Define: (i) Image frequency and (ii) Double spotting

Define: (i) Image frequency and (ii) Double spotting
by

1 Answer

Answer :

i)Image frequency:- Image Frequency is defined as the signal frequency plus twice the intermediate frequency. It is denoted as fsi = fs+2fi

Where,

fs = Signal Frequency

fi =intermediate frequency.

ii)Double spotting:-

Double spotting means the same stations get picked up at two different nearby points,on the receiver dial.

It is due to the poor front end selectivity i.e., inadequate image frequency rejection.


by

Related questions

A superheterodyne radio receiver with an IF of 455KHZ is turned to 1000KHZ. Find: (i) Image frequency (ii) Local oscillator frequency

Description : A superheterodyne radio receiver with an IF of 455KHZ is turned to 1000KHZ. Find: (i) Image frequency (ii) Local oscillator frequency

Last Answer : Given Intermediate Frequency fi=455KHz Signal frequency =fs=1000KHz Local oscillator frequency fo=fs+fi  Fo=1000KHz+455KHz  =1455KHz Image frequency is the input frequency which produces the same intermediate frequency fsi=fs+2fi  =1000KHz+2*455KHz  =1910KHz 

A super heterodyne AM receiver is tuned to a station operating at 1200 KHz .Find local oscillator frequency and image frequency.

Description : A super heterodyne AM receiver is tuned to a station operating at 1200 KHz .Find local oscillator frequency and image frequency.

Last Answer : A super heterodyne AM receiver is tuned to a station operating at 1200 KHz Intermediate frequency is 455KHz. IF frequency=f0-fs Local oscillator frequency is f0=IF +fs=455K+1200K=1655kHz The image frequency which gives the same IF is f0+2*IF=2110KHz

Define stub. Explain single and double stub in brief with neat sketch.

Description : Define stub. Explain single and double stub in brief with neat sketch.

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. 

Define critical frequency w.r. to wave propagation.

Description : Define critical frequency w.r. to wave propagation.

Last Answer : Define critical frequency w.r. to wave propagation.

Define: 1)Frequency 2)Bandwidth 3)Wavelength 4)Time period

Description : Define: 1)Frequency 2)Bandwidth 3)Wavelength 4)Time period

Last Answer : Frequency: Frequency is the number of cycles per second. Bandwidth: A range of frequencies within a given band, in particular that used for transmitting a signal. Wavelength: Wavelength can be defined as ... for one complete cycle of vibration to pass a given point.  OR Time period=1/frequency

Define the terms: 1) Maximum usable frequency 2) Fading

Description : Define the terms: 1) Maximum usable frequency 2) Fading

Last Answer : 1)Maximum usable frequency:- Maximum usable frequency is defined as the limiting frequency ,when the angle of incidence is other than the normal . OR The highest frequency that can be used for sky ... which left the same source but arrived at the destination by different paths is known as fading.

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.

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.

A telephone cable has following primary constants per loop kilometer ,R=30Ω, L=20mH,C=0.06µF,G=0.If the applied signal has an angular frequency of 5000 rad/sec.., Determine (i) Characteristics impedence (ii) Attenuation constant

Description : A telephone cable has following primary constants per loop kilometer ,R=30Ω, L=20mH,C=0.06µF,G=0.If the applied signal has an angular frequency of 5000 rad/sec.., Determine (i) Characteristics impedence (ii) Attenuation constant

Last Answer : A telephone cable has following primary constants per loop kilometer ,R=30Ω, L=20mH,C=0.06µF,G=0.If the applied signal has an angular frequency of 5000 rad/sec.., Determine (i) Characteristics impedence (ii) Attenuation constant

Compare ground wave and space wave propagation on the basis of: (i) Frequency range (ii) Method of propagation.

Description : Compare ground wave and space wave propagation on the basis of: (i) Frequency range (ii) Method of propagation.

Last Answer : Compare ground wave and space wave propagation on the basis of: (i) Frequency range (ii) Method of propagation.

