EMRFD Message Archive 2593

Message Date From Subject
2593 2009-01-14 10:41:34 timshoppa Computer or DSP broadband demodulation (e.g. CW Skimmer)
I got to see CW Skimmer in action last November in the CQ WW CW
contest. It's an astonishing program; it is not a single CW decoder,
but can simultaneously track and decode dozens of different CW
signals on a waterfall-type display. No, it's not as good as a
trained ear for picking out weak signals from QRN or QRM, but it is
remarkably useful in finding contest multipliers in very crowded

I saw it hooked to a fancy-pants Japanese rig but evidently it works
just fine with extremely simple I/Q receivers like the SoftRock or
those in EMRFD.

It also works as a broadband I/Q recorder to some extent too. That's
an intriguing idea for say SWL'ing.

Ten or fifteen years ago I saw some very expensive spook technology
that did similar stuff, but to tell you the truth it wasn't as good
as CW skimmer :-). It's astonishing that today a $500 PC and any I/Q
receiver can do this stuff. I spent decades using old simple or
homebrew radios, and I had friends with fancy-pants expensive radios
that I thought weren't nearly as fun, but CW Skimmer just transcends
all that.

This sort of technology with some smart software could produce a
robo-station contest based entirely out of Frankensteined Softrock-
type I/Q receivers that could do astounding stuff.

Here we usually talk about the hardware end, but are there any open
source multi-signal I/Q CW decoders out there? I really have a
hankering to "look under the hood" and learn the software-side
signal processing techniques that produces the magic decoding. Maybe
even tweak it. I don't want to replace CW Skimmer but want to know
at least some of how it works its magic.