[time-nuts] WWVB PM Time Questions

[Bob kb8tq]

Hi

Backing up a bit …..

The WWVB modulation is *very* predictable. Once you have lock, 
you can guess just about every phase reversal you will see. If you 
have an “approximate lock” ( = a time pre-load that is within a few
seconds) you can guess a lot of them. (There were a few aux data bits 
in the stream last time I looked).

In the case of the pre-load, you still need to get your local stream
lined up with reality. In all cases, the ionosphere will move things 
enough that some modest amount of servo would be needed.

The point of this being that you *could* pre-flip the data before it
went into a buffer. That way the buffer integration time constant 
could be quite long. 

The main penalty is a bit of work getting it all locked up in the first
place. If this is a precision timing receiver (as opposed to a wrist
watch) that may not be a problem. 

Bob

> On Jul 30, 2020, at 11:45 PM, rcbuck at atcelectronics.com wrote:
> 
> Paul,
> 
> I wasn't talking about putting the d-psk-r software on the Blue Pill
> board. The d-psk-r software will be on the Arduino board.
> 
> What I was thinking of doing was putting a single NEMA message on the
> Blue Pill board. Then connect the UART transmit line to the Arduino in
> place of the GPS UART line. That way I could send the same NEMA message
> without having it change every minute. I would count 60 (or maybe 62)
> pps coming from the GPS and I would know the Arduino was ready for the
> next NEMA message.
> 
> Initially I will use the GPS UART transmit line to confirm the
> Arduino/GPS combo works. Then play with sending my own NEMA GPRMC
> message from the Blue Pill board.
> 
> 
> It appears your software simply reads the TX buffer of the GPS until it
> is empty once per minute and then proceeds to parse the NEMA time/date
> information out one bit per second. However, the La Crosse Ultratomic
> clock would not work with this data stream since you are stripping the
> phase reversals out. Is that correct?
> 
> I want to extract the time information only. So I would feed the 60 kHz
> sine wave into the preamp wire on the flipper board. Is that correct?
> 
> Ray,
> AB7HE
> 
> -------- Original Message --------
> Subject: Re: [time-nuts] WWVB PM Time Questions
> From: paul swed <paulswedb at gmail.com>
> Date: Thu, July 30, 2020 5:14 pm
> To: Discussion of precise time and frequency measurement
> <time-nuts at lists.febo.com>
> 
> Ray
> Are you speaking to the d-psk-r software? Its quite a bit more involved
> than what you mentioned. Its in the coding sequence. But could it be put
> on
> a bluepill absolutely. Its worked on all of the arduinos we have tried.
> The
> other thing is that by feeding a 60 KHz CW signal into the d-psk-r
> modulator/flipper it turns the signal into a wwvb bpsk signal. No AM
> modulation. But for bench testing its a noise free signal.
> But I am interested in the approach you are trying to develop that I
> guess
> might be a SDR solution. Good luck looking forward to your success.
> Regards
> Paul.
> 
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