Windows PC users now have the option to try yet another weak signal digital mode. Called V4, it is described as "a robust, easy to use, keyboard sound card mode that would fit into the narrow digital segments of our HF bands." The mode is 200Hz wide and capable of sending text at 40 - 60 words per minute.
Do we need yet another keyboard digital mode? Although PSK31 is very popular and very narrow, performance deteriorates under conditions of multipath reception (such as in NVIS propagation) or when the ionosphere is disturbed (polar paths during periods of auroral activity) while RTTY, though also popular, is archaic, inefficient and successful only by brute force methods (a big amplifier and a beam.) More robust FSK modes such as MFSK, Olivia, Thor and DominoEX perform better but are much wider which can be a barrier to use. V4 uses the same robust modulation scheme as WINMOR but has been optimized for use as a keyboard chat mode. A detailed protocol description can be found here and the software can be obtained after joining the V4 Protocol Yahoo Group.
I have only just been admitted to the group so I have some reading to catch up on and it will be a few days before I can find the time to try V4 for myself. However I am quite interested in this mode which seems to have been developed by licensed hams keeping in mind the need for responsible band use (so no 2.2kHz wide signals!) and with all the details being published and open. The software modem has been implemented as a standalone TNC that can be interfaced with other applications such as my own program KComm which is also interesting to me. So I think you can expect to hear more about the V4 Protocol in this blog in the weeks to come.