Propagation tests with micro-rays

A description of propagation tests using wave-lengths down to 18 cm. [see Abstract 1936B02046] across the English Channel. The circuits and reflectors are described in detail, together with the necessary adjustment of the valves and the feeders. The results of extended trials show that communication is possible for at least 80% of the time for wave-lengths of 18, 20 and 29 cm., while combination of at least two wave-lengths provide reliable transmission for more than 90% of the time under comparatively unfavourable conditions. The actual variations of the signal to noise ratio depend on the wave-length and any effects due to the tides appears to be masked by the variation in roughness of the surface of the water. Local variations due to persons or ships passing into the receiving beam are of importance, while the general weather does not appear to have any effect, apart from an increase in fading when the temperature is very high; stability is greater in the morning than in the afternoon.