For several years past, some of the progress made by Australian workers in the field of radio-frequency technique has been recorded in the A.W.A. Technical Review, published by Amalgamated Wireless (Australasia), Ltd., in Sydney. The first number of volume 7 (September 1946) of this publication contains several papers of interest, some of them describing measuring equipment developed by the above organisation. A resistance-capacitance beat-frequency oscillator covering the range 0–5,000 cycles per second is described by D. S. Robertson and L. C. Nye, certain features underlying the design having been developed theoretically in another paper by L. E. V. Lynch and D. S. Robertson. A description is also given by L. G. Alexander of an equal-ratio impedance bridge by means of which impedances can be measured to a precision of 1 per cent or better at frequencies up to 3 Mc./s.; while two special-purpose receivers covering the range of frequencies from 50 kc./s. to 50 Mc./s. are described by B. Sandel. In a paper entitled “Directional Patterns of Rhombic Antennæ”, W. N. Christiansen examines the spatial radiation patterns of typical rhombic antennæ in relation to that of a large tuned array, to which a single rhombic is inferior. After discussing various simple designs, the author shows that it is possible to arrange several rhombics in the form of an interlaced ‘end-on’ array so as to produce over the whole frequency range of the rhombic aerials a directional radiation characteristic which compares well with that of a tuned array at its single designed frequency. Other papers in this issue deal with such subjects as the application of a Geiger counter for determining the thorium content in wire used in valve manufacture, a radio-frequency form of high-tension supply for cathode-ray tubes, and a vacuum-sealed relay designed for operation with aircraft aerials transmitting at high voltages.