A field-strength measuring set, capable of operation over the frequency range 400 to 4 000 Mc/s, has been designed and constructed. The mixing unit employs a local oscillator of range 400 to 800 Mc/s, and is used with a wide-band i.f. amplifier, 0.5 to 3.5 Mc/s. Harmonic frequencies of the local oscillator are used to receive signals on frequencies higher than 800 Mc/s. It is possible to use the receiver with several types of antenna, and the equipment is normally supplied by batteries.