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8-18 Balanced Ratio Detecto:

The above detector is unbalanced because D and D2 are unbalanced against ground. This circuit can be converted to balance and become a balanced ratio detector, by moving the ground connection point as in the figure

(18-20) Instead of resistance R, we now have two resistors, and their work remains the same. The resistance: has been introduced to secure the best balance between both halves of the circuit - and R2 determines the withdrawal of the elevator current from each binary - and the capacitor C keeps the medium frequency voltage IF away from the audio output. As for C - R3, they are a Deemphasis filtering circuit, as this circuit returns the amplitude to the signal to prevent the loss or distortion of the amplitude of the audio signal, as well as reducing the level of higher frequencies that have distortion on the sound. The automatic gain adjusting AGC voltage can be obtained from the negative terminal of the capacitor and the regulatory capacitor C of capacitance (4uF).

note :

Some valves have been used as FM detectors and they are designed to have the characteristics of the discriminator and determinant, and there is no need to explain them because they are not used at the present time, including valve 6BN6, valve 6DT6, and valve 3DT6, which are similar to the five-valve.

9-18 T.Quadrature Detector: Detector)

It consists of three transistors identical to each other, and they are integrated into one integrated circuit IC as in Figure (18-21) and may be part of an integrated circuit that contains other circuits such as the IF amplifier and the audio frequency amplifier.

circuit work:

The IF signal is of sufficient gain before it enters this circuit, so that it occupies Q1 and Q2 with appropriate power and the output signal of the radiators resembles a rectangular wave.

. In Figure (A-22-18), the transistor works like network 1 and network 3 in the valve (6BN6), and the phase shift is (290) in transistor Q2 by directing it through a small capacitor (4PF). at the resonance frequency. It has (55) MHz, which is the central frequency, but it shifts the phase of the signal linearly at small changes in frequency from the resonant frequency, as in Figure (18-22), and the net result of (and 02) in the perpendicular detector is as in Figure A. They are wider pulses above resonance and narrower pulses below resonance. The transistor Q3 only amplifies the pulses before they go out to the audio output - and the transistor Q3 has a grounded base circuit - and the output capacitor (0.01 microfarad) removes the IF component from the audio signal.