Improvements in and relating to frequency changing arrangements for combined broadcast sound radio and television sets

摘要

770,218. Valve circuits for radio recepttion. SAUTIER & JAEGER. Oct. 13, 1954 [Oct. 16, 1953], No. 29473/54. Classes 40(5) and 40(6) In a combined receiver for television and sound broadcasting, a hexode mixer L1 and triode oscillator L2 are used for sound broadcasting frequencies the mixer L1 feeding into series-connected I.F. circuits T1, 2 tuned respectively to alternative high and low intermediate frequencies. For television, the oscillator L2 feeds a triode buffer frequency-doubler L4SP1/SP the anode of which is connected to the grid of a triode mixer L4SP11/SP. High-frequency television signals are supplied to the grid of the mixer L4SP11/SP by a tuned circuit av. The anode circuit comprises a video I.F. tuned circuit C from which sound I.F. is coupled into the sound I.F. channel via a link coupling Sp, Sr. In another embodiment, Fig. 3 (not shown) the buffer stage comprises a double triode with its grids fed in pushpull from the local oscillator, the anodes being connected to the mixer grid in parallel. The doubler is so biased that the fundamental frequency also appears in its anode circuit, so that this frequency also may be used for frequency-changing.