In message 38553AAD-ECC6-4AF8-90B3-42BBEC366CA6@msys.ch, Marc Balmer writes:

Go SDR.

There are ARM7 chips now that have sufficient ADC quality  to do the
job.

See for instance: http://phk.freebsd.dk/AducLoran

Poul-Henning

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Never attribute to malice what can adequately be explained by incompetence.

Am 22.06.2009 um 10:14 schrieb Poul-Henning Kamp:

Ok, thanks.  I happen to have some Overp Earth boards, OMAP 3503
Application Processor with ARM Cortex-A8 CPU, do you think these
will handle the job? (runnin at 600 MHz).  They say it makes up 1200
dhrytsone mips

(www.gumstix.com)

Thanks for the pointer, I already found that, nice work!

• Marc

In message 70D1E333-26C4-4068-BFAC-30D689BBF3D1@msys.ch, Marc Balmer writes:

It's more a matter of what their ADC can do...

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@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.

Am 22.06.2009 um 11:46 schrieb Poul-Henning Kamp:

unfortunately it's "only" a TI TPS65950 which has only an audio codec,
the ADC doing 48kHz max.

In message 0587CB86-96EF-4660-9FBE-8C1D1FDFBAFB@msys.ch, Marc Balmer writes:

That's still usable, you could for instance use a "DRM" frontend
like the "pappradio"

There are some links here:

http://www.drmradio.dk/Byggesaet og konvertere-da.htm

Poul-Henning

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@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.

Hi Marc:

The SDR-IQ has the ability to record everything between 500 Hz and 190 kHz when
used with a fast enough PC.  This is the best of the SDR series for use below
200 kHz.
It can be used with SpectraVue or Winrad.
Works with I2PHD WINRAD, SM5BSZ LINRAD, HOKA and DRM software.  See:
http://www.rfspace.com/SDR-IQ.html
http://groups.yahoo.com/group/SDR-IQ/

Have Fun,

Brooke Clarke
http://www.prc68.com

Marc Balmer wrote:

Am 22.06.2009 um 16:18 schrieb Brooke Clarke:

very nice, indeed, although it does not fit my definition of cheap.

but then I'd like to get one of these, are the specs and docs open?
I am not using Windows but rather Unix (BSD)

In message 4A3F9299.9080505@pacific.net, Brooke Clarke writes:

I have looked at that earlier, but it does not look like it is feasible
to lock its clock to an atomic reference :-/

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@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.

200kHz is a bit tricky for the top end.. That probably puts the standard music recording A/D out of the picture (although they have very high performance A/Ds in them, and because of large production volume, they're relatively inexpensive).

Almost any PC these days has enough processor to take a 400 ksps stream of samples and filter/decimate it.
Maybe the boards from the HPSDR folks might serve?

Do you need continuous stream of samples? One of the eval boards for high performance A/Ds with a USB might work for you, but last time I checked, they were more oriented to "capture a buffer, then analyze" sorts of approaches.

Your best long range approach might be to use a high quality A/D with a small FPGA behind it that implements a digital down converter, feeding the (lower rate after downconversion/filtering) samples through USB to an application like DL4YHF's spectrum lab.  DL4YHF is very interested in VLF receiving, and he might have good ideas on inexpensive approaches.
http://freenet-homepage.de/dl4yhf/spectra1.html