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147 Cards in this Set

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