>I note the new release of FL-Digi does not list PSK31 or 63 under > NBEMS modes. I realize that Dave , Skip, and others never really > intended NBEMS to have much use on HF , hence PSK250/125, but was > wondering why the option of slower PSK modes has been removed.
Andy, PSK31 and PSK63 are still there for use in QSO's but neither mode is as good as MFSK16 or MFSK32, or our new Thor modes, for ARQ messaging when high static conditions on 80m or 40m exist, which is most of the time in the summer or before and after a hurricane, so MFSK16 or MFSK32, wider, but the same speeds as PSK31 and PSK63, are recommended for NBEMS messaging over PSK31 and PSK63. The MFSK16 and MFSK32 modes are not your grandmother's MFSK modes, but have been made more robust under static conditions on HF when PSK63 and PSK31 get pulled off frequency by the AFC if there is a static crash between ARQ transmissions. It was a tough decision not to include PSK63 in the recommended NBEMS mode list, but the job of NBEMS is to accomplish the most reliable messaging for any given speed, and the modified MFSK modes are simply more reliable, although they are wider. For VHF messaging, PSK31 and PSK63 lose out again over DominoEx11 and DominoEx22 at the same speed, because many VHF multimode transceivers have no TCXO and drift too much to maintain tuning on 2 meters during an ARQ transfer, whereas DominoEx has a wide tolerance to mistuning or drift, such that no AFC is needed and provides a lower minimum S/N than the PSK modes at the same speed. PSK31 and PSK63 are easier to recongnize among the background noise on VHF, so it is often best to establish tuning with PSK41 or PSK63, check to see if there is no adjacent frequency activity, and then switch to DominoEx for the ARQ transfer. The popular IC-746Pro, for example, drifts 100 Hz between receiving and start of transmitting, unless a TCXO is added, causing the loss of the first few characters or words on PSK63, so I have switched our 2 meter digital net from PSK63 to DominoEx. 73, Skip KH6TY NBEMS Development Team