Define the following terms related to antennas; (i) Antenna resistance (ii) Directivity (iii) Antenna gain (iv) Power density

Description : Define the following terms related to antennas; (i) Antenna resistance (ii) Directivity (iii) Antenna gain (iv) Power density

Last Answer : Antenna Resistance - The resistance of an antenna has two components: 1. Its radiation resistance due to conversion of power into electromagnetic waves 2. The resistance due to actual losses in the ... the transmitter power divided by the surface area of a sphere (4πR2) at that distance.

Define the following terms: (i) Polarization (ii) Antenna gain (iii)Antenna resistance (iv)Directivity

Description : Define the following terms: (i) Polarization (ii) Antenna gain (iii)Antenna resistance (iv)Directivity

Last Answer : i) Polarization:- It is defined as the direction of electric field vector in the EM wave radiated by the transmitting antenna. ii) Antenna Gain:- Antenna gain is defined as the ratio of ... in only one direction in which the radiation is maximum. That is directivity = Max. directive gain

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

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.  

Differentiate between single stub and double stub

Description : Differentiate between single stub and double stub

Last Answer : Differentiate between single stub and double stub

Why should local oscillator frequency be greater than signal frequency in AM receiver? Also explain why IF has constant value?

Description : Why should local oscillator frequency be greater than signal frequency in AM receiver? Also explain why IF has constant value?

Last Answer : Reason for LO frequency to be greater than signal frequency The local oscillator frequency (f0) is made greater than signal frequency (Fs) in radio receiver: Local oscillator frequency range is 995 ... frequency of desired signal because the IF is constant and same for all the incoming RF signal.

State the IF frequency and bandwidth of FM receiver.

Description : State the IF frequency and bandwidth of FM receiver.

Last Answer : IF for FM receiver: 10.7 MHz. Bandwidth of FM receiver:88MHz to 108 MHz

State the frequency range for audio frequency and voice frequency.

Description : State the frequency range for audio frequency and voice frequency.

Last Answer : The generally accepted standard range of audible frequencies is 20 to 20,000 Hz, The usable voice frequency band ranges from approximately 300 Hz to 3400 Hz.

Explain any four different frequency bands and give their two applications of each.

Description : Explain any four different frequency bands and give their two applications of each.

Last Answer : Explain any four different frequency bands and give their two applications of each.

Write down different frequencies for following(frequency ranges). (1) Voice frequency (2) High frequency (3) IR frequency (4) Visible frequency(light)

Description : Write down different frequencies for following(frequency ranges). (1) Voice frequency (2) High frequency (3) IR frequency (4) Visible frequency(light)

Last Answer : Sr. No Frequency Range 1 Voice Frequency 300 Hz to 3kHz 2 High Frequency  3 MHz to 30 MHz 3 IR Frequency 30 THz to 430 THz 4 Visible Spectrum (light) 375 THz to 750 THz

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

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

Last Answer : AM in Time domain  AM in frequency domain

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

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-  

Define VSWR with refernce to standing waves.

Description : Define VSWR with refernce to standing waves.

Last Answer : Voltage Standing Wave Ratio: The voltage standing wave ratio (VSWR) is the ratio of max voltage to min voltage. VSWR= VMAX /VMIN

Define sensitivity with graph.

Description : Define sensitivity with graph.

Last Answer : Define sensitivity with graph.

Define PAM, PWM, and PPM. Draw waveforms.

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.

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

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:

State the types of electromagnetic polarization? Define any one of it.

Description : State the types of electromagnetic polarization? Define any one of it.

Last Answer : Transverse electromagnetic wave:- The polarization of a plane EM wave is simply the orientation of the electric field vector with respect to the surface (i.e. looking at the horizon) If ... the field strength varies with change in polarization the wave is said to have an elliptical polarization 

Define modulation? State the desirable value of modulation index of AM.

Description : Define modulation? State the desirable value of modulation index of AM.

