Opereta S 572 A

The Opereta S 572 A is a mains-powered tube radio receiver made in Bucharest by Radio Popular, the factory that became Electronica in 1960 [1].

It is regarded as the first radio receiver of Romanian design and the head of the series of the Romanian radio industry, built partly with imported and partly with locally made components [1]. It was designed by engineer Eduard Evanovici. The book lists it among the four types assembled at Radio Popular in 1958, with the Victoria, Romanța and Balada, and elsewhere says it entered production in 1959 [1].

It was the first set built with the variable capacitors and dual potentiometers made for the first time in Romania, and it used a new piano-key waveband switch, designed by engineer Teodor Bădărău, instead of the rotary switch imported from the Soviet Union [1]. A production improvement by Gheorghe Terza, an experienced specialist from the old Philips team, simplified the input circuits: the medium-wave coil was eliminated and the long-wave coil was used, partly and with a suitable coupling, on medium waves as well [1].

It was made in two versions; the second added a magic-eye tuning indicator, tone control and front-mounted controls [1].

The memoirs of a Radio Popular engineer name the Opereta (1958) and the Concert (1959) as the factory’s first “hybrid” sets [2]. They were the first partly Romanian designs, adapted from imported standards, circuits and technology, and used Romanian loudspeakers, piano-key band switches and some other Romanian electrical parts [2].

In the source table, sensitivity is given for 50 mW output, selectivity at 1 MHz for ±10 kHz detuning, the audio frequency response at −6 dB relative to 400 Hz, and output power at 10% distortion [1].