You'll probably find JT65C is needed on the UHF bands, 432 to 2.3GHz for example, to allwo for teh frequency spreading Doppler - abnd certainly for EME for which it was designed.
Conversely, at LF, 137 / 503kHz, teh A varient is satisfactory and only consumes half teh bandwidth. Andy www.g4jnt.com --- In digitalradio@yahoogroups.com, "Andrew O'Brien" <k3uka...@...> wrote: > > 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. >