Last Answer : Modulation: It is the process in which any of these Parameters (Amplitude, Frequency, Phase) of high frequency signal (carrier signal) are varied in accordance with low frequency signal(modulating signal) For an AM, modulation index range is 0 to 1.

Define fading? List the causes.

Description : Define fading? List the causes.

Last Answer : The fluctuation in signal strength at a receiver, which is mainly due to the interference of two waves which left the same source but arrived at the destination by different paths, is known ... , such as irrigation, or from multiple transmission paths, irregular earth surfaces, and varying terrains.

Define electromagnetic wave and polarization.

Description : Define electromagnetic wave and polarization.

Last Answer : Electromagnetic wave:-An electromagnetic wave such as light consists of a coupled oscillating electric field and magnetic field which are always perpendicular; by convention Polarization:-polarization" of electromagnetic waves refers to the direction of the electric field.

Define the term baluns and explain where is it used?

Description : Define the term baluns and explain where is it used?

Last Answer : A type of electrical transformer used to connect an unbalanced circuit to a balanced oneORA balun is a type of transformer: it's used to convert an unbalanced signal to a balanced ... :- In audio applications, baluns convert between high-impedance unbalanced and low impedance balanced lines.

Define selectivity and sensitivity of AM Receiver.

Description : Define selectivity and sensitivity of AM Receiver. 

Last Answer : Selectivity:-It needs to accept signals of the wanted frequency and reject other unwanted frequencies. Sensitivity:-The sensitivity of a radio receiver is its ability to amplify weak signals. It is ... the receiver input terminals to give a standard output power, measured at the output terminals. 

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

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 

Define pulse modulation. State its types.

Description : Define pulse modulation. State its types. 

Last Answer : Pulse Modulation - consists essentially of sampling analog information signals and then converting those samples into discrete pulses. OR It consists essentially of sampling analog information signals and then converting those ... PAM - PWM - PPM  ii) Digital Pulse Modulation - PCM - DM - ADM 

Define modulation index in FM. What is maximum value of deviation ratio.

Description : Define modulation index in FM. What is maximum value of deviation ratio.

Last Answer : Modulation Index of FM: It is defined as the ratio of Frequency Deviation (δ) to the modulating signal frequency (fm). (OR)  

Define standing wave ratio.

Description : Define standing wave ratio. 

Last Answer : Standing wave ratio is defined as the ratio of maximum voltage (Vmax) to minimum voltage (Vmin). Standing wave ratio is also defined as the ratio of maximum current (Imax) to minimum current (Imin).

Define modulation index in AM and give its formula.

Description : Define modulation index in AM and give its formula.

Last Answer : In AM wave, the modulation index (m) is defined as the ratio of the amplitude of the modulating signal (Vm ) to the amplitude of carrier signal (Vc). m = Vm / Vc

Define: Base band signal with one example.

Description : Define: Base band signal with one example.

Last Answer : The electrical equivalent of the original information signal is known as the Baseband signal. Example:-The information or the input signal to a communication system can be analog i.e., sound, picture or it can be digital e.g. the computer data.

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

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

Compare PAM, PWM, and PPM on the basis of i. Variable characteristics ii. Bandwidth iii. Information contained in iv. Transmitted power

Description : Compare PAM, PWM, and PPM on the basis of i. Variable characteristics ii. Bandwidth iii. Information contained in iv. Transmitted power

Last Answer : Compare PAM, PWM, and PPM on the basis of i. Variable characteristics ii. Bandwidth iii. Information contained in iv. Transmitted power

Write one application of following antenna i. Rectangular antenna ii. Dish antenna iii. Yagi-Uda antenna iv. Horn antenna

Description : Write one application of following antenna i. Rectangular antenna ii. Dish antenna iii. Yagi-Uda antenna iv. Horn antenna 

Last Answer : i. Rectangular antenna is used in direction finding in portable recievers. ii. Dish antenna is used to transmit and receive signal from satellite. iii. Yagi-Uda antenna is used in HF and VHF range as a TV receiving antenna. iv. Horn antenna is used in satellite tracking.

a) For a transmission line, Find SWR and reflection coefficient R if, i. There is no reflected voltage. ii. Reflected voltage and incident voltage is equal. iii. If reflected voltage=20V and incident voltage=10V. iv. If reflected voltage=10V and incident voltage =20V.

