All kinds of things too precious not to share, in short articles. Constantly under construction or destruction. Note that code snippets are usually working minimum examples (often stripped of extra features). If you plan to use and of the code for anything serious, you may want to contact me. It's likely that I can provide you with some updates and good (?) advice. fabian@fkurz.net
Fabian Kurz → Ham Radio → Stuff
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On the CW Ops mailing list, Tim/N3QE started a discussion titled Measuring "nearness" of callsigns in Morse Code space?.
[...] Are there any measures for "code space" difference between callsigns in Morse code? For example, "different by only one element" (nothing<->dit<->dash) would be one possible measure. Most of these would change the length of the callsign but if the change happened at the beginning or the end then you might not notice that something was missing. Another possible measure would be "different by bit elements but same in length". For example if there's a deep fade in the middle of a "T" then it sounds like an "I". Or a longer fade in the middle of a "O" could make it sound like two T's "T T". Super Check Partial does callsign nearness in alphabet space, not morse-space. And I'm thinking that measuring the difference in morse-space might be more relevant. Any ideas or brainstorming? Tim N3QE
My little contribution to this is a PHP script which calculates the Levenshtein distance of callsigns in Morse "samples":
> Any ideas or brainstorming? the Levenshtein distance can be used for this. It's a metric to measure the difference between two strings. However applying it directly to callsign letters would only give a very approximate measure of similarity when we're concerned about Morse code. Using Dits and Dahs instead of letters already brings us closer, e.g. -.- --... ... ...- K7SV -.- --... ... ... K7SS only has a distance of 1 whereas for example K7SQ has a much greater distance. Even better, we break down the code into time samples which would then give a reasonably small error distance for errors where two dits are merged into a dash, like K7SV <-> K7AV. --- - --- --- --- - - - - - - - - - --- K7SV --- - --- --- --- - - - - --- - - - --- K7AV I put this to the test with a small PHP script which can be found here: http://fkurz.net/ham/stuff/morsedistance.php?callsign=K7SV You can enter any callsign and it will be tested against all calls of the current MASTER.SCP file (38k callsigns). Hovering over a callsign visualises the difference. It only shows the callsigns up to a Levenshtein distance of up to 10, but you will see that really similar calls are usually not found beyond a distance of 4. 73 Fabian, DJ1YFK P.S.: The source code is available and linked from the page.
Added: 06-Dec-2018. Last modified: 06-Dec-2018.