Details

Slide rule for the calculation of ionospheric absorption loss and of maximum usable frequencies in the lower ionosphere, developed by Les Barclay. Conversion of the manual calculation process into a slide rule was reported in an article titled, 'slide rule for the calculation of ionospheric absorption loss and of maximum usable frequencies in the lower ionosphere', by L W Barclay, 'proceedings of the IEE', vol.110, 1963, pp 1523-1527. The Marconi Company manufactured a prototype of the slide rule and then had 100 manufactured, mostly for sale. The slide rule was used for predictions by Marconi, the Armed Services, BOAC and others until a computer based procedure was later developed. Prior to the development of this slide rule, in the post-war years, predictions of HF propagation (which provided almost the only means of long distance communication before the days of satellites and wide-band cables) were done manually with graphs, nomograms and 'normal' slide rules. The method most commonly used in the west was that given in the US National Bureau of Standards publication no.462, 1948. In 1959, W R (Roy) Piggott of the DSIR Radio Research Station prepared an improved method, published in DSIR Special Report no.27 (not widely taken up due to the availablility of circular no.462). Marconi Research did adopt the 'improved method' when Les Barclay restarted the prediction service after he joined Marconi Research. [Descriptive information provided by Les Barclay] [Digital image available]