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What is defined as "Most widely used system of units, both in science & everyday commerce"
International System of Units (SI)
What is a decibel (dB) used for in relation to EW?
to express the ratio of two power levels.
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
What is the formula for determining the dB difference between two power ratios?
To effectively jam a signal what must the power be?
3 dB higher or 2x as strong
Name the 3 parts of an atom and their charges?
- Electron- negative charge
- Proton - Positive charge
- Neutron - no charge
What are the 6 methods to can create voltage?
What are the two forms of energy?
Energy contained in an object due to its motion is _____ energy.
Energy contained in an object due to its position is ____ energy.
What is the process by which an atom gains or loses electrons?
What is a material that is good at allowing electricity to flow through it?
What is defined as "extremely high resistance to the flow of electricity"?
what is defined as "all matter between the extremes of conductors and insulators"?
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)
In the formula dB = (P2/P1)log x 10 what does P1 and P2 represent?
- P1 = Target / Input
- P2 = Effect / Output
What is defined as "Determined by the direction of the lines of force making up the electric field"?
This propagates in all directions
This propagates in a specific direction while minimizing propagation in other directions
Defined as "an antenna built for transmitting a certain signal is equally good at receiving that same signal"?
This is defined as "the number of waves that pass a fixed place in a given amount of time"
Time it takes for the completion, from any given point of a wave to the same point on the next wave.
The distance between repeating units of a wave, usually measured in meters?
Highest point of a wave
Crest or peak
Lowest point of a wave
Defined as "height of a sine wave measured in peak or peak-to-peak"
Defined as "movement through a medium"
What are the three layers of the Earth's atmosphere?
- Troposphere (0-16 miles)
- Stratosphere (16-30)
- Ionosphere (30-300)
Defined as "Bouncing off on substance to extend the range of a radio wave"?
Defined as "Radio wave bending as they move from one medium to another"?
This is when a radio wave "bends" around an object.
What factors affect Ionosphere refraction?
Explain the relationship between the wavelength and the frequency of the EM spectrum.
- Inversely Proportional
- High Freq = Short WL
- Low Freq = Long WL
SI is composed of what?
Base units and prefix
A negative ion has ____ than its normal amount of electrons.
a positive ion has ___ than its normal amount of electrons.
Defined as "the process by which an atom gains or loses its electrons".
To generate voltage through magnetism what three things are needed?
- Magnetic field
- relative motion
Electromagnetic Waves is generated by __ power.
Radio waves travel at what speed?
Speed of Light - 300,000,000 meters per sec
EM waves are what type of wave form?
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.
The troposphere has what effect on radio waves?
Has a great affect on RW because of weather and temperature changes
Which layer contains four layers of electrically charged ions?
What are the two principle RF transmitting methods?
Ground and Sky waves
What are some of the things that may affect the propagation of a radio wave?
mountains, hills, water towers, fences, other antennas, etc..
What type of transmission is used for long range OTH communications?
Sky wave, using refraction from the ionosphere
What are the layers of the Ionosphere during the day? Night?
- Day - D, E, F1, F2
- Night - F, E (F combine and D disappears)
What is a skip zone?
Zone of silence between ground waves and sky waves
What is usually the major loss of energy due to?
Spreading as the signal travels
What some examples of natural electromagnetic interference (EMI)?
Thunderstorms, snowstorms, cosmic sources, and the sun
What is meant by fading?
Variations in signal strength
What is the medium for EM waves?
Nothing, EM waves travel through a vacuum
What is ducting?
When a RW gets trapped between a tempature inversion
What type of current is typically used when forming a radio wave?
AC - Alternating current
When current is applied to a wire what happens?
An EM field builds around it
The EM or radiation field is made up of what?
An electric (E) field and a magnetic (H) field
Radio waves are expressed in terms of what?
Frequency, number of cycles per sec (hertz)
What is wavelength?
Physical length of one complete oscillation
What are the two primary types of polarization for radio waves?
Horizontal and vertical
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
Electric potential is measured by what?
What is defined as "A circuit that has current flowing in both directions"?
What is true about current in a series circuit?
It remains constant throughout
What is wattage?
The measure of power
How much of a power difference is required to be effectively jamming?
What are the three modes of Communication?
Simplex- signals flow in one direction
Half Duplex- flows in both direction but only one at a time
Full Duplex- flows in both direction simultaneously
What is the process of putting information on a carrier wave?
What is a electro magnetic wave that can be modulated as in frequency, amplitude, or phase?
What is Amplitude Modulation?
radio signal in which the amplitude is varied to carry information from a transmitter to a receiver
What is Frequency Modulation?
radio signal in which the frequency is varied to carry information from a transmitter to a receiver
What is Phase Modulation?
electronic modulation in which the pahseis varied to transmit information contained in the signal.
