Draw the circuit diagram of practical diode detector and explain its working. 

1 Answer

Answer :

Circuit diagram of practical diode detector: 

image

Explanation- The circuit operates in the following manner- The diode has been reversed so that now the negative envelope is demodulated. Due to this negative AGC voltage will be developed.R1 and R2 ensures that there is a series DC path to ground for diode. R1 and C1 is the low pass used to remove RF ripple that is present in the detector o/p. C2 is coupling capacitor that prevents the diode DC o/p from reaching the volume control R4. Hence across R4 demodulated output is with zero dc shift which is applied to the AF amplifier. R3 and C3 is a low pass filter which removes AF components and helps to produce AGC voltage. The DC AGC voltage is proportional to the amplitude of AM signal. 

Related questions

Description : Draw the circuit diagram of varactor diode FM modulator and explain its working.

Last Answer : Varactor diode modulator is the direct method of FM generation wherein the carrier frequency is directly varied by the modulating signal. A varactor diode is a semiconductor diode whose ... the magnitude of frequency change is proportional to the amplitude of the modulating signal voltage.

Description : Draw and label the circuit diagram of ratio detector 

Last Answer : Draw and label the circuit diagram of ratio detector  

Description : Draw circuit diagram of transistor reactance modulator. Explain its working.

Last Answer : Explanation- A reactance modulator is illustrated in figure. It is basically a standard commonemitter class A amplifier. Resistors R1 and R2 from a voltage divider to bias ... frequency, whereas a lower capacitance increases the frequency. The circuit produces direct frequency modulations.

Description : Draw the circuit diagram of limiter and explain its working.

Last Answer : Circuit diagram of amplitude limiter:- Explanation:- 1. In frequency modulation, the signal amplitude is held constant while the carrier frequency is varied. 2. Any noise that contaminates ... V p-p instead of the alternately driven into saturation and cutoff, it limits the signal amplitude

Description : Explain working of envelope detector with suitable diagram and waveform.

Last Answer : Envelope Detector: An Envelope Detector is an electronic circuit that takes a high frequency signal as input and provides an output which is as envelopes of the original signal. The capacitor ... decreases the responsiveness thus, real-world designs must be optimized for the application.

Description : Explain the demodulation of AM signal using diode detector.

Last Answer : Simple diode detector:- Explanation:- This is essentially just a half wave rectifier which charges a capacitor to a voltage nearly to the peak voltage of the incoming AM waveform s(t). ... detector output is proportional to the signal strength. Stronger Am signal higher is the dc AGC voltage.

Description : Draw the TRF receiver block diagram and explain its working. 

Last Answer : Explanation:- 1. TRF receivers are simple and having high sensitivity. The AM transmission takes place in MW band and SW band. MW frequency range is 540KHz to 1640KHz. 2. ... power level to drive the loudspeaker. 7. The loudspeaker converts electrical signal into original sound information.

Description : Draw the diagram for PAM generation using transistors. Explain its working.

Last Answer : Explanation:-1. Transistor Q1 is used in the active region so it has been provided with DC biasing to its base. 2. Modulating signal is applied to the base of transistor Q1 3. In the emitter of ... . 7. In the time interval between sampling pulses output is zero. Thus we get the output as PAM.

Description : Explain with a neat diagram of ratio detector. Why limiter stage is not used before ratio detector.

Last Answer : With diode D2 reversed , O is positive with respect to b, so that Vab is a sum voltage rather than the difference it was in the discriminator it is now possible to connect a large capacitor ... of limiter stage due to large capacitor C5 .Hence, limiter stage is not used in ratio detector.  

Description : Draw block diagram of FM receiver and explain the use of limiter circuit.

Last Answer : Diagram Explanation Amplitude limiter: The function of amplitude limiter is to remove all amplitude variation of FM carrier voltage that may occur due to atmospheric disturbances. Use of amplitude limiter makes the system less noisy.

