1812 WOBC -Follow On Classs
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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 is "the variation of a property of an EM wave or signal, such as amplitude, frequency, or phase"?
An EM wave that can be modulated as in frequency, amplitude, or phase, to transmit speech, music, images, or other signals.
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.
Radio signal which freq of the radio wave is varied to carry information from transmitter to the receiver.
Electronic modulation in which the phase of a carrier wave is varied in order to transmit the signal.
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.
The range of the EM spectrum located either above or below the freq of a carrier signal.
_____ is an integer multiple (exact whole #) of a fundamental frequency.
Excludes undesired lower-power input signals that maybe present at or near the frequency of desired signal.
A combination of radio receiver and transmitter. Receives weak or low-level signal and retransmits it at a higher level.
Digital data is represented as variations in the amplitude of a carrier wave.
ASK (Amplitude Shift Key)
Shifts the output frequency between predetermined values to signify data.
FSK Frequency Shift Key
Phase is changed to represent data. Two common types are Binary Quadrate.
Phase Shift Key PSK
What three factors affect the radiation pattern of a transmitted signal?
- Antenna Configuation
- Surrounding Terrain
What type of antenna is cheap and simple to make. Typically operates within what frequencies?
What type of antenna provides directional capability and excellent for jamming?
This antenna allows for wideband impedance and has a circularly polarized radiation field.
Provides a high gain and low side lobe levels, mechanically cumbersome.
Corner Reflect Antenna
What type is high gain reflector commonly used in TV, data links and satellite comms?
Most popular omni-directional, half wave antenna.
What are the four measurements radar can provide?
Defined as "Time transmitter is sending out RF energy"
Pulse Width (PW) or Pulse Duration (PD)
Defined as "Beginning of one pulse to the beginning of the next pulse; measured in milliseconds.
Pulse Repetition Interval (PRI)
Number of pulses per second the Radar transmits is called what?
Pulse repetition Frequency (PRF)
What is "the horizontal and vertical thickness of the Radar beam?
What is "The ratio of the time the transmitter operates to the time it could operate during a given transmission cycle"?
This is where Radar has most power and where target direction usually occurs.
Directly opposite of the main lobe, significantly less power than main lobe.
Side of main lobe; 40-50 dB below main lobe.
Round trip time for RF wave to travel to and from target 1 nautical mile away.
Maximum range a Radar can detect a target due to the curvature of the Earth.
Radar's ability to distinguish two targets at similar elevation? Similar Range? and Minimum Separation?
- Elevation Resolution
- Range Resolution
- Bearing (Azimuth) Resolution
What are the primary components of a radar system?
Create confusion & deny critical information to negate the effectiveness of EN radar is what?
Purpose is to interfere with EN ability to pass information over link.
What is the basic approach to jamming a digital signal?
Create bit errors 1/3 of the time.
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?
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
- 45 MHz
What are the four primary GSM bands
- GSM 850
- GSM 900
- GSM 1800
- GSM 1900
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)
This allows base station to communicate with the mobile device and is commonly referred to as the air interface.
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
- International Mobile Subscriber Identity
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.
What part of the GSM network controls call handoffs?
Base Station System BSC
What are the basic components of a LRCP network?
- Hand Set
- Hand Set Base Station
What are the primary satellite communication frequencies?
- L Band (1525-1646.5 MHz) for traffic
- C, Ka, Ku, for control coms and control channels
What does a Thuraya need in order to access the GSM network?
A roaming agreement between Thuraya and the provider
What are the three primary Satellite communications providers? Which is total global?
- Iridium <--Global
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