The hash function used in wspr is 15 bits wide, i.e., there can be 32,768 values. This may seem like a lot, but the "birthday paradox" says that the probability of a collision grows faster than you might expect as the set size grows. It comes from the fact that you only need ~23 people to have a 50% probability that two of them have the same birthday.
A very rough approximation is that the probability of a collision is 1/2 when the set size is equal to the square root of the hash size. For 15 bits, that's about 180. My hashtable.txt for 40m currently has 353 entries. Has anyone seen a collision in practice? If one occurs, the most recent duplicate entry is most likely the correct one. Requiring a match in the first 4 characters of the grid square would also seem to greatly reduce the problem. Phil _______________________________________________ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
