GB890900A - Television receivers - Google Patents

Abstract

890,900. Radio receiver apparatus. MURPHY RADIO Ltd. Sept. 16, 1960 [Aug. 27, 1959], No. 29360/59. Class 40(5). In a television receiver for 405 line and 625 line or similar systems, the I.F. vision amplifier has high attenuation at the sound I.F. of the 405 line transmission and substantially uniform amplification over the range of four or more m/cs., the receiver having coils selected by a channel and line standard selector which places the vision I.F. of the 405 line transmission approximately 3.5 mc/s. below the upper region of high attenuation and the vision I.F. of the 625 line on or near the upper edge of the passband. The I.F. response curves shown in Figs. 3 and 4 have a 4 mc/s. passband and high attenuation points at 38.15 and 33.15 mc/s. corresponding to the sound and adjacent-channel sound carriers of the 405 line system, the vision carrier of the 405 line system being located at 34.65 mc/s. as shown in Fig. 3. The absence of the usual sloping response associated with the vestigal sideband transmission is compensated elsewhere in the receiver. For 625 line transmissions the I.F. vision carrier of 37.65 mc/s. is located as shown in Fig. 4. The I.F. sound carrier is located at 31.65 mc/s. where there is sufficient response to permit the osc. of the "inter carrier" sound system, Fig. 5 (not shown). Alternatively the sound signals for both 405 and 625 systems may be extracted immediately after the frequency changer (Fig. 6, not shown).