Radio receiver for equi-spaced channels - has comb filter and heterodyne oscillator functioning at certain frequencies only switched between two groups of channels

摘要

The multichannel, suppressed carrier receives includes a bandpass filter which covers an entire frequency band. By means of a switchable comb filter the receiver responds to a first series of transmissions or to a second series having frequencies interposed between those of the first. The comb filter includes a delay line (8) coupled to an adder stage (9) and a sub-tractor stage (14) which can be selected by a switch (17). The heterodyne oscillator includes a comparator oscillator (18) which has an ultrasonic delay line (19) as its frequency standard. The comparison voltage is fed by way of a switch (22) to a phase discriminator (23) which controls heterodyne oscillator (24). This control determines that in the first switch position the oscillator generates the first series of frequencies and that in the second position, the frequencies are shifted by a predetermined amount.