Simple field strength indicator circuit enables us to check whether an RF based transmitter is transmitting the signal or not. If any fault is present, that is quickly checked.
Basically it detect all forms of Rf frequencies and let's the user know through meter deflection. Higher deflection reveal stronger RF from the transmitter and vice versa.
How it Works
In this field strength meter circuit a BJT transistor is the only active element in the circuit. The transistor here is utilized as a control resistance in one of the arms of a metering bridge. The transistor’s base is connected to the wire or the rod aerial.
The transistor is driven by the increasing HF voltage at the base of the aerial drives. This enables the bridge to bring to equilibrium.
After that, current flows through R2, the mA meter, as well as the collector-emitter junction of the transistor. Before switching on the transmitter, the meter must be brought down to zero with P1.