Grid-Bias Modulation

Author: J.B. Hoag

Figure 28 D shows a Class C amplifier modulated by the grid-bias method.

Fig. 28 D. Grid-bias modulation of a r.f. Class C amplifier. The by-pass condenser C should not be greater than approximately 0.002 μfd.

In this circuit it is necessary that the plate supply of the modulator should have good voltage regulation, and that the grid-bias source for the amplifier should have low resistance. A battery might well be used, or a rectifier with regulated output. A grid-leak bias should not be used. The C-bias should be two or three times the cutoff value.