The paper describes the essential features of design and construction of field-strength measuring equipment for use at frequencies up to about 600 Mc/s, i.e. wavelengths down to about 50 cm. The equipment is of relatively narrow band-width (about 20 kc/s) and is primarily intended for the measurement of continuous-wave fields of the order of tens or hundreds of microvolts per metre. The paper is supplementary to a previous paper on the same subject and is intended to bring the information in the previous paper up to date in respect of recent practical and theoretical developments.An appendix to the paper briefly outlines the theory of the transference of received radio-frequency energy from an aerial to a diode detector or other load, by way of a closed tuned circuit.