What are three major classes of digital modulation techniques?
- Phase-shift keying (PSK)
- Amplitude-shift keying (ASK)
- Frequency-shift keying (FSK
What is a form of modulation which represents digital data as variations in the amplitude of a carrier wave.
Amplitude Shift key
What are the two common examples are Phase-shift keying (PSK)
binary phase-shift keying (BPSK) which uses two phases, and quadrature phase-shift keying (QPSK) which uses four phases
What is a form of frequency modulation in which the modulating signal shifts the output frequency between predetermined values?
Frequency-shift keying (FSK)
What is a signal or wave whose frequency is an integral (whole-number) multiple of the frequency of some reference signal or wave
What is an undesired lower-power input signals that may be present at or near the frequency of the desired signal.
What is a combination of a radio receiver and a radio transmitter that receives a weak or low-level signal and retransmits it at a higher level or higher power, so that the signal can cover longer distances without degradation
What are the four major GSM frequencies that have become standard worldwide. They include GSM-900, GSM-1800, GSM-850, GSM-1900 and GSM-400.
GSM-850, GSM-900, GSM-1800, GSM-1900
What are the two network frequencies that are utilized to uplink and downlink the GSM network called?
What are they offset by?
Absloute radio frequency channel number
offset by 45 MHz
What are the four database elements of the Mobile Switching Center (MSC) are distributed to key sub-components that aid the MSC?
- Home Location Register (HLR)
- Visitor Location Register (VLR)
- Authentication Center (AuC)
- Equipment Identity Register (EIR)
WHat type of antenna is cheap and simple to make and typically operates with freqs of 12-50 MHz?
This antenna provides directional capabilities and is excellent for communications jamming.
This antenna provides high gain and low side lobes levels and is mechanically cumbersome.
Corner Reflector Antenna
Thsi antenna allows wideband impedance and has a circularly polarized radiation field.
What type of antenna is high gain reflector commonly used in TV, data links, and satellites communications?
This s the most popular omni-directional, half wave antenna
What four precise measurements can a radar provide?
In relation to radar, what is the time the transmitter sends out RF energy?
Pulse width or pulse duration
In relation to radar, what is the beginning of one pulse to the beginning to another?
Pulse repetition Interval (PRI)
In relation to radar, what is the # of pulses per second a radar transmit?
Pulse Prepetition Frequency
In relation to radar, what is Beamwidth?
Horizontal or vertical thickness of a radar beam
Whats the ratio of the time the transmitter operates to the time it could operate during a given transmission cycle?
Where does a radar have the most power and detection usually occurs?
What is located directly opposite of the main lobe and has significant less sensitivity and signal strength.
What is similar to the back lobe and adds another dimension to the radar pattern with sensitivity of 40-50 dBS?
What is the ability of a radar to display two targets flying at approximately the same range and azimuth with little altitude separation?
What is the ability of a radar to display two targets flying at approximately the same range with little angular separation
Bearing (azimuth) resolution
What is the ability of a radar to separate two targets that are close together in range and are at approximately the same azimuth and is determined by pulse width.
What are the primary components of a radar system?
What is the difference between active and passive jamming?
Active takes advantage of receiver sensitive and transmission to deny info to victim radar
Passive EM energy isn't transmitted
Explain Barrage and spot noise jamming.
Barrage sacrifices power for coverage and Spot raises the power to target frequency
What is a device that is designed to replicate similiar or better targets with electronic signatures?
What is the difference between an active decoy and a passive decoy?
- Active acts like a radar repeater which amplifies the signal and sends it back as a return,
- Passive optimizes material to ensure EM energy is returned to enemy radars
What allows the base station to communicate with the moblie devices and is commonly referred to as the air interface?
What are the three types of schemes utilized in the GSM network and explain?
- FDMA- one user gets his own ARFCN
- TDMA- user share ARFCN and is assigned a time slot
- CDMA- uses all fequencies and is assign a coding scheme
What two numbers can you find on a mobile device and what are they use for?
- IMEI-identify the mobile device
- IMSI-identify a subscriber
What is the primary limitation of frequency reuse in the GSM networks?
It cannot be reused if its shared by that of a neighboring cell
What part of the GSM network controls call handoff?
Base Station systems
What are the 2 basic components of a longe range cordless phone network?
What are the primary satellite communications frequencies?
- L Band- 1525 thru1646.5 MHz
- C Band
- Ka Band
- Ku Band
What does a Thuraya user need IOT access the GSM networks?
A roaming agreementt between Thuraya and the provider
What are the three primary Satellite communications providers and which offers global coverage?
- Iridium----Global coverage