While addressing an ARRL LOTW uploading issue with JT65 modes, I began to be intrigued about B and C that I have never tried . Here is an old 2004 explanation from Joe Taylor. Interesting ,at that time , that he was suggesting JT65B be the standard
Mode Spacing Total BW ------------------------- JT65A 2.7 Hz 177.6 Hz JT65B 5.4 355.3 JT65C 10.8 710.6 Note that JT65A is identical to the original JT65. If you want to work people who have not yet upgraded to v4.3.3, be sure to select mode JT65A. Otherwise, be sure to use the same mode that your QSO partner is using. Cross-mode contacts will not work. JT65B should be nearly as sensitive as JT65A, and it will be twice as forgiving of frequency instabilities. On balance, with existing "stock" radios, JT65B will probably be better than JT65A. JT65C is less sensitive by a small amount, perhaps 1 dB, but will be even more lenient on stability issues. By all means experiment with the different submodes, and be sure to let me know your conclusions about them! I am presently inclined to recommend that JT65B should become the "standard" JT65 mode. If this tentative conclusion holds up, future versions of the program may no longer support the A and C modes.
