Which

of the following is not a major communications medium? a. b. c. d. Fiber Optic Water Wires Free space

In a resonant circuit, a new inductor whose value is twice as high replaced the original inductor, what happens to the frequency in which the network will resonate? a. b. c. d. it will increase by a factor of 0.707. it will decrease by a factor of 2 it will decrease by a factor of 0.707 it will decrease by a factor of 0.956

for a given bandwidth signal, more channel space is available in the range of a. b. c. d. SHF UHF EHF VHF

What value of the series resistor is needed for a pi-pad to provide a loss of 20dB if it will be inserted in a network whose impedance is 100 ohms? a. b. c. d. 150 ohms 495 ohms 400 ohms 122 ohms

a bridged-H pad is an example of a. b. c. d. Asymmetrical, balanced Symmetrical, unbalanced Symmetrical, balanced Asymmetrical, unbalanced

What is the output voltage of a RC LPF whose R = 10kohms and C = 1 nF if a 100mVpk input signal has a frequency of 15kHz? a. b. c. d. 58.59 mVpk 72.77 mVpk 68.59 mVpk none of the above

a series resonant circuit has the following parameters: R = 5ohms, L = 5micro Henry, C = 5nF with a 5V ac input. What is the impedance at 100kHz above resonance? a. 4+j5 ohms b. 6+j7 ohms c. 10+j12 ohms

d. 5+j6 ohms A passive low pass filter having a cut-off of 15kHz will need what capacitance value if the resistance is equal to 1 kHz? a. b. c. d. 66.67 nF * 45.61 nF 10.61 nF 5.3 nF

The Q of a tuned circuit was improved, what happens to the bandwidth? a. b. c. d. widened increased not affected narrowed

The visible light with the shortest wavelength is a. b. c. d. Yellow Green Violet Red

What characteristic of the network implies that the output and input impedances are equal to the characteristic impedance a. b. c. d. it is asymmetrical it is in the first order it is symmetrical it is a pi network

Amplifier usually found at the last stage a. b. c. d. Darlington pair Buffer Driver Emitter follower

Three modulating signals, with index rations 3:4:5 modulate a 200kHaz carrier signal. The modulated AM has a total modulation depth of 70.7%. The individual indexes of the modulating signals are a. b. c. d. 0.60, 0.80, and 1.0 0.30, 0.40, and 0.50 0.450, 0.60, and 0.75 0.45, 0.80, and 1.0

What is the value of the image frequency of an FM broadcast-band receiver if the desired receive frequency is 107.5 MHz? (assume high-side injection)

a. b. c. d.

86.1MHz 96.8MHz 118.2MHz 128.9MHz

An AM transmitter has 50 kW unmodulated carrier, if the index is 0.75, how much of the transmitted power contains information? a. b. c. d. 17.06 kW 7.03 kW 15.06 kW 25 kW

How much power is saved if J3E is used instead of A3E at 90% modulation? a. b. c. d. 28.82% 85.59% 87.11% 14.41%

Which of the following is true if m is greater than 1? a. b. c. d. normal operation carrier drops to zero information signal is distorted carrier frequency shifts

how is IFRR improved? a. b. c. d. increase frequency of signal increase frequency of IF increase frequency of LO increase frequency of BB

in the phasing method of SSB generation, one sideband is cancelled out due to a. b. c. d. phase inversion balanced modulator phase shift carrier suppression

what is the local oscillator frequency of a receiving tuned to DZMM? a. b. c. d. 455 kHz 1121 kHz 1085 kHz 1075 kHz

information in an AM signal is conveyed in the a. carrier and sidebands b. envelope c. sideband

d. carrier which of the following is not true about AM? a. b. c. d. Ec must always equal Em Em should be equal to or less than EC Em should be greater than EC Ec should be greater than Em

A form of AM signal which is used for TV picture transmission a. b. c. d. F3F B8E C3F A3E

What does a balanced modulator do? a. b. c. d. it produces DSBSC signal it produces DSBFC signal it produces SSBFC signal it produces SSBSC signal

An FB BC station operates with a peak-to-peak deviation equal to 120kHz. Calculate the percentage modulation. a. b. c. d. 75% 80%? 100% 50%

in an FM signal,, FM is a 1.5kHz. the carrier frequency is 1000kHz, the frequencies of the third significant sidebands are a. b. c. d. cannot be determined 1.0045MHz and 9995.5kHz frequency of the modulating signal 1.0015 MHz and 998.5kHz

