[time-nuts] WWVB Measurements using DSP recovery

[Poul-Henning Kamp]

In message <4D9129D8.4060609 at comcast.net>, Greg Broburg writes:

>Can you show a circuit of what you have done?

Basically I have a 20MSPS PCI card in a PC and do it all in
software.

I did use similar principles to implement a LORAN-C receiver
in a aduc7216 (http://phk.freebsd.dk/AducLoran/) but that is
passe for US people now.

>Would you recommend the 7200 again or something
>else that is better suited?

The most user friendly way to do it, would be to have a small FPGA
which takes data from the ADC and averages it into a small piece
of multiplext or dual port RAM, and a microcontroller (ARM ?) on
the other port, doing all the high level stuff.

That way there is no real-time component to deal with in the
programming, and anybody should be able to play with the code.

The alternative is to use a DSP to read the ADC, do the
averaging and perform the high level functions.  That would
be a lot harder to program for most people.

The ADC could be 16 bits, and run directly from a house standard
of 5 or 10 MHz (looks like that would cost $4 from analog.com, isn't
this future amazing ?)

Add a high resolution DAC for steering OCXO's and a serial port
or USB interface and we're done...

-- 
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.