[time-nuts] WWVB BPSK Receiver Project? (fwd)

[Bob Camp]

Hi

One assumption is that you will indeed be capturing / averaging for several
days. I'd include some sort of model for sunrise / sunset shifts (might be
just "ignore for the next hour"). 
Another assumption is that your local reference is close enough and stable
enough to make a multi day average meaningful. 

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Poul-Henning Kamp
Sent: Friday, March 16, 2012 9:03 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] WWVB BPSK Receiver Project? (fwd)

In message <B8FA03DC1DD84A588A317B314A6FCB7B at vectron.com>, "Bob Camp"
writes:

>Could you generate a "lead" and a "lag" estimate of the signal (in addition
>to your "center") and integrate against each of them on the fly? If so you
>would need a *lot* less memory. I seem to recall you tried something like
>this on the one of the Loran receivers. 

The reason to use the lead/center/lag model, is that you have a moving
signal you need to track, but for timenuts purposes the signal is not
going to move more than a few microseconds over an hour, so it is
probably a better strategy to just average the heck out of the signal.

It is not even clear to me that the phase-coding helps frequency
reception at all, I tried it with the very strong phase-coding of
DCF77 and there was no statistical significance relative to heavy
duty carrier averaging.

But it clearly helps a lot with phase-determination, and for that
lead/center/lag is the way to go, but you may still want to average
for a minute, then resolve the phase using the phase-modulation,
rather than run it in real-time.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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