A 5 V tone would result to a 20kHz deviation, what about a 7.5V tone? a. b. c. d. 30kHz 20kHz 80kHz 40kHz

In FM, the amplitude of the modulating voltage is doubled, the maximum frequency deviation a. b. c. d. Becomes four times Remains unaltered Doubles Becomes half

In FM, if the frequency of the modulating signal is doubled, the maximum frequency deviation a. b. c. d. doubles becomes half becomes four times remains unaltered

In FM, if the frequency of the modulating signal is doubled, the rate of deviation of the carrier frequency a. b. c. d. becomes half becomes four times remains unaltered doubles

in FM, the carrier frequency deviation is determined by a. b. c. d. modulating voltage modulating frequency carrier frequency none of the above

deviation ratio allowed for sound signal in TV broadcasting a. b. c. d. 1 1.67 3 33

This is interference due to single tone or complex periodic waveform a. b. c. d. insertion harmonic distortion tone interference inter-modulation distortion

The practical bandwidth of a narrowband FM signal (maximum deviation <1) is a. b. c. d. FM Maximum deviation Twice the maximum deviation 2fm

the ideal noise figure is a. b. c. d. Unity Infinity None of the choices 0

a kind of distortion due to sum and difference of signals entering a non linear device

a. b. c. d.

harmonic amplitude distortion intra-modulation distortion inter-modulation distortion

What is a preselector a. b. c. d. Tuned circuit before the mixer The first to select The receiving antenna of the system Tuned circuit before the demodulator

The most efficient form of AM in terms of power utilization a. b. c. d. J3E A3E H3E R3E

What is the major advantage of a superheterodyne receiver over tuned radio frequency receiver? a. b. c. d. Good sensitivity Good selectivity ? Simple circuitry All of the above

One of the main functions of the RF amplifier in a superheterodyne receiver is to a. b. c. d. provide improved tracking permit better adjacent channel rejection increase the tuning range of the receiver improve the rejection of the image frequency

indicate the false statement. The superheterodyne receiver replaced the TRF receiver because the latter suffered from a. b. c. d. gain variation over the frequency coverage range. Insufficient gain and sensitivity Inadequate selectivity at high frequencies Instability

A superheterodyne receiver is tuned to a frequency of 5MHz when the oscillator frequency of 5Mhz when the oscillator frequency is 6.65 MHz. What is the IF a. b. c. d. 0.65 MHz 1.65 MHz 5 MHz 11.55MHz

intermediate frequency for an AM broadcasting system as per FCC rules a. 155 kHz

b. 255 kHz c. 355 kHz d. 455 kHz What parameter enables a receiver to detect the weakest possible signal level? a. b. c. d. sensitivity selectivity fidelity dynamic range

A superheterodyne receiver with an IF of 450 kHz is tuned to a signal at 1200 kHz. The image frequency is a. b. c. d. 750 kHz 900 kHz 1650 kHz 210 kHz --- 1200+2(450)

what is the local oscillator frequency needed in the previous problem to produce an IF of 450kHz a. b. c. d. 1650 kHz -> 1200 + 450 750 kHz 900 kHz 2100 kHz

Which section of a superheterodyne receiver converts the IF signal back to the original source information? a. b. c. d. RF section Mixer IF section Detector

Most of the gain and selectivity in a superheterodyne receiver is obtained in the a. b. c. d. RF Section IF Section ? Mixer Detector

Determine the IF bandwidth necessary to achieve a bandwidth improvement of 16dB for a radio receiver with an RF bandwidth of 320kHz a. b. c. d. 8 kHz ? 20 kHz 50 Hz 304 kHz

it is a measure of the extent to which the carrier is varied by the intelligence a. Bandwidth

b. Shape factor c. Bandwidth Improvement d. Modulation factor Which is true about over modulation? a. b. c. d. modulating voltage is less than carrier voltage modulating voltage is equal to the carrier voltage overmodulation procudes a distortion at the demodulated ouput none of the choices

A sine wave carrier is modulated by a single tone so that Emax = 18mV and Emin = 0mV. Calculate the modulation index when the unmodulated carrier is 6 mVpk- pk. a. b. c. d. 0.667 1.0 2 None of the choices

The modulation index of an AM wave is changed from 0 to 1, the transmitted power is a. b. c. d. unchanged halved doubled increased by 50%

The percentage of modulation for maximum amplitude of information transmission is ___ % a. b. c. d. 0 50 75 100

An AM wave has a modulation factor of 0.9, and an unmodulated carrier amplitude of 10V, what is the amplitude of the lower sideband signal? a. b. c. d. 10 5 9 4.5 V

Three tones 5V 10kHz, 7.5V 3kHz and 15V 5kHz modulate a 20V carrier. Compute for the percentage modulation a. 83.33 b. 45.83 c. 57.50 d. 87.50 the total sideband power is what percentage of the carrier power in DSBFC AM?

a. b. c. d.

50 33.33 16.67 66.67

An antenna transmits an AM signal having a total power conrtent of 15kW. Determine the power being transmitted at each of the sidebands when the percent modulation is 85%. a. b. c. d. 11019W 1990W PLSB = PUSB - PC 3981W 1019W

An AM transmitter is modulated by two sine waves at 1kHz and 2.5 kHz with modulations of 25% and 50 % respectively. What is the effective modulation index? a. b. c. d. 0.58 0.65 0.75 0.25

Determine the modulation factor if a second modulating tone having twice the amplitude of the first, but different frequency is added at the input of the modulator for simultaneous modulation. a. b. c. d. 1.73 1.4 2 2.24

A 2000 Hz audio signal having an amplitude of 15 V modulates a 100 kHz carrier which has a peak value of 25 Vwhen not modulated. Calculate the modulation factor of the modulated wave a. b. c. d. 0.4 0.5 0.6 = 15/25 0.7

In the previous problem, what frequencies would show up in a spectrum analysis of the AM wave? a. b. c. d. 98kHz, 100kHz, 102kHz 90.8kHz, 100kHz, 102.8kHz 98.8kHz 100kHz, 102.8kHz 198kHz, 200kHz, 202kHz

what is the required bandwidth necessary to transmit the AM signal in the previous problem? a. 2kHz

b. 4kHz c. 200kHz d. none of the choices A bandwidth of 12 MHz becomes available for assignment. If assigned for TV broadcast service, only the two channels could be accommodated. Determine the number of AM stations that could be broadcast simultaneously if the maximum modulating frequency is limited to 5 kHz a. b. c. d. 1000 1200 800 1600

Anticipating single sideband AM, what percentage of total pwer is saved by suppressing the carrier and one set of sidebands while transmitting the other set of sidebands only for m=0.75? a. b. c. d. 66.7 % 89 % 100 % 45 %

Which circuit produces a suppressed carrier signal? a. b. c. d. Mixer Low pass filter Tuned circuit Balanced modulator

Which of the following is not true about single sidebands transmission? a. b. c. d. SSB transmission saves power It occupies less bandwidth More expensive ? All of the above ?

If the carrier of a 100% modulated AM wave is suppressed, the percentage power saving will be a. b. c. d. 50 150 100 66.66

An AM wave has a total transmitted power of 4kW when modulated 85%. How much total power should an SSB wave contain in order to have the same content as the contained in the two sidebands? a. b. c. d. 1061.5 W? 530.76 W? 2120 W 2938.5

If a transmitter power of 100 W is sufficient for reliable communication over a certain path using SSB, approximately what power level would be required using DSB? a. b. c. d. 300 W 600 W 100 W 200 W

In the previous problem, what is the power required for full-carrier AM. a. b. c. d. 600 W 100 W 200 W 800 W

CB radios was developed using full carrier DSB AM. It operates using 40 channels, each 10 kHz wide. When SSBSC is used, the same carrier frequencies are used as with conventional AM, but the transceivers are switchable to either lower or upper sideband. How many channels are available when SSB used? a. b. c. d. 40 60 80 120

A modulator circuit performs what mathematical operation on its two inputs? a. b. c. d. addition multiplication division subtraction

one of the following cannot be used to remove the unwanted sideband in SSB. This is the a. b. c. d. Filter system Phase shift method Detector Balanced modulator

An audio signal with 0.5kHz range and a carrier signal with 100kHz frequency are mixed together in a balanced modulator. Which of the following frequencies cannot be found at the output of the modulator? a. b. c. d. 100kHz 105kHz 95kHz none of the choices

To provide two or more voice circuits with the same carrier, it is necessary to use

a. ISB b. Carrier reinsertion c. SSB with pilot carrier d. Lincompex An AM receiver uses a diode detector for demodulation. This enables it satisfactorily to receive a. b. c. d. SSBSC SSB reduced carrier ISB SSBFC