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147 Cards in this Set
- Front
- Back
What is the accuracy of a gps fix with selective availability turned on?
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100 metters 95% of the time
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What is the probable cause for a docked vessel to occasionally register speed and direction on a gps reciever?
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A normail condition caused by Department of Defense selective availability
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Why does the received signal from a satellite, stabilized by a computer-pulsed electromagnet, exhibit a fairly rapid pulsed fading effect?
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because the satellite is rotating
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Solder most commonly used for hand soldering in electronic is?
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60% tin 40% lead
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Which of the following is an acceptable method of solder removal from holes in a printed board?
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Soldering iron and a suction device
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The ideal method of removing insulation from wire is?
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The thermal stripper
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Why do we tin component leads?
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Decreases heating time and aids in connection
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What is the purpose of using a small amount of solder on the tip of a soldering iron just prior to making a connection?
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Aids in wetting the wires
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What occurs if the load is removed from an operating series DC motor?
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It will accelerate utill if flies apart
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Why are concentric transmission lines sometimes filled with nitrogen?
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Keep moisture out and prevent oxidation
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Nitrogen is place in tranmission lines to?
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Prevent moisture from entering the line
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How much farther does the radio-path horizon distance exceed the geomtric horizon?
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By approximately 15% of the distance
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What is a knife-edge diffraction?
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Allows normally line of sight signals to bend around sharp edges, mountain ridges, buildings and other obstructures
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The bending of radio waves passing over the top of a mountain range that disperses a weak portion of the signal behind the mountain is?
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knife-edge diffraction
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If the elapsed time for a radar echo is 62 microseconds what is the distance in nautical miles to the object?
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5 nautical miles
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What is the waveleghth of a signal at 500 MHz?
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60 cm.
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The radar range in nautical miles to an object can be found by measuring the elapsed time during a radar pulse and dividing this quantity by?
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12.36 microseconds.
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If a transmitting antenna is 100 meters high and a separate receiving antenna is 64 meters high, what is the maximum space wave communication distance possible between them?
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72km
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Ducts often form over?
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Water
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What is a frequency standard?
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A device used to produce a highly accurate reference frequency.
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What is the most that the actual transmit frequency could differ from a reading of 462,100,000- hertz on a frequency counter with a time base accuracy of +/- 0.1 ppm?
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46.21 Hz.
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How can even-order harmonics be reduced or prevented in transmitter amplifier design?
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by using a push pull amplifier
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Is a strong FM-phone signal and a weak FM-phone signal, both using the same carrier frequency, are received simultaneously, why is only one demodulated?
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Strong signal captures the local oscillator preventing the weak signal from being detected
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An electrical relay:
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Is a remotely controlled switching device.
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Which of the following navigational methods utilizes the lowest frequency for a carrier?
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omega
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When a vacuum tube operates at VHF or higher frequencies as compared to lower frequencies:
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Transit time of electrons becomes important
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The principle of omega navigation depends on measuring the _____ between received pulses.
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Phase angle
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What type of antenna system allows you to receive and transmit at the same time in both directions?
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Duplex
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A microwave device that allows RF energy to pass through in one direction with very little loss but absorbs RF power in the opposite direction?
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Isolator
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Which of the following is found in an improved mopa but not in a basic mopa?
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Buffer amplifier
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What is the characteristic of the current flow in a parallel R-L-C circuit at resonance?
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The current circulating in the parallel elements is at a maximum
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What factors determine the capacitance of a capacitor?
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Area of the plates, distance between the plates and the dielectric constant of the material between the plates
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Why would the rate at which electrical energy is used in a circuit be less than the product of the magnitudes of the AC voltage and current?
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Because there is a phase angle that is greater than zero between the current and voltage
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In a circuit where the AC voltage and current are out of phase, how can the true power be determined?
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By multiplying the apparent power times the power factor
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What is the photoconductive effect?
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The increased conductivity of an illuminated semiconductor junction
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What is the time constant of a circuit having two 100-microfared capacitors and two 470-kilohm resistors all in series?
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47 seconds
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What is the time constant of a circuit having two 220-microfared capacitors and two 1-megohm resistors all in parallel?
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220 seconds
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What is the time constant of a circuit having a 220-microfarad capacitor and a 470-kilohm resistor in series?
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103 seconds
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How long does it take for an initial charge of 20 V DC to decrease to 7.36 V DC in a .01 microfarad capacitor when a 2-megafarad resistor is connected across it?