Description : Draw practical set-up and explain the procedure to measure selectivity of radio receiver.

Last Answer : Procedure to measure selectivity of radio receiver: Throughout the measurement the receiver is kept tuned to desired frequency 950 Khz. Now the generator output frequency is deviated below ... the generator output voltage is adjusted to get a standard 50 miliwatt receiver output power.

Description : Draw the practical AM diode detector circuit. Sketch its input and output waveforms. 

Last Answer : Practical AM diode detector 1. Skip distance:-Skip distance is defined as the shortest distance from a transmitter, measured along the surface of earth at which a sky wave of fixed frequency ... had taken place from a surface located at a greater height, called Virtual height of this layer.

Description : Draw the circuit diagram of PWM using IC555. State its operation.

Last Answer : Operation: i. The timer IC555 is operated in monostable mode. ii. The negative going carrier pulses are to the differentiator formed by R1 & C1. The differentiator produces sharp negative ... . Thus PWM signal is generated at the output pin (3) of IC555 as monostablemultivibrator. 

Description : Explain the working of amplitude limiter in FM receiver with circuit diagram.

Last Answer : Amplitude limiter: The function of amplitude limiter is to remove all amplitude variation of FM carrier voltage that may occur due to atmospheric disturbances. Use of amplitude limiter makes the system less noisy  Circuit Diagram:

Description : Draw the block diagram of AM transmitter, explain its operation.

Last Answer : AM transmitter is of two types i)High Level AM Transmitter ii)Low Level AM Transmitter i) RF crystal oscillator: It is a source of carrier signal of desired frequency. The circuit is ... AM signal is then applied to the transmitting antenna which radiates this AM signal into air or space. 

Description : Draw and explain block diagram of electronic communication system.

Last Answer : Block diagram of electronic communication system. Explanation Transducer: A transducer is usually required to convert the output of a source into an electrical signal that is suitable for ... etc. Output Transducer: The output transducer converts electrical signal in to sound signal.  

Description : Draw the block diagram of PWM. List its advantages 

Last Answer : Block diagram of PWM:- Advantages of PWM:- 1. More immune to noise. 2. Synchronization between transmitter and receiver is not required. 3. Possible to separate out signal from noise.

Description : Draw block diagram of basic electronic communication system and state the function of each block.

Last Answer : i) Input signal: - The information can be in the form of sound, picture or data coming from computer. ii) Input transducer: - it converts original information into equivalent electrical ... back to suitable form. vii) Output transducer: - It converts electrical signal into original form. 

Description : Draw the block diagram of FM super heterodyne radio receiver with waveforms.

Last Answer : block diagram of FM super heterodyne radio receiver

Description : Explain operation of balanced slope detector with „s‟ curve.

Last Answer : Diagram: Explanation:   Curve:  

Description : List the types of FM detector. Explain any one of them.

Last Answer : Types of FM detector:- 1. Simple slope detector 2. Balanced slope detector 3. Phase discriminator(Foster seely discriminator) 4. Ratio detector 5. PLL detector Simple ... . If the IF amplitude is sufficiently limited prior to reaching the PLL and the loop is properly compensated 

Description : With the help of neat diagram, explain the working of phase discriminator.

Last Answer : Explanation:- This discriminator is also known as the center tuned discriminator or the Foster Seeley discriminator after its inventors. It is possible to obtain the same S- Shape response curve from a circuit in ... fin = fc, fin > fc + Δf and fin<fc- Δf should be given marks

Description : Define pre-emphasis. State its need. Draw the circuit of pre-emphasis.

Last Answer : Definition- The artificial boosting of higher modulating frequencies to reduce the effect of noise is called as pre-emphasis. Need:- The artificial boosting of higher audio modulating ... by increasing the amplitude of modulating signal at higher frequencies. Circuit diagram 

Description : What are the different types of FM detector?

