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Characteristics
Radio Frequency signals consist of the following:• Polarity• Wavelength• Frequency• Amplitude• Phase
These characteristics are defined by the laws of physics.
Characteristics -- Polarity
Polarity is the position and direction of an electric field as it is referenced to the surface of the earth. There are two positions:• Vertical polarization: This is when the field is perpendicular
to the earth.• Horizontal polarization: This is when the field is parallel to
the earth.
Characteristics -- Wavelength
The wave length is the distance between two peaks (or two troughs) on two back to back waves.
Characteristics -- Frequency
Frequency refers to how fast a wave will travel, and how many waves are generated over a 1 second period of time.
The higher the frequency, the lower the distance. The lower the frequency, the higher the distance. For example: 750 KHz wave will travel 1,312 feet.2.45 GHz wave will travel 4.8 inches5.775 GHz wave will travel 2 inches.252 GHz (satellite) wave will travel at .05 inches 1 hertz (Hz) = 1 cycle per second1 kilohertz (KHz) = 1,000 cycles per second1 megahertz (MHz) = 1 million cycles per second1 gigahertz (GHz) = 1 billion cycles per second
Characteristics -- Amplitude
This is the reference to the strength or power of the signal. When looked through an oscilloscope, the amplitude is referenced by positive crests and negative troughs of the sine wave. The bigger, the stronger.
Not amp... ...Amplitude
Characteristics--Phase
• Is the relationship between two waves of the same frequency.
• A wave is divided into 360 "degrees". • These degrees are also counted as "starting times"
o So, if one wave starts at "0" degrees, then another starts at 90 degrees, then that 2nd wave is considered to be 90 degrees out of phase.
• If a signal is 180 degrees out of phase from another, then the two waves would cancel each other out. The signal strength becomes null.
• Lastly, depending on the phase of separation, the signal is either strengthened or weakened.
RF Behaviors
Wave Propagation
Types of Propagation
Line-of-Sight
Sky Wave
Ground Wave
Reflection
Absorption
Scattering
Refraction & Diffraction
Multipath
SummaryThe Basics of Radio Frequency:
• Electromagnetic waves and how they are generated • The relationship between wavelength, frequency, and the
speed of light• Signal Strength and the various ways in which a signal can
either attenuate or amplify• The importance of the relationship between two or more
signals• How a signal moves by bending, bouncing, or absorbing in
some manner
For the Exam...Understand - Wavelength, Frequency, Amplitude, and Phase. Also know the definitions and how they can effect wireless LANRemember RF propagation Behaviors - Reflection, Refraction etc... what are the differences and mediums associated with themAttenuation Causes - On wire or air, absorbtion, free space path loss, and multipath downfall all cause attenuationFree Space Loss - Electromagnetic waves attenuate in a measureable manner as they travel away from the transmitter, despite no obstructionsFour Multipath Results - May cause downfade, upfade, nulling and data corruptionResults of Intersymbol Interference and Delay Spread - The time differential between a primary signal and a reflected signal may cause data corruption and affect output through retransmissionActive and Passive Gain - RF amplifiers are active (active gain) devices, whereas antennas are passive (passive gain) devices
...basically, understand the review questions REALLY well since all the Quiz questions are taken from there
anyways.
Right Brother Ericson?
Attenuation
Diffraction
Delay Spread
AmplitudeWaveLengthFrequency