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0.02 seconds
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How long does it take for an initial charge of 800 v dv to decrease to 108 v dc in a 450-microfarad capacitor when a 1-megohm resistor is connected across it?
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1350 seconds
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What is the impedance of a network composed of a 100-ohm reactance inductor in series with a 100- ohm resistor?
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141 ohms, /45
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What is the impedance of a network composed of a 400- ohm reactance inductor in parallel with a 300-ohm resistor?
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240 ohms, / 36.9
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What is the impedance of a network composed of a 1.0 millihenry inductor in series with a 200-ohm resistor, at 30kHz?
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200 + j188
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Which of the following components is used in a power supply circuit to allow filter capacitors to discharge when power is turned off and aids in holding the voltage output more constant?
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Bleeder resistor ohms
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A 1 watt, 10 volt zener diode with the following characteristics:1 min= 5ma, 1 max =95ma and z = 8ohms; is to be used as part of a voltage regulator. Approximately what size current limiting resistor would set its bias to the midpoint of its operating range?
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200 ohms.
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Given a power supply with a full load voltage of 200 volts and a regulation of 25%, what is the no load voltage?
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250 volts
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A transformer used to step down its input voltage must have?
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More turns of wire on its primary than on its secondary
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A power transformer has a 120 volt primary winding and a 24 volt secondary winding/ What is the turns ratio?
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1:5
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A 6 volt battery with 1.2 ohms internal resistance is connected across two 3 watt bulbs. What is the current flow?
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.83 amps
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If a marine radiotelephone receiver uses 75 watts of power and a transmitter uses 325 watts, how long can they both operate before discharging a 50 ampere-hour 12 volt battery?
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1 ½ hours
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How many capacitors of 400 volts and 2.0 microfarads each would be necessary to obtain a combination rated at 1600 volts and 1.5 microfarads?
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12
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What is the total impedance of a series AC circuit having a resistance of 6 ohms, an inductive reactance of 17 ohms, and zero capacitive reactance?
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18 ohms
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A 3 horsepower, 100 vdc motor is 85% efficient when developing its rated output. What is the current?
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26.3 amps
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The second harmonic of a 380 kHz frequency is?
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760 kHz
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In a self-biased RF amplifier stage: plate voltage= 1250 volts, plate current = 150 ma, grid current = 15 ma, and grid-leak resistance of 4000 ohms. What is the operating grid bias voltage?
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60 Volts
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What would be the dB change in field intensity at a given distance if the transmitter output power is doubled?
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1.5 dB
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If a field strength is 100 microvolts per meter at 100 miles, what is the field strength at 200 miles?
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50 microvolts
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What is the purpose of a multiplier resistor used with a voltmeter?
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Its is used to increase the voltage indicating range of the voltmeter.
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How much energy is used in a week by a 117 volt clock having an internal resistance of 5000 ohms?
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460 watt-hours
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If a complex circuit is reduced to an equivalent circuit consisting of a single voltage source in series with a single resistor, this is an example of?
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Thevenin’s theorem
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Which of the following would shield a permanent magnet field best?
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Iron
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If a 10 henry coil has 50 mS of current flowing through it, how much energy is stored in the magnetic field?
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0.0125 joules
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What is the capacitance of a capacitor with individual plate area of 2 square inches each, an air dielectric, and spacing between the two parallel plates of 0.01 inches?
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45 picofarads
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What is the range of voltage ratings available in Zener diodes?
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2.4 volts to 200 volts.
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What special type of diode is capable of both amplification and oscillation?
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Tunnel diodes
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What is a common use of a hot carrier diode?
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As VHF and UHF mixers and detectors
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When an SCR is in the triggered or on condition, its electrical characteristics are similar to what other solid state device?
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The junction diode
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What would be the bandwidth of a good crystal lattice bandpass filter for a single sideband phone emission?
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2.1 kHz at -6 dB.
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What would be the bandwidth of a good crystal lattice band pass filter for a double sideband phone emission?
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6 kHz at -6 dB
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What technique can be used to construct low cost, high performance crystal lattice filters?
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Etching and grinding
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What determines the bandwidth and response shape in a crystal lattice filter?
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Thte relative frequencies of the individual crystals
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Why do many MOSFET devices have built in gate protective zener diodes?
