GB613152A - Improvements in or relating to bandspread tuning devices for radio apparatus - Google Patents

Abstract

613,152. Radio receiving circuits. PHILIPS LAMPS, Ltd. April 17, 1946, No. 11782. Convention date, July 1, 1941. [Class 40 (v)] In a band-spread tuning arrangement in which the wave-band is determined by connecting one of a number of inductors to a circuit comprising a variable condenser and one or more fixed condensers, further inductance is added in series with the variable condenser or with each of the condensers in order that the absolute value of the frequency range in two or more bands may be equalized. In Fig. 1, switch 5 selects the inductor 2, 3 and 4 required for the wave-band. A further inductor 7 is connected in series with the band-spread tuning condenser 6 and this reduces the effective variation in capacitance of the condenser, the reduction being greater at higher frequencies. By this means the absolute value of the frequency range is equalized in two bands, the deviation in the third being small. Equalization in the third band also may be obtained by the addition of further condensers and inductors 8 to 11 as shown in Fig. 2. In an alternative arrangement, Fig. 3 (not shown), for higher frequencies, the inductors are formed by the connecting leads between the components.