[time-nuts] VLF time is not dead :-)

Poul-Henning Kamp phk at phk.freebsd.dk
Mon Oct 18 10:26:09 EDT 2004

I found some time to play with my Software Defined Radio VLF receiver
again and have done a little bit of tracking of VLF carrier frequencies:


The Y-axis is seconds, the X-axis are seconds.

It's a bit hard to see the legend, so:

	Red:  RBU 66.666 kHz

	Green: DR LW broadcasting 243 kHz
	       (20 miles away, Rb reference not calibrated)
	Blue: DCF77 77.5 kHz.

	Purple: MSF 60.0k kHz (from the UK, not the US transmitter!)

	Cyan: HBG 75.0 kHz 

The receiver is homegrown:  A loop antenna, an amplifier and an A/D
card in a computer.  The program generates a reference sine/cosine
frequency for the carrier mixes with the a/d samples and averages
over a second.  Sample-rate is 1MHz, 12 bits.  CPU is 560MHz P3.

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.

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