GB1226749A - - Google Patents

Abstract

1,226,749. Radio receiving apparatus; transistor amplifying, detecting and frequency changing circuits. TAPE SYSTEMS Ltd. 20 Jan., 1969 [19 Oct., 1967], No. 3168/69. Headings H3Q and H3T. A radio receiver module for use with a tape replay and/or recording machine designed for use with a cassette or cartridge is arranged to be fitted into the machine in place of the cassette or cartridge and comprises at least one amplifying stage, a demodulator and an output coil which is positioned so that it co-operates with the tape replay head. At its front end the module 1, Fig. 1, has an opening 2 which the capstan of the tape replay machine enters, though it does not engage any part of the module 1, and a further opening 3 entered by the tape replay head which couples to the output coil 4 but does not come into contact with it. Power is supplied to the module by means of a plug 5 which co-operates with a corresponding socket on the tape replay machine. Puch-button switches 6, for long waves, and 7, 8, 9 for medium waves are provided. The module includes a ferrite aerial having coupling windings 10, 11, Fig. 2, respectively for long and medium waves, coupled to switch contacts 12, 13 moving contact 14 connecting one or other coupling winding between the bases of transistors 19, 20 which comprise a long-tailed pair mixing circuit. Local oscillations are injected into the base of transistor 19 from oscillator transistor 21, the oscillator circuit comprising collector coupling coil 22 shunted by diode 26 and emitter coupling coil 23, both coupled to coupling coil 24. Moving contacts 43 of the push-button switches bring pretuned circuits 41, 45 in series with coupling coil 24, while moving contacts 42 bring pretuned circuits 40, 44 in series with one or other of the aerial windings 15, 16, respectively for long and medium waves. Mixer transistor 19 feeds via I.F. filter 27 into cascaded emitter followers 28, 29 which are coupled to a commonemitter amplifier stage 30. Amplifier 30 feeds into a detector 31 the output of which is fed via resistor 30 and capacitor 30A to the coupling coil 4. The D.C. output of detector 31 is applied via resistors 34, 35 to the mixer as a.g.c.