Abstract :
The paper discusses the problem of covering the United Kingdom with television service in the frequency band between 41 and 68 Mc/s. It is proposed to use five high-power transmitters, with a further extension of five low-power transmitters to cover other populated areas outside the range of the main transmitters; this will necessitate common-channel working. An accurate forecast of the service of a transmitter using very high frequencies can be obtained only by erecting a test transmitter on the proposed site and measuring the field strength in the required area. The aerial used for these tests is attached to a balloon which replaces the mast required at the final site. Such tests were carried out in the North of England, Scotland, Wales and the West of England; the results are shown, and the reasons for the final choice of sites are given. Estimated figures for the population covered are also given. The effect of raising the transmitter aerial on the received signal is very dependent on the ground profile between transmitter and receiver.Height/gain curves are shown for various transmitter sites. Experiments were made at two sites, to observe the effect of the reradiation from structures near the transmitter sites which might have given rise to ghost images on a television service. Short-duration pulses were radiated from the test transmitter, and the delay time and amplitude of the echoes were measured. The echoes observed were caused by obstacles, such as buildings, close to the receiving point; those due to structures near the transmitter site were negligible.
