GB254327A - Receiving apparatus for electric oscillatory signals - Google Patents

Abstract

254,327. Aigner, F. June 24, 1925, [Convention date]. Thermionic heterodyne receivers. - Multiple reflex amplification is rendered practicable by changing the frequency after each amplification, the series of frequencies employed for this purpose being derived by heterodyning with successive harmonics of the local generator. By choosing the frequencies in this manner, howling due to undesired heterodyne action can be avoided. The switch P enables a loosely coupled valve H2 to be inserted in series with the valves H for the purpose of eliminating atmospherics. Superheterodyne multiple amplification. Incoming signals are heterodyned to produce an oscillation of constant high frequency N1 which is applied through the transformer T1 to the high frequency amplifier H. The local oscillator G generates a fundamental frequency N with harmonics, the fundamental and the first three harmonics being respectively selected by the tuned coupling circuits K1, K2, K3, K4, and combined with the incoming frequency N1 to produce a series of beat oscillations of frequencies N2. N3, N4, N5, which are successively amplified by the valve H. The generator frequency N is made equal to four times the lowest difference frequency, so that in this case N = 4 N5 : then the remaining differences N4, N3, N2, N1 are odd harmonics of N5, which forms the fundamental of the series of difference frequencies. Thus the frequency N1, derived through the transformers T6, combines with the harmonic 4 N, derived through the circuit K4, to produce a frequency N2, which appears in the output of the modulator M1, is selected by the doubly-resonant transformer T2, and amplified by the main amplifier H. The amplified oscillations of frequency N2 are then selected by the doubly resonant transformer T7, combined with the harmonic 3 N from the circuit K3, and applied to the modulator M2, the resulting beat oscillations of frequency N3 being selected by the doubly resonant transformer T3, and amplified by the main valve H. The amplified oscillations of frequency N3 are in a similar manner combined with the harmonic 2N to produce a frequency N4, which after amplification by the main valve H, combines with the fundamental N to produce a beat frequency N5 which is amplified by the valve H and passed through the transformer T5 to the wireless receiver J. Thus the modulators M1, M2 extract the beat frequencies arising from the harmonics of odd and even number respectively, and the valve H serves to amplify each beat frequency in succession. Reaction coupling. Reaction may be effected bv introducing the coupling coils S1, S2, shown in dotted lines, between the circuits of the modulators M1, M2.