An investigation of wireless waves arriving from the upper atmosphere

In a previous paper (1) the authors drew attention to the desirability of obtaining some conclusive experimental evidence as to the actual path of travel of wireless waves between the transmitter and receiver. According to modern theory the upper portion of the earth’s atmosphere acts in the nature of a deflecting medium, from which some or all of the energy reaching it from the transmitter is returned to the earth’s surface, these downcoming waves having a variable plane of polarisation. It was thought to be possible to demonstrate the presence or absence of such downcoming waves by making measurements at the earth’s surface of the directions of the forces in the resultant waves received. The method adopted for the determination of the direction of the electric force in waves from near-by transmitters gave a means of measuring the effective conductivity of the earth’s surface for wireless frequencies. This conductivity was found to be of such a high value that on theoretical grounds it was shown that the possibility of distinguishing between downcoming waves and horizontally propagated waves by directional measurements of the resultant forces would be very difficult on the medium and longer wave-lengths employed in commercial wireless communication. This deduction was confirmed by measurements carried out during 1924 at the Slough station of the Radio Research Board. Operating on transmissions whose wave-lengths ranged from 2,600 to 9,000 metres and under conditions where it was known that the usual phenomena (including night effects) of long-distance wireless transmission were present, the results showed that the directions of the resultant electric and magnetic forces in the received waves provided no definite evidence for or against the existence of downcoming waves. The apparatus originally set up at Slough has been in constant use from October, 1924, until December, 1925, for similar measurements. The transmissions from Leafield on 12,400 metres and Nantes on 9,000 metres have been kept under constant observation and occasional experiments have been carried out on other transmitting stations using wave-lengths about 5,000 metres. The results obtained have fully confirmed the deductions previously made.