Automatic measurement of telegraphy speed - finding approximate value from probability curve and refining by comparison with signal

摘要

The speed of a telegraphy signal is measured by determining the times between transitions from one level to the other and digitising them. The times are first accumulated in a store to build up a probability distribution and the shortest time with significant probability, e.g. 10%, is taken as the step time. Deviations of transition times from multiples of the step time are then summed - sum A, and the multiples themselves are summed - sum B. During the summation, the signal is tested to exclude interference pulses. The ratio A/B is then added to the step time. This is repeated until A/B changes sign at least twice. The speed is then computed as the reciprocal of the step time. The method can be used for automatic measurement by a computer and is suitable for speeds up to 100kBd.