In order to help the students cope with the design study that formed the basis of the project Scotia competition (see ibid., vol.15, no.4, p.220-2, 1980), the participants were provided with fairly detailed technical information about UHF television broadcasting. The authors summarise this information which should serve as valuable resource material for teachers of physics, electronics and electrical engineering.

The paper describes the reasoning behind a very small but efficient antenna now being used in several daily services for AM broadcasting on Medium Wave. The design methodology is outlined and there is a plot of the field strength measured for one of the early services in 1992. Not only is the antenna wide band, but it is more efficient than normal monopole antenna, and therefore allows a reduction in power costs when radiating comparable signal strength. B A C K G R O U N D AND DESIGN OBJECTIVEIf the standing waves on a classic half-wave dipole are examined fig.(l), it is very clear that they are neither exactly co-located nor are they exactly synchronized. It is usual to consider the radio wave to be plane (at a long distance from the antenna), as a system of in-phase transverse crossed Electric and Magnetic high frequency sinusoidal oscillations, in geometry at right angles to each other and the direction of travel, Fig. (2). : , Fig (I) standing waves on a halfwave dipole.

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It is shown how the Biot-Savart law arises as a consequence of the Maxwell law D′ ⇀̲ ∇ × H, where time-varying electric fields are produced through charge motion. These ideas provide the continuous source of H away from moving charges, which the term J in Maxwell's 4th equation cannot provide.

The s o l u t i o n is based on a two-term s i n u s o i d a l c u r r e n t d i s t r i b u t i o n , r a t h e r t h a n t h e one term o f t h e c o n v e n t i o n a l t h e o r y .