Page 50 - DCAP311_DCAP607_WIRELESS_NETWORKS

Wireless Networks

Notes

Did u know? The TRX900 internal IFB audio option adds the ability to receive IFB
(confidence) audio directly on the bodypack via the built-in 2.4 GHz receiver. To monitor
audio an EA100 or Stereo Adapter is required.

3.2 Understanding RF Signals

A frequency of electromagnetic radiation in the range at which radio signals are transmitted,
ranging from approximately 3 kilohertz to 300 gigahertz. Many astronomical bodies, such
as pulsars, quasars, and possibly black holes, emit radio frequency radiation is called radio
frequency.

3.2.1 RF Signal Attributes

All RF waves have characteristics that vary to define the wave. Some of these properties can be
modified to modulate information onto the wave. These properties are wavelength, frequency,
amplitude, and phase.

z z Wavelength: The wavelength of an RF wave is calculated as the distance between two
adjacent identical points on the wave. For example, Figure 2.3 shows a standard sine wave.
Point A and Point B mark two identical points on the wave, and the distance between them
is defined as the wavelength. The wavelength is frequently measured as the distance from
one crest of the wave to the next.

z z Frequency: Frequency refers to the number of wave cycles that occur in a given window
of time. Usually measured in second intervals, a frequency of 1 kilohertz (KHz) would
represent 1000 cycles of the wave in 1 second. To remember this, just keep in mind that a
wave cycles frequently and just how frequently it cycles determines its frequency.
z z Amplitude: You might wonder that the volume of sound waves is dependent on the
frequency, since lower-frequency waves are heard at a greater distance; however, there
is actually another characteristic of waves that impacts the volume. Remember, at greater