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What is defined as "Most widely used system of units, both in science & everyday commerce"
International System of Units (SI)
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What is a decibel (dB) used for in relation to EW?
to express the ratio of two power levels.
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Explain the SI prefix for each whole number.
- 1 trillion (1012) - Tera
- 1 billion (109) - Giga
- 1 Million (106) - Mega
- 1 Thousand (103) - Kilo
- .001 (10-3) - Mila
- .000001 (10-6) micro
- .000000001 (10-9) nano
- .000000000001 (10-12) Peca
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What is the formula for determining the dB difference between two power ratios?
dB=(P2/P1)logx10
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To effectively jam a signal what must the power be?
3 dB higher or 2x as strong
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Name the 3 parts of an atom and their charges?
- Electron- negative charge
- Proton - Positive charge
- Neutron - no charge
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What are the 6 methods to can create voltage?
- Fricton
- Magnetism
- Heat
- Pressure
- Light
- Chemical
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What are the two forms of energy?
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Energy contained in an object due to its motion is _____ energy.
Kinetic
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Energy contained in an object due to its position is ____ energy.
Potential
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What is the process by which an atom gains or loses electrons?
Ionization
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What is a material that is good at allowing electricity to flow through it?
conductor
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What is defined as "extremely high resistance to the flow of electricity"?
Insulator
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what is defined as "all matter between the extremes of conductors and insulators"?
Semi-conductor
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What does P,I,E and R represent on the Ohms law pie chart?
- P - Watts (power)
- I- Amps (current)
- E - Volts
- R - Ohms (Resistance)
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In the formula dB = (P2/P1)log x 10 what does P1 and P2 represent?
- P1 = Target / Input
- P2 = Effect / Output
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What is defined as "Determined by the direction of the lines of force making up the electric field"?
Polarization
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This propagates in all directions
Omni-directional
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This propagates in a specific direction while minimizing propagation in other directions
Directional
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Defined as "an antenna built for transmitting a certain signal is equally good at receiving that same signal"?
Reciprocity
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This is defined as "the number of waves that pass a fixed place in a given amount of time"
Frequency
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Time it takes for the completion, from any given point of a wave to the same point on the next wave.
Cycle
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The distance between repeating units of a wave, usually measured in meters?
Wavelength
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Highest point of a wave
Crest or peak
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Lowest point of a wave
Trough
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Defined as "height of a sine wave measured in peak or peak-to-peak"
Amplitude
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Defined as "movement through a medium"
Propagation
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What are the three layers of the Earth's atmosphere?
- Troposphere (0-16 miles)
- Stratosphere (16-30)
- Ionosphere (30-300)
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Defined as "Bouncing off on substance to extend the range of a radio wave"?
Reflection
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Defined as "Radio wave bending as they move from one medium to another"?
Refraction
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This is when a radio wave "bends" around an object.
Diffraction
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What factors affect Ionosphere refraction?
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Explain the relationship between the wavelength and the frequency of the EM spectrum.
- Inversely Proportional
- High Freq = Short WL
- Low Freq = Long WL
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SI is composed of what?
Base units and prefix
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A negative ion has ____ than its normal amount of electrons.
more
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a positive ion has ___ than its normal amount of electrons.
less
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Defined as "the process by which an atom gains or loses its electrons".
Ionization
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To generate voltage through magnetism what three things are needed?
- Conductor
- Magnetic field
- relative motion
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Electromagnetic Waves is generated by __ power.
AC
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Radio waves travel at what speed?
Speed of Light - 300,000,000 meters per sec
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EM waves are what type of wave form?
Transverse Waves
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Where is the stratosphere located and what effects does it have on radio waves?
Located between the troposhpere and ionosphere and has little to no effect.
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The troposphere has what effect on radio waves?
Has a great affect on RW because of weather and temperature changes
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Which layer contains four layers of electrically charged ions?
Ionosphere
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What are the two principle RF transmitting methods?
Ground and Sky waves
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What are some of the things that may affect the propagation of a radio wave?
mountains, hills, water towers, fences, other antennas, etc..
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What type of transmission is used for long range OTH communications?
Sky wave, using refraction from the ionosphere
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What are the layers of the Ionosphere during the day? Night?
- Day - D, E, F1, F2
- Night - F, E (F combine and D disappears)
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What is a skip zone?
Zone of silence between ground waves and sky waves
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What is usually the major loss of energy due to?
Spreading as the signal travels
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What some examples of natural electromagnetic interference (EMI)?
Thunderstorms, snowstorms, cosmic sources, and the sun
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What is meant by fading?
Variations in signal strength
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What is the medium for EM waves?
Nothing, EM waves travel through a vacuum
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What is ducting?
When a RW gets trapped between a tempature inversion
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What type of current is typically used when forming a radio wave?
AC - Alternating current
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When current is applied to a wire what happens?
An EM field builds around it
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The EM or radiation field is made up of what?
An electric (E) field and a magnetic (H) field
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Radio waves are expressed in terms of what?
Frequency, number of cycles per sec (hertz)
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What is wavelength?
Physical length of one complete oscillation
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What are the two primary types of polarization for radio waves?
Horizontal and vertical
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What is the basic principle of coulombs law of charges?
The amount of attracting or repelling force between two objects is determined by the distance between them and their charges
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Electric potential is measured by what?
Voltage
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What is defined as "A circuit that has current flowing in both directions"?
