VHF Television tuner with easy/flexible access

摘要

A VHF television tuner for selection of a broadcasting television signal through mechanical switching selection of inductance coils, comprising; a tuner casing; a mechanical channel selection switch arrangement provided in said casing and including a rotatably mounted channel selection shaft for selection of inductance coils by rotation of said shaft; a radio frequency amplifier operatively coupled to the selected inductance coils for selectively amplifying a desired radio frequency signal; a local oscillator operatively coupled to said selected inductance coils for providing a local oscillation frequency signal, the frequency of which is different by a given frequency difference from said selectively amplified radio frequency signal; a mixer responsive to the radio frequency signal from said radio frequency amplifier and the local oscillation frequency signal from said local oscillator for providing an intermediate frequency signal; and an intermediate frequency tuned circuit for selectively withdrawing said intermediate frequency signal, said intermediate frequency tuned circuit comprising an intermediate frequency transformer, said intermediate frequency transformer comprising an intermediate frequency coil wound around a bobbin having a given axis and a magnetic core threadably inserted in said bobbin for adjustment of the inductance value of said intermediate frequency coil by rotation of said magnetic core about said axis of said bobbin, said intermediate frequency transformer being provided in said casing such that the axis of said bobbin is oriented in the direction substantially parallel to the axial direction of said channel selection shaft, said casing being formed of an aperture at the position in alignment with the axis of said bobbin, whereby access to said intermediate frequency transformer is allowed from the outside of said casing for adjustment of the inductance value of said intermediate frequency transformer.