Re: [Discuss-gnuradio] Decoding Morse code

[Iain Young, G7III]

On 06/03/15 19:19, Mike Markowski wrote:

> A few weeks ago I started learning my way around gnuradio and am making
> progress, but could use advice from experienced users.
>
> I've been making something of an online lab notebook recording my
> efforts in gnuradio at:
>
>    http://udel.edu/~mm/gr/
>
> At the very bottom of that page is a section named "Morse Code Decoder"
> where I show a flowgraph I've come up with.  I can't figure out how to
> take it farther than that, however.  I believe I need to learn how to
> write an out of tree demodulator.  If I'm wrong, maybe someone can give
> me a push in the right direction regarding how to use existing blocks.
> If I'm correct, what would be the best modulator to study - BPSK?
> ("Best," meaning easiest for someone new to gnuradio to understand.)

I would pass this through a threshold block, followed by a float to
char, then out to a file (pipe) or UDP socket.

Then write your own code to take in the stream of 1's and 0's, and
decode the morse that way.

I essentially do this with my SDR radio clocks, but then I'm just
looking for a pulse of 100, 200, or 500msec, but the concept and the
theory are the same. I just used getc() and stdin.

For my purposes I dropped it down to a 1kHz stream of 1's and 0's
(actually by use of a Goertzel filter as I was tuning slightly off for
debug and able to hear it purposes!), but a Rational Re-sampler would
do just as well.

Auto detecting speed can be done - I actually wrote a prototype for use
with the CW ID of the Russian BETA Time Stations, that essentially
took a number of pulse's and gaps, worked out the differences, then
decoded the next set of dits and dahs. To be honest it was pretty
awful, but then I just needed to decode two numbers...


Iain