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75 Cards in this Set
- Front
- Back
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Spectrum Analyzer
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Magnitude (power) on y -axis
Frequency (Hz) on x- axis |
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OSI Model
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7 - Application
6 - Presentation 5 - Session 4 - Transport 3 - Network 2 - Data Link 1 - Physical |
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Physical Layer Technology?
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OFDM, Ethernet Hubs. FHSS
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Data Link Layer Technology
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MAC addresses, 802.11, 802.3
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Network
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IP, Routers, packet filters
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Transport
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TCP, UDP
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Session
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RCP, Some parts of TCP
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Presentation
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Encryption Protocols, SSL, HTTPS
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Application
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Most Firewalls, FTP, POP3, HTTP
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Hook batteries in parallel
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Increases Current
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Hook batteries in Series
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Increases Voltage
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AC
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Electric Current in which direction of flow reverses at frequent regular intervals
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DC
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Electric Current that flows in one direction
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Amp
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Unit of electrical current going through a wire
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Watt
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One Amp under the pressure of one volt
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Volt
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Unit of force that causes electrons to flow through a wire
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Power = Watts (W) =
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V(volts) X A(Amps)
1000W = 1kW |
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Series Wiring
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Positive Terminal to Negative Terminal
Increases Voltage |
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Parallel Wiring
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Positive to Postitive
Increases Amps |
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Loads in Series are Bad!
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Because they cause a additive voltage drop. If one light burns out, the other receives no power
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Loads in Parallel are Good!
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Voltage remains constant. Each load can be controlled individually.
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Frequency
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# of cycles per second. Frequency is measured in Hz, one complete cycle.
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Freq Ranges
HF VHF |
HF: 3- 30 MHz (Shortwave)
VHF : 30 - 300 MHz (Radio, FM Broadcasting) |
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Freq Ranges
UHF |
UHF : 300 MHz - 3 GHz (Cordless Telephones, GPS)
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Freq Ranges
SHF EHF |
SHF : 3 - 30 GHz (WiFi, Satellites)
EHF : 30 - 300 GHz (Microwave) |
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GPRS
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General Packet Radio Service
Works with GSM to enable mobile devices to send Packets. Users get assigned a Uplink/Downlink Freq. |
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Rescue 21 has:
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* portable radio towers
* fully housed communications shelters * satellite backup communications * remotely located watchstander equipment * remotely located backroom operating equipment |
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What is the definition of Gain
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Signal going into the device is smaller then the device going out
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What is a amplifier
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A device which causes Gain
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Describe an impedance matching circuit.
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A circuit capable of changing the impedance with different values for incoming and outgoing impedance.
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What is the L-Band
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1-2 GHz , GPS Band!
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What’s the relation between dB and change of signal?
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+3 dB is 2 times bigger, +10 dB is 10 times bigger
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What is a dB
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A Comparative Logarithmic Power Measurement
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what is dBm
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It is a absolute power measurement in milliwatts
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what is dBi
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It is a measurement against a isotropic radiator
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what is dBd
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Measurement against a dipole antenna,
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0 dBd = ? dBi
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2.14
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How many bels in a decibel
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1/10 of a bel
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RF signals experience ? decay as they travel
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logarithmic. They lose power exponentially
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How do you convert mW to a dBm measurement?
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10 X log10(Power in mW)
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Noise Floor
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The level of Background Noise
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SNR
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Power of your RF Signal relative to the power level of the noise floor
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RSSI
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Arbitrary level of received signal strength
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Link Budget
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A accounting of all components of power, gain, loss, receiver sensitivity, and fade margin
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Fade Margin
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The amount by which a received signal level may be reduced without causing system performance to fall below a specified threshold value.
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Multipath
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propagation phenomenon that results in radio signals' reaching the receiving antenna by two or more paths
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Fresnel Zone
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LOS Zone that is blocked by the bulge of the earth
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Loss : Reflection
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Signal bounces off of a surface and changes direction
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Loss : Refraction
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Occurs when a RF Signal changes speed and is bent while moving between different densities
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Loss : Diffraction
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Change in direction or intensity of a wave as it passes by the edge of a obstacle
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Loss : Scattering
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RF Signal strikes a uneven surface and spreads so the resulting signals are less significant then the original signal
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Loss : Absorption
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Material absorbs the signal
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Impedance mismatching
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Impedance bridging is unsuitable for RF connections because it causes power to be reflected back to the source from the boundary between the high impedance and the low impedance. The reflection creates a standing wave, which leads to further power waste. In these systems, impedance matching is essential.
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What is impedance
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??
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VSWR
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A Measurement of mismatched impedance in a RF System, usually a ratio.
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Return Loss
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Backward reflection of the signal toward the transmitter
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Free Space Path Loss
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Weakening of RF Signal due to broadening of the wave front.
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sideband
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a band of frequencies higher than or lower than the carrier frequency, containing power as a result of the modulation process.
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How fast do radio waves travel?
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The speed is 300,000,000 meters per second
or 186,000 miles per second or The Speed of Light. |
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A Transmission Lines has what two things?
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Antenna Portion and a Ground Portion.
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Every antenna has how many poles?
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Antenna and the ground plane
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How do you calculate the length of the antenna
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234 / Freq in MHz = # of ft to get a 1/4 wavelength
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Polarization of the Antenna
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Horizontal sends waves Vertical, Vertical sends waves Horizontal. Think of a bow and a arrow
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Factors determining propagation of radio signal
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Frequency, Polarization of Antenna, Height of Antenna
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What is more dangerous to humans, the volts or the Amps?
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The Amps is what will hurt you
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What is a vector?
What is a scalar? |
Vector: Magnitude + Direction
Scalar: Magnitude |
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Series Circuit
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One or more resistors (loads) connected to a voltage source with one path for Electron Flow
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Parallel Circuit
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Two or more different paths for the current to flow
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VSAT
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Very Small Aperture Terminal
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KU Band
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Satellite Band
Downlink: 11.7-12.7 GHz Uplink: 14 - 14.5 GHz |
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HF Field Expedient Antenna
Ground: |
Vertical Wire
Sloping Wire (vary angle ) Antenna is 1/4 or freq wavelength |
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HF Field Expedient Antenna
Sky: |
1/2 Wave Length Horizontal Dipole
Ins-(-)--1/4---Cobrahead---1/4-(+)--Ins. |
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Ohm
Volt Amp Watts(Power) |
A measurement of Resistance
Pressure Current/Electron Flow Volts X Amps |
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OHM's Law
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It takes one volt of electrical pressure to push one amp of electrical current through a resistance of one ohm
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Volts = ?
Current = ? |
Current X Resistance
Voltage / Resistance |