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The gate protective zener diode prevents the gate insulation from being punctured by small static charges or excessive voltages.
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How does the input impedance of a field effect transistor compare with that of a bipolar transistor?
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An FET has high input impedance; a bipolar transistor has low input impedance
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What do the initials TTL stand for?
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Transistor-Transistor logic
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What is the range of input voltages considered to be a logic low in a CMOS device operating with an 18 volt power supply?
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0.0 to 5.4 volts
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What is a CMOS IC?
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A chip with P-channel and N-channel transistors.
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Why do CMOS digital integrated circuits have high immunity to noise on the input signal or power supply?
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The input switching threshold is about one-half the power supply voltage.
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What type of diode contains no minority carriers in the junction region?
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Hot-carrier diode
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What conditions exist when a transistor is operating in saturation?
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The base emitter junction and collector base junction are both forward biased.
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Which of the following logic gates will provide an active high out when both inputs are active high?
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and
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An R-S flip flop is capable of doing all of the following except?
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operate in toggle mode with R-S inputs held constant and CLK initiated
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What class of amplifier is distinguished by the presence of output throughout the entire signal cycle and the input never goes into the cutoff region?
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Class A
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What class of amplifier is distinguished by the bias being set well beyond cutoff?
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Class C
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What is a Pi-L network?
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A network consisting of two inductors and two capacitors.
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How are networks able to transform one impedance to another?
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The matching network can cancel the reactive part of an impedance and change the value of the resistive part of an impedance.
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Why is the L-network of limited utility in impedance matching?
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It matches a small impedance range.
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What is an advantage of using a pi-L network instead of a Pi-network for impedance matching between the final amplifier of a vacuum tube type transmitter and a multiband antenna?
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Greater harmonic suppression.
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Which type of network provides the greatest harmonic suppression?
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Pi-L network.
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What are the distinguishing features of a butter worth filter?
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It has a maximally flat response over its passband.
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How is the positive feedback coupled to the input in a Pierce oscillator?
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Through capacitive coupling.
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What is the piezoelectric effect?
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Mechanical vibration of a crystal by the application of a voltage
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What is meant by the term modulation?
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A mixing process whereby information is imposed upon a carrier
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How is a G3E FM phone emission produced?
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With a reactance modulator on the oscillator
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How can a single sideband phone signal be generated?
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By using a balanced modulator followed by a filter
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How can parasitic oscillations be eliminated from a power amplifier?
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By neutralization
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What occurs in a receiver when an excessive amount of signal energy reaches the mixer circuit?
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Spurious mixer products are generated.
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How much gain should be used in the RF amplifier stage of a receiver?
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Sufficient gain to allow weak signals to overcome noise generated in the first mixer stage
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What is a flip flop circuit?
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A binary sequential logic element with two stable states.
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What is a bistable multivibrator circuit?
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A flip flop.
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How many output changes are obtained for every two trigger pulses applied to the input of a bistable t flip flop circuit?
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Two output level changes
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What is a AND gate?
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A circuit that produces a logic 1 at its output only if all inputs are logic 1.
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What is a NAND gate?
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A circuit that produces a logic 0 at its output only when all inputs are logic 1.
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What is a crystal controlled marker generator?
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A high stability oscillator that generates a series of reference signals at known frequency intervals.
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What additional circuitry is required in a 100 khz crystal contolled marker generator to provide markers at 50 and 25 khz?
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Two flip flops
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What are the advantages of using an op amp instead of LC elements in an audio filter?
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Op amps exhibit gain rather than insertion loss.
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What are the principle uses of an op amp RC active filter?
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Op amp circuits are used as audio filters for receivers
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How can unwanted ringing and audio instability be prevented in a multisection op amp RC audio filter cirvuit?
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Restrict both gain and Q.
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What parameter much be selected when designing an audio filter using an op amp?
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Bandpass characteristics
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What is the theoretical minimum noise floor of a receiver with a 400 hertz bandwidth
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148 dbm
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What is meant by the dynamic range of a communications receiver?
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The ratio between the minimum discernible signal and the largest tolerable signal without causing audible distortion products
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What is emission A3F?
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Television
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What is the deviation ratio for an FM phone signal having a maximum frequency swing of plus or minus 5 kHz and accepting a maximum modulation rate of 3 kHz?
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1.66
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What is the deviation ratio of a FM phone signal having a maximum frequency swing of plus or minus 7.5 kHz and accepting a maximum modulation rate of 3.5 kHz?