AC circuit
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What is true about current in a series circuit?
It remains constant throughout
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What is wattage?
The measure of power
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How much of a power difference is required to be effectively jamming?
3 dB
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What is "the variation of a property of an EM wave or signal, such as amplitude, frequency, or phase"?
Modulation
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An EM wave that can be modulated as in frequency, amplitude, or phase, to transmit speech, music, images, or other signals.
Carrier wave
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A type of radio signal in which the amplitude, or strength of a radio wave is varied in order to carry info from a transmitter to a receiver.
Amplitude Modulation
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Radio signal which freq of the radio wave is varied to carry information from transmitter to the receiver.
Frequency Modulation
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Electronic modulation in which the phase of a carrier wave is varied in order to transmit the signal.
Phase Modulation
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Modulation in which the amplitude, duration, position, or mere presence of a discrete pulse maybe so controlled as to represent the message to be communicated.
Pulse Modulation
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The range of the EM spectrum located either above or below the freq of a carrier signal.
Sidebands
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_____ is an integer multiple (exact whole #) of a fundamental frequency.
Harmonic
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Excludes undesired lower-power input signals that maybe present at or near the frequency of desired signal.
Squelch
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A combination of radio receiver and transmitter. Receives weak or low-level signal and retransmits it at a higher level.
Radio Repeater
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Digital data is represented as variations in the amplitude of a carrier wave.
ASK (Amplitude Shift Key)
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Shifts the output frequency between predetermined values to signify data.
FSK Frequency Shift Key
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Phase is changed to represent data. Two common types are Binary Quadrate.
Phase Shift Key PSK
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What three factors affect the radiation pattern of a transmitted signal?
- Antenna Configuation
- Application
- Surrounding Terrain
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What type of antenna is cheap and simple to make. Typically operates within what frequencies?
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What type of antenna provides directional capability and excellent for jamming?
Log-Periodic Antenna
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This antenna allows for wideband impedance and has a circularly polarized radiation field.
Helix Antenna
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Provides a high gain and low side lobe levels, mechanically cumbersome.
Corner Reflect Antenna
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What type is high gain reflector commonly used in TV, data links and satellite comms?
Parabolic Antenna
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Most popular omni-directional, half wave antenna.
Dipoles
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What are the four measurements radar can provide?
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Defined as "Time transmitter is sending out RF energy"
Pulse Width (PW) or Pulse Duration (PD)
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Defined as "Beginning of one pulse to the beginning of the next pulse; measured in milliseconds.
Pulse Repetition Interval (PRI)
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Number of pulses per second the Radar transmits is called what?
Pulse repetition Frequency (PRF)
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What is "the horizontal and vertical thickness of the Radar beam?
Beamwidth
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What is "The ratio of the time the transmitter operates to the time it could operate during a given transmission cycle"?
Duty Cycle
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This is where Radar has most power and where target direction usually occurs.
Main Lobe
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Directly opposite of the main lobe, significantly less power than main lobe.
Back Lobe
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Side of main lobe; 40-50 dB below main lobe.
Side Lobe
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Round trip time for RF wave to travel to and from target 1 nautical mile away.
Radar Mile
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Maximum range a Radar can detect a target due to the curvature of the Earth.
Radar Horizon
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Radar's ability to distinguish two targets at similar elevation? Similar Range? and Minimum Separation?
- Elevation Resolution
- Range Resolution
- Bearing (Azimuth) Resolution
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What are the primary components of a radar system?
- Transmitter
- Duplexer
- Receiver
- Antenna
- Display
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Create confusion & deny critical information to negate the effectiveness of EN radar is what?
Radar Jamming
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Purpose is to interfere with EN ability to pass information over link.
Communications Jamming
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What is the basic approach to jamming a digital signal?
Create bit errors 1/3 of the time.
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In Radar jamming what is the point when the jammer gets so close to the receiver that the jamming to signal ratio is less than one?
Burn-through range
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In a GSM network the two frequencies utilized for the uplink and downlink are called what and offset by what?
- Absolute Radio Frequency Channel Number
- (ARFCN)
- 45 MHz
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What are the four primary GSM bands
- GSM 850
- GSM 900
- GSM 1800
- GSM 1900
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What four databases are used by the Mobile Switching Center (MSC)?
- Home Location Registrar (HLR)
- Visitor Location Registrar (VLR)
- Equipment Identity Registrar (EIR)
- Authentication Center (AuC)
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This allows base station to communicate with the mobile device and is commonly referred to as the air interface.
Um Interface
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What are the three types of cellular access schemes used by the GSM network?
-
What two numbers are found on a cellular phone?
- International mobile equipment identity
- (IMEI)
- International Mobile Subscriber Identity
- (IMSI)
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What is the primary limitation of frequency reuse in the GSM network?
A freq can't be reused if it is shared by that of a neighboring cell.
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What part of the GSM network controls call handoffs?
Base Station System BSC
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What are the basic components of a LRCP network?
- Hand Set
- Hand Set Base Station
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What are the primary satellite communication frequencies?
- L Band (1525-1646.5 MHz) for traffic
- C, Ka, Ku, for control coms and control channels
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What does a Thuraya need in order to access the GSM network?
A roaming agreement between Thuraya and the provider
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What are the three primary Satellite communications providers? Which is total global?
- Iridium <--Global
- Inmarsat
- Thuraya
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