The Frequency Modulation SOURCE set to External provides the modulating signal from an external source connected to the rear panel FM IN BNC connector.

This menu contains the external FM status window that shows the current menu selections and the measured FM Deviation (The FM deviation measurement function measures the voltage of the external modulation signal and calculates the peak frequency deviation).

The External FM menu is shown in Figure: External Frequency Modulation Menu.

Press: MODULATION | FREQUENCY | SOURCE | External

Press STATE to switch external FM on and off.

Sets the synthesis mode employed in generating the FM signal as Locked Low-Noise FM or Unlocked FM

If Locked low-noise is set, the YIG phase-locked loop is used in synthesizing the FM signal. If Unlocked is set, the YIG phase-lock loop is disabled and the FM signal is obtained by applying the modulating signal to the tuning coils of the YIG-tuned oscillator.

 

Press FILTER sets the high pass filter passband start frequency for the FM signal applied to the FM external input. Set DC for DC coupled, 63 Hz for a 63 Hz high pass filter, 1 kHz for a 1 kHz high pass filter as shown in Figure: FM Filter.

Press SENSITIVITY sets the FM sensitivity for the external FM function.
The FM Sensitivity range is –420000000 Hz/V to 420000000 Hz/V. (Range is model dependent)