GB541867A - All-wave loop receiver - Google Patents

Abstract

541,867. Wireless receiving apparatus. PHILCO RADIO & TELEVISION CORPORATION. May 2, 1940, No. 7920. Convention date, June 3, 1939. [Class 40 (v)] A multi-band receiver has a loop aerial 2 for medium and long wave reception arranged in a vertical plane for directional use and a short wave loop 3 arranged in a horizontal plane. The loop 2 is preferably arranged near the back of the set and the loop 3 is arranged inside the top of the set so that the plane of one loop bisects the other loop and reduces undesired coupling. The short wave loop consists of a single turn of enamelled copper wire wound on a notched sheet of insulating material carrying terminals (Fig. 2, not shown). The aerials may be connected to the set by ganged switches S1, S2, S3. In position A, loop 3 is open circuited, while loop 2 is connected across tuning condenser 14 by switches S1, S3. In position B, loop 3 is open circuited, part of loop 2 between leads 15, 16 is grounded by switches S2, S3, and part of loop 2 between leads 15, 17 is connected across condenser 14 by S1, S2. In position C loop 2 is open circuited, and loop 3 is connected across 14 by switches S1, S3. An external aerial may be connected to terminal ANT. The receiving circuit comprises an R.F. valve V1, resistance capacity coupled to a frequency changer V2, the subsequent stages being transformer coupled. A resistance damped peaking coil 24 in the plate lead of V1 is adjusted to resonate with the input capacity of V2 at some frequency in the short wave band. A full A.V.C. voltage is fed from the anode of the second detector V4 to the I.F. amplifier V3 while a fraction of the A.V.C. voltage is fed to the R.F. valve V1 from a voltage divider 27 connected across the detector load resistance 28, with suitable delay if required. The coupling transformers may be screened from the aerial loops by the provision of spaced screens of low permeability tinned steel or of non- magnetic metals.