GB642344A - Improvements in or relating to radio receiving apparatus - Google Patents

Abstract

642,344. Frequency measuring. DEPARTMENT OF COMMERCE, DIRECTOR OF THE OFFICE OF TECHNICAL SERVICES OF. Feb. 27, 1948, No. 5971. Convention date, Nov. 27, 1945. [Class 37] [Also in Group XL (c)] A radio receiver comprises a plurality of oscillator and amplifier sections so connected that one part of the output of each amplifier is directly amplified, and the remainder of the output is amplified after frequency conversion, by the next amplifier, each amplifier having a band width one half the width of its predecessor. The arrangement enables a narrow band amplifier to be used in a receiver which is responsive, without variation of tuning, to all signals in a wide frequency band. Fig. 1 shows part of a radio receiver in which all incoming signals in the frequency band of, for example, 100 mc/s. to 120 mc/s are mixed in frequency converter 11, with signals at 110 mc/s. from oscillator 12. The first amplifier 13 passes frequencies 'between 1 mc. and 10 mc/s. and therefor amplifies all beat frequencies corresponding to signals between 100 and 120 mc/s. except for a null between 109 and 111 mc/s. The output from the first amplifier is applied to a second amplifier 16 which passes frequencies between 6 mc/s. and 10 mc/s. The portion of the output from amplifier 13 between 6 and 10 mc/s, is amplified directly by amplifier 16, while that between 1 and 5 mc/s. is first converted by mixing with oscillations at 11 mc/s. from oscillator 15. The frequency of an incoming signal may be determined by varying the frequency of oscillator 12 until the signal disappears due to the presence of the null which exists around the particular frequency of the oscillator.