-------- In message <2126b261-3e4e-46d4-9181-1fb368244...@n1k.org>, Bob Camp writes:
>One *could* make a WWVB “new modulation” receiver with some sort >of MCU demo board and a handful of parts. It would be fine for a basement >lab / learning sort of project. With reasonable OCXO as timebase, it would do much more than that. SRS sold the SR700 Loran receiver as a "Cesium replacement". >the longer you wait to start that project, the better a board you will have >as the base of the project. Current boards are more than capable of this, a 12 ADC at 1MSPS is plenty. >How many people want to spend more than a year on that sort of thing Unless you're a total programming beginner, you will have carrier lock in a week: * Configure ADC for 1MSPS * Interrupt routine: exponentially average the samples into a 50[1] bucket circular buffer * Control-Loop (not time-critical): * Multiply 50 buckets with synthetic sine/cos function, * Average the 2x50 results to get I/Q phase signal. * Feed phase into PLL to steer OCXO. * Bonus: Decode timegram. I did that with Loran-C, which is a *much* harder signal, I did it 8 years ago, and I did it in two weeks. Poul-Henning [1] If you use a platform with enough memory, for instance a BBB, use a one million (=full second) buffer instead, you will be able to pull any and all VLF signals out of it. For instance the US navy runs a couple of stations with frequency stability comparable to WWV. On a BBB you could even add a FRI length buffer also, to receive the Wildwood Loran-C. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@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@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