Description : a) For a transmission line, Find SWR and reflection coefficient R if, i. There is no reflected voltage. ii. Reflected voltage and incident voltage is equal. iii. If reflected voltage=20V and incident voltage=10V. iv. If reflected voltage=10V and incident voltage =20V.

Last Answer : reflection coefficient R=Vr/Vi i. There is no reflected voltage. i.e,Vr=0 R=0 SWR= 1+R/1-R=1 ii. Reflected voltage and incident voltage is equal. Vr=Vi; R=1 SWR= 1+R/1-R=1+1/1-1=infinity iii. If reflected ... and incident voltage =20V. Vr=10 and Vi=20 R=10/20=0.5 SWR= 1+R/1-R=1+.5/1-.5=3 

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

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 

Describe with respect to antenna (i) radiation pattern (ii) directive gain (iii) power gam (iv) polarization

Description : Describe with respect to antenna (i) radiation pattern (ii) directive gain (iii) power gam (iv) polarization

Last Answer : (i) Radiation pattern:-A graph or diagram which tells us about the manner in which an antenna radiates more power in different directions is known as the radiation patteren of antenna.  ( ... as the direction of the electric vector in the electromagnetic wave radiated by the transmitting antenna. 

Differentiate between AM and FM on the basis of: (i) Definition (ii) Bandwidth (iii) Modulation Index (iv) Application

Description : Differentiate between AM and FM on the basis of: (i) Definition (ii) Bandwidth (iii) Modulation Index (iv) Application

Last Answer : Compare AM and FM on the basis of i)Definition ii)Bandwidth iii) Wave propogation iv)Number of sidebands

Explain the following characteristics of AM radio receiver: (i) Sensitivity (ii) Selectivity.

Description : Explain the following characteristics of AM radio receiver: (i) Sensitivity (ii) Selectivity.

Last Answer : Sensitivity:- The ability to amplify the weak signals is called sensitivity. It is the function of overall receiver gain. Sensitivity of radio receiver is decided by the gain of the RF IF ... perfectly the receiver is able to select the desired carrier frequency and reject other frequencies. 

For AM, fc =500kHz , fm = 5 kHz Determine: (i) Upper and lower sideband frequencies (ii) Bandwidth

Description : For AM, fc =500kHz , fm = 5 kHz Determine: (i) Upper and lower sideband frequencies (ii) Bandwidth

Last Answer : Given data fc = 500KHz , fm = 5KHz USB =fc+fm USB = 500+5  =505 KHz. LSB =fc – fm LSB = 500 – 5  =495 KHz Bandwidth = 2fm .  = 2* 5 =10 KHz

For a transmission line, the incident voltage. Ei = 6V and Er =2V ,Calculate: (i) Reflection Coefficient (ii) SWR

Description : For a transmission line, the incident voltage. Ei = 6V and Er =2V ,Calculate: (i) Reflection Coefficient (ii) SWR

Last Answer : Reflection Coefficient(K) = Er / Ei  = 2V / 6V  K = 0.333 SWR = 1+K / 1- K  = 1+0.333 / 1-0.333  = 1.333 / 0.667 SWR= 1.998

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

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.

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

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.

Draw and label the circuit diagram of ratio detector

Description : Draw and label the circuit diagram of ratio detector 

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

Calculate the characteristics impedance for a transmission line having L=0.5 mH/Km, C=0.08 µF and negligible R and G.

Description : Calculate the characteristics impedance for a transmission line having L=0.5 mH/Km, C=0.08 µF and negligible R and G.

Last Answer : L=0.5 mH/Km C=0.08 µF