Dear Joe, dear members of the WSJT Development Team, I am Yousuf AL Balushi, A41UX, from Oman. I write amateur-radio apps for iPhone and Android under the name Unixeer, and I am writing as a courtesy before I publish one of them.
Ham Signaling is a digital-modes app for iPhone and Android. Its first release, not yet published, will include JTTY as a keyboard mode beside RTTY, PSK and Olivia, marked "Experimental". I would like you to hear it from me first, and I have two questions. How it was built: • The JTTY codec is jtty_lib from the JTTYAF project (MIT licence, github.com/patrickrb/JTTYAF<http://github.com/patrickrb/JTTYAF>), used unmodified. A second independent implementation, jtty-cuf (MIT, by OH3CUF), is used only inside our tests, as a cross-check. • We read your published documentation — the User Guide, the release notes, and the JTTY description files published with WSJT-X (jtty_source_encoding.txt and jtty_design.md) — but no WSJT-X program code, and we checked the result against your released programs as black boxes. • With WSJT-X 3.3.0-beta2, rjtty decodes the app's transmissions exactly, and the app decodes the output of sjtty, including with the fading models. Your sample recording 260807_134110.wav decodes as "RAN ALL NIGHT ON BAND NOISE - NO FALSE DECODES!". • A message is at most 80 characters; the app refuses a longer one rather than cutting it. • The app names WSJT-X as the origin of JTTY in its list of modes and in its manual, and uses the name only to say where the mode comes from. If you would like that worded differently, please tell me and I will change it. My two questions: 1. Do you welcome independent implementations of JTTY, and on which terms? For FT4 and FT8 your 2020 QEX paper sets the terms out. We have found nothing comparable for JTTY yet, and we would like to follow whatever you ask. 2. Would you consider completing section 20.3.3 of the User Guide, which today reads "(… more to be added …)"? Independent implementers take the sync word, the generator polynomials, the CRC and the modulation details from third-party write-ups. An official description would help keep every implementation compatible as the mode develops. And a small one: if the over-the-air format may still change before the general release, is wsjt-devel the right place to watch for it? Thank you for JTTY, and for everything the WSJT team has given the hobby. 73, de Yousuf AL Balushi / A41UX / 73
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