The 11715A AM/FM test source delivers very flat, low-distortion amplitude, and wide-bandwidth – or frequency-modulated RF signals. Primarily made for testing of performance as well as adjustments of the 8902A measuring receiver and 8901A/B modulation analyzer, it has the function of a high-quality modulated test oscillator where the frequency range is applicable. The major components of the 11715A are a low-noise voltage-controlled oscillator (VCO), a double-balanced mixer and 2 digital dividers. The main signal source is the VCO, with a typical frequency range of 330 to 470 MHz at the FM output. FM’s produced by linking the external modulation source to the tune input of the VCO directly, giving extremely wide bandwidth modulation with a phase shift that’s low. Also, this design ensures very little incidental AM. The 11715A can also be used in conjunction with an 8902A and an 8901A/B as a calibrated signal source for special applications. In particular, the U.S. commercial FM broadcast band of 88 to 108 MHz is covered by the FM divide-by-4 output of the 11715A.