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2.14
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What is the modulation index of an FM phone transmitter producing an instantaneous carrier deviation of 6 kHz when modulated with a 2 kHz modulating frequency?
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3
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What are electromagnetic waves?
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A wave consisting of an electric field and a magnetic field at right angles to each other.
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If a sine wave begins from above or below the zero axis, how many times will it cross the zero axis in one complete cycle?
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2 times.
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What is a square wave?
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A wave that abruptly changes back and forth between two voltage levels and which remains an equal time at each level.
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What type of wave is made up of sine waves ofthe fundamental frequency and all the odd harmonics?
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Square wave
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Which sine waves make up a sawtooth wave?
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The fundamental frequency and all harmonics.
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What is the RMS voltage at a common household electrical power outlet?
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117-V AC
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For many types of voices, what is the ratio of PEP to average power during a modulation peak in a single sideband phone signal?
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about 2.5 to 1
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What is the approximate DC input power to a Class B rf power amplifier stage in an FM phone transmitter when the PEP output power is 1500 watts?
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Approximately 2500 watts.
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Why is the transmitter peak power in a plulse modulation system much greater than its average power?
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The signal duty cycle is less than 100%
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What is the necessary bandwidth ofa 170 hertz shift, 45 baud baudot emission f1b transmission?
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249 Hz
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What is the purpose ofa pilot tone in an amplitude compoandored sigle sideband system?
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It permits rapid tuning of amobile receiver.
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What is the frequency range of the marker beacon systme used to indicate an aircraft's position during an ils approach to an airports runway?
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The outer, the middle, and the inner marker beacon's carrier frequencies are all 75 MHz but the marker beacons are 95% tone modulated at 400 Hz,1300Hz, 3000Hz
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What is the frequency range of the distance measuring equipment used to indicate an aircrafts slant range distance to a selected ground based navigation station?
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962 MHz to 1213 MHz
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What are the transmission and the reception frequencies of an aircrafts mode C transponder operating in the Air traffic control radar beacon system?
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Tranmit at 1090 Mhz and receive at 1030 MHz
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What type of encoding is used in an aircraft's mode C transponder transmission to a ground station of the air traffic control radar beacon system?
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Pulse position modulation.
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How does the bandwidth of a folded dipole antenna compare with that of a simple dipole antenna?
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It is greater
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What is the physicallength of a twen lead transmission feedline at 36.5 Mhz?
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Electrical length times 0.8
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Why should an HF mobile antenna loading coil have a high ratio of reactance to resistance?
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To minimize losses
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How much gain does a 1/2 wavelength dipole have over an isotropic radiator?
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2.1 db
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What factors determine trhe receiving antenna gain required at a station in earth operation?
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Height, transmitter power and antennas of satellite.
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What is the beamwidth of a symmetrical pattern antenna with a gain of 20 db as compared to an isotropic radiator?
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20.3 degrees.
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What term describes a method of antenna impedance matching that uses a short section of transmission line connected to the antenna feed line near the antenna and perpendicular to the feed line?
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The stub matching system.
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Adding parasitic elements to an antenna will?
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Increase its directional characteristics
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What ferrite rod device prevents the formation of reflected waves on a waveguid transmission line?
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Isolator
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Frequencias most affected by knife edge refraction are?
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Very high and ultra high frequencies.
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What is the pursose of stacking elements on an antenna?
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All of the above
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What type of antenna is used in an aircrafts ils marker beacon installation?
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A balanced loop reception antenna
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Nitrogen gas in concentric RF transmission lines is used to ?
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keep moisture out and prevent oxidation.
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"stacking" elements on an antenna?
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Makes for better reception
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What type of antenna radiates the 1030 MHz interrogation signals from anaircrafts Mode S traffic alert and Collision Avoidance System installation?
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An electronically steerable phased array directional antenna
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Waveguides are:
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Hollow metal conductors used to carry hitgh frequency current.
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Concerning shunt-fed 1/4 wavelength Marconi antenna:
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DC resistance ofthe antenna to ground is zero.
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What type of antenna pattern is radiated from a phased array directional antenna when transmitting the P2 side bobe suppression pulse in a Mode S interrogation signal of an aircraft's traffic alert and Collision Avoidance System installation?
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A 1030 Mhz omnidirectional pattern.
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