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I'd like to get some recordings of typical receiver audio output of HF CW transmissions.

I'd like to both train my mental copying capabilities and look into improved automatic (software) CW transcribers; hence, typical, humanly induced symbol rate changes are of special interest. Ideally, there'd be a few recordings of similar (the same?) transmission at different RX SNRs.

Instead of the audio recording, I'd also take "raw" I/Q, IF or direct sampling recordings.

As correctly pointed out in the comments: I'm a total novice when it comes to digesting CW. Which means that I can't tell a well-keyed transmission from a lesser one; I've found it vastly helpful to have reference signals in the past, so I'm really asking for recordings of transmissions of "known" quality, not an information on how to make my own recording (which I can't classify myself).

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    $\begingroup$ @MarcusMüller I find that I can copy "well-keyed" CW (aka Morse Code) up to about 35 wpm. But, sloppy code slows me down considerably, maybe even below 20 wpm. So, I have my own sort of measure of good quality code -- I can copy it easily. Usually a measure of good code is whether you can copy it easily so that is the best way to determine "well-keyed" code in my opinion. $\endgroup$ – K7PEH Jul 8 '16 at 4:50
  • $\begingroup$ Sounds like you want straight key night on January 1. $\endgroup$ – Phil Frost - W8II Jun 21 '17 at 13:28
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On the computer-assisted side of things, AG1LE has a nice write-up on applying machine learning to the complex task of adaptive CW recognition (adaptive for the purposes of HF reception).

On the same site, the author talks about the Morse Learning Machine Challenge, in which another participant used their own curated recordings to teach the system the difference between signal and noise as well as interruptions and human pauses. The GitHub repository for the challenge contains these training file (under ./acidtobi/trainingfiles/) as well as the source.

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I found a lot of MP3 files at the ARRL:

http://www.arrl.org/code-practice-files

They are pages from QST magazine, so the text is also available. There are multiple files for each text sent at various rates.

If you have an HF receiver they also transmit code practice sessions. The schedule and frequencies are at: http://www.arrl.org/w1aw-operating-schedule

Glenn

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Check out websdr.org. There you'll be able to 'tune in' with a web-based java application to stations all over the world. Live. Typically you'll find CW at the bottom of the bands (e.g. around 7.000MHz - 7.030MHz).

These days you probably won't find a lot of (manual) straight keyed CW, it's pretty much all nice and clean (microcontroller based) keyer output.

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Try this:

http://w3ttt.radiostream321.com/

I have set up a streaming internet station that reads the news feed from Google, removes all those pesky HTML tags, and sends the text in morse code. It is great for practice, for two great reasons: 1) because it is news and interesting. I fantasize that I am a shipboard radio operator in the 1930's. And 2) it tends to repeat words or phrases, which is good because if you missed something, you get it a few more times, and then get better at it.

And 12 words per minute is a nice speed - not too slow - but relatively easy to achieve. I think that 12 wpm should be the default CW speed on ham bands.

W3TTT

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