Last Answer : The different types of FM Detectors are: 1. Simple Slope Detector 2. Balanced Slope Detector 3. Ratio Detector 4. Phase Discriminator 5. FM Detector using Phase Locked Loop (PLL) 

Description : Define the transmission line? Draw it‟s general equivalent circuit.

Last Answer : Transmission line: A conductor or conductors designed to carry electricity or an electrical signal over large distances with minimum losses and distortion.  Equivalent circuit:

Description : Draw general equivalent circuit of transmission line.

Last Answer : Fig. General Equivalent circuit of transmission line 

Description : Explain loop antenna with neat sketch. Draw radiation pattern. State its advantages and applications.

Last Answer : Loop antenna:-The single turn coil carrying RF current through it having length less than the wavelength.   Advantages:- 1. highly directive 2. Small size Applications:- 1. For direction finding 2. In portable receivers 3. In navigation 

Description : Draw construction of Yagi-Uda antenna and explain.

Last Answer : Explanation A Yagi-Uda antenna, commonly known as a Yagi antenna, is a directional antenna consisting of multiple parallel elements in a line, usually half-wave dipoles made of ... receiver with a transmission line and additional parasitic elements called reflector and one or more directors.

Description : Draw and explain PLL as an FM demodulator.

Last Answer : Explanation:- FM signal which is to be demodulated is applied to input of PLL.VCO output must be identical to input signal if PLL is to remain locked. As PLL is locked, VCO ... error voltage represents the modulating signal. Thus at the error amplifier output we get demodulated FM output.

Description : Explain with block diagram of Armstrong method of FM generation.

Last Answer : Explanation:- The crystal oscillator generates the carrier at low frequency typically at 1 MHz this is applied to the combining network and a 90o phase shifter. The modulating signal is passed through an ... power amplifier to raise the power level of the FM signal.  Phasor Diagram:-   

Description : Explain skip zone and skip distance with neat diagram.

Last Answer : Skip distance:-Skip distance is defined as the shortest distance from a transmitter, measured along the surface of earth at which a sky wav of fixed frequency returns back to the earth. Skip zone: skip zone where signal is not detectable

Description : Draw Yagiuda antenna with its radiation pattern.

Last Answer : Construction of Yagi-Uda Antenna Radiation Pattern of Yagi-Uda Antenna

Description : Draw the structure of horn antenna and its radiation pattern. List its any two applications.

Last Answer : The structure of horn antenna Radiation pattern of Horn Antenna Application:- i) Used at microwave frequency. ii) Used in satellite tracking 

Description : Draw the diagram of zero crossing detector using op-amp and explain its working.

Last Answer : The zero crossing detector circuit is an important application of the op-amp comparator circuit. It can also be called as the sine to square wave converter. Anyone of the inverting or non-inverting ... the possibility of any false zero crossing due to noise voltages at the op-amp input.

Description : Draw the structure and state applications of: i) Ferrite loop (rod) antenna ii) Horn antenna

Last Answer : Horn antenna: Application:- i) Used at microwave frequency. ii) Used in satellite tracking.  Ferrite loop antenna: Application:- In Am radio receiver to receive MW and SW band signals. In FM radio receiver

Description : Draw waveform for standing waves on an open and shorted line. Prove that impedance is inverted at every quarter wavelength interval.

Last Answer : Waveform- Explanation When the transmission line is short circuited voltage is zero and current is maximum.The variation is according to the wavelength. When the ... The pattern repeats for every half wavelength. Thus impedance is inverted at every quarter wavelength interval.

Description : In a FM system, the maximum deviation is 75KHz. Find bandwidth for modulating frequency i. fm=500Hz ii. fm=5KHz iii. fm=10KHz Draw conclusion for bandwidth of FM from answer.

Last Answer : Given deviation∆=75kHz i) fm=500Hz bandwidth B.W=2(∆+fm)  =2(75k+500)=151kHz  ii). fm=5KHz bandwidth B.W=2(∆+fm)  =2(75k+5k)=160KHz iii) fm=10KHz bandwidth B.W=2(∆+fm)  =2(75k+10k)=170KHz As the modulating frequency increases bandwidth also increases.

Description : Define PAM, PWM, and PPM. Draw waveforms.

Last Answer : Pulse amplitude modulation is defined as a process of varying the amplitude of the carrier pulse in accordance to the modulating signal variations. Pulse width modulation is defined as a ... of varying the position of the carrier pulse, in accordance to the modulating signal variations.

Description : Draw radiation pattern for following antenna i) Yagi-Uda antenna ii) Loop antenna iii) Dish antenna iv) Horn antenna

Last Answer : Type of antenna Radiation Patteren  Yagi-Uda antenna Loop antenna Dish antenna Horn antenna 

Description : Draw the radiation pattern for Dipole antenna: (i) Half wave dipole (ii) Folded dipole.

Last Answer : The radiation pattern for Half wave dipole antenna The radiation pattern for Folded dipole antenna.

Description : Draw amplitude modulated waveform in time domain and frequency domain with proper labeling.

Last Answer : AM in Time domain  AM in frequency domain

Description : Describe the block diagram of FM superhetrodyne receiver

Last Answer : RF amplifier:- There are two important functions of RF amplifier: 1) To increase the strength of weak RF signal. 2) To reject image frequency signal. In FM broadcast the ... FM broadcast, the maximum modulating frequency is 15 kHz. Hence the audio amplifier must have large bandwidth.

Description : Describe the block diagram of basic communication system.

Last Answer : Describe the block diagram of basic communication system.

Description : Describe the term virtual height with the help of diagram showing ionized layer and the path of wave.

Last Answer : Virtual height: -The incident wave returns back to the earth due to refraction. In this process it bends down gradually and not sharply, but the incident and reflected rays follow exactly ... . It is also defined as the maximum height that the hypothetical reflected wave would have reached. 

Description : Sketch circuit diagram of positive biased clipper using diode and explain its working.

Last Answer : Positive Series Clipper with positive Vr. The following figure represents the circuit diagram for positive series clipper when the reference voltage applied is positive. During the positive cycle ... Hence the input signal that is greater than the reference voltage, appears at the output.

Description : Explain half dipole antenna ( Resonant antenna ) with its radiation patteren. 

Last Answer : Half wave dipole antenna Explanation:  1. It is a resonant antenna 2. It is exact half wavelength (λ /2) long & open circuited at one end. 3. The dipole antennas have ... pattern is bidirectional.  The radiation pattern of half wave dipole antenna is - The radiation pattern

Description : State the need of stub. Explain single stub and double stub matching.

Last Answer : Stub:- Stub is the piece of short circuited transmission line which is used to tune out the reactance of the load when connected across the transmission line as close as possible. ... but lengths are independently adjustable. The double stub matching provides wide range of impedance matching.  

Description : Explain duct propagation with neat sketch.

Last Answer : Duct propagation is a special type and used for very high microwave frequencies. New phenomenon which occurs in super-refraction, also known as ducting. As the height above earth increases, ... in the standard atmosphere. The Duct propagation is used for very high frequencies in GHz range.

Description : Define and explain the term beam width related to antenna with a sketch.

Last Answer : Definition: The beam width of an antenna is described as the angles created by comparing the half power point (3dB) on the main radiation lobe to its maximum power point. As an example the beam width ... max voltage at center of lobe (these point are known as half power points.) Sketch-  

Description : State and explain the concept of transmission bandwidth.

Last Answer : Bandwidth is defined as the portion of the electromagnetic spectrum occupied by a signal We may also define the bandwidth as the frequency range over which as information signal is transmitted. Bandwidth is the ... to 15 KHZ. Therefore the bandwidth is(f2-f1) BW= f2 - f1= 15000-20=14980Hz