>I'm still on rc1 but have captured two .wav files of false decodes without any >"aX?" marking. >First on 6m and second on 4m. Both captured from very silent band, no many >other stations.
Hi All, In Saku's example false decodes are due to noise. Decoder can detect even an empty band synchronization patters with a probability that is not very low and continues decoding and error correction. You could continue error correction actions 'forever', but at some point you 'give up' and assume you got a message. At that point it may or may not be a real one. In the message there are also error detection bits and those are used to filter out most of the fake/false messages. It is always a compromise how many bit are used for error detection and how many for information. In order to get needed information send in a small number of bits an efficient source coding is used. An interesting side effect of that are those good looking false decode messages as almost any random bit combination can be a 'valid' message. Just a single bit error in a proper place adds e.g. /R to the decoded message. AP decoding increases probability that a false decode contains your call sign, but that is the cost of getting a marginal QSO completed. As Bill noted the above is valid also in crowded bands due to QRM, QRN, QSB, partial message length and is not limited to low signal levels. Personally I prefer to get more false decodes and more marginal decodes than less of both. The 'help tools' for detecting potential false decodes could be added into a companion program and keep WSJT-X as a clean decoder that present information as got over air interface. The external program could e.g. use different color, font etc. as potential false decode indication. 73, Reino OH3mA PS The above description is at a general level of error correction and detection side effects. _______________________________________________ wsjt-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/wsjt-devel
