A sweep output generator in which an a-c voltage of small amplitude is superimposed upon a sweep voltage applied to a variable reactance element of a local sweep voltage controlled oscillator for sweeping the local oscillator frequency and also for frequency modulation. The frequency modulated local sweep oscillator output and the output of a second voltage controlled oscillator are coupled to a mixer to obtain an intermediate frequency signal. The intermediate frequency signal is frequency demodulated through a frequency discriminator, whose output is in turn integrated to obtain a sweep output voltage of a characteristic similar to the normalized oscillation frequency versus impressed voltage characteristic of the local oscillator.