A modulator employs a pair of variable RF attenuators to produce a double sideband, suppressed carrier output. The attenuator devices are PIN diodes which are rendered alternately conductive in synchronism with the recurring half cycles of the audio frequency input signal which is to be impressed upon the radio frequency signal as modulation. As each diode conducts the RF signal, its attenuation is varied by a control signal in a manner to provide the conducted RF signal with a modulation envelope that follows the amplitude of the audio input. The modulated signals from both diodes are combined at the modulator output, after a phase reversal of the modulated signal from one of the diodes, in order to thereby provide a double sideband, suppressed carrier output signal. The control signal for each conducting diode is produced by a function generator operating within a closed loop feedback system. The generator receives the audio input and a recreated modulating signal derived without carrier insertion from an envelope detector on the modulator output, and compares the recreated modulation with the original audio input to provide the control signal with the proper wave shape. An electronic goniometer for a VOR navigation system employs two of the double sideband modulators responsive to 30 Hz input signals that are 90.degree. out of phase; thus a 90.degree. modulation envelope phase difference exists at the goniometer outputs as required for the variable phase antenna feeds of a VOR transmitting system.