Radio Receivers

Automatic Frequency Control Block Diagram: Automatic frequency control: As previously we see, the heart of an AFC circuit is a frequency-sensitive device, such as the phase discriminator, which produces a dc voltage whose amplitude and polarity are proportional to the amount and direction of the local oscillator frequency error. This dc control voltage is then […]

Squelch Circuit: Squelch (muting): When no carrier is present at the input, i.e., in the absence of transmissions on a given channel or between stations, a sensitive receiver will produce a disagreeable amount of loud noise. This is because AGC disappears in the absence of any carrier. The receiver acquires its maximum sensitivity and amplifies the

Delayed Automatic Gain Control: Delayed Automatic Gain Control: Simple AGC is clearly an improvement on no AGC at all, in that the gain of the receiver is reduced for strong signals. Unfortunately, as Figures 6-14 and 6-19 both show, even weak signals do not escape this reduction. Figure 6-19 also shows two other AGC curves.

Communication Receiver Block Diagram: A Communication Receiver Block Diagram is one whose main function is the reception of signals used for communications rather than for entertainment. It is a radio receiver designed to perform the tasks of low- and high-frequency reception much better than the type of set found in the average household. In turn,

Working Principle of Automatic Gain Control: Working Principle of Automatic Gain Control is a system by means of which the overall gain of a radio receiver is varied automatically with the changing strength of the received signal, to keep the output substantially constant. A de bias voltage, derived from the detector as shown and explained

Simple Diode Detector: Operation of diode detector: The Simple Diode Detector is by far the most common device used for AM demodulation (or detection), and its operation will now be considered in detail. On the circuit of Figure 6-12a, C is a small capacitance and R is a large resistance. The parallel combination of R

Intermediate Frequency Amplifier: Choice of frequency: The Intermediate Frequency Amplifier (IF) of a receiving system is usually a compromise, since there are reasons why it should be neither low nor high, nor in a certain range between the two. The following are the major factors influencing the choice of the Intermediate Frequency Amplifier in any

Frequency Changing and Tracking in Receivers: The mixer is a nonlinear device having two sets of input terminals and one set of output terminals. The signal from the antenna or from the preceding RF amplifier is fed to one set of input terminals, and the output of the local oscillator is fed to the other

Transistor RF Amplifier Circuit: A radio receiver always has an RF section, which is a tunable circuit connected to the antenna terminals. It is there to select the wanted frequency and reject some of the unwanted frequencies. However, such a receiver need not have an Transistor RF Amplifier Circuit following this tuned circuit. If there

Superheterodyne Principle: The block diagram of Figure 6-2 shows a basic superheterodyne receiver. In the Superheterodyne Principle, the incoming signal voltage is combined with a signal generated in the receiver. This local oscillator voltage is normally converted into a signal of a lower fixed frequency. The signal at this intermediate frequency contains the same modulation