The 8640B is a cavity tuned oscillator with the base model able to generate a AM/FM modulated signal between 500 KHz - 512 MHz (450 KHz - 550 MHz with overrange).

Options:

Option 001: Internal Variable Audio Oscillator (20 Hz - 600 KHz)

Option 002: Internal Doubler (increases range to include 512 MHz - 1024 MHz

Option 003: 50 W Reverse Power Protection

Option 004: Avionics Testing Option

Option 005: Improved level accuracy, lower SSB Phase Noise, and 1dB step attenuator

Option 323: Militarized version, also known as 8640M