
> the LO/BFO frequency.  You have lost the link to the tx frequency standard.
> Am I misunderstanding the goal of the exercise?
> Best regards,
> Charles
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