Given the following: (1) audio power for 100% modulation equals 50% of DC input power to RF modulated amplifier, (2) load presented to the modulated tube consists of the DC plate impedance of the modulated amplifier, (3) constant grid excitation voltage, very lot distortion, what type of modulation?
• AM (Amplitude Modulation) power relationships between RF carrier and audio power at 100% modulation • How the modulating audio is applied in different modulation types (grid, plate, cathode, anode) • Effect of where the modulation is applied on linearity/distortion and on DC input power
• Think about which modulation method uses the DC plate (anode) supply as the place where the audio is applied to vary the RF output • Ask yourself: when the load is described as the DC plate impedance and the grid excitation is constant, which element in the tube circuit is actually being modulated? • Consider which method is known for relatively low distortion and efficient use of DC input power at 100% modulation.
• Identify which option(s) correspond to modulating the plate/anode circuit versus the grid or cathode • Confirm which modulation method results in audio power being about 50% of the DC input power to the RF stage at 100% modulation • Verify which method keeps the RF drive (grid excitation) constant while the supply to another electrode is varied by the audio signal
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