A frequency changer arrangement is provided for a radio frequency tuner.
The arrangement comprises a first quadrature frequency changer for
converting a desired input channel to zero or near-zero intermediate
frequency in-phase and quadrature signals. These signals are filtered by
low pass filters, whose turnover frequencies may be varied so as to vary
the intermediate frequency bandwidth. A second quadrature frequency
changer upconverts the filtered signals and supplies these to a summer.
The resulting output intermediate frequency is determined by the
frequency of commutation signals in the second frequency changer so that
the output intermediate frequency may be continuously varied to allow any
desired frequency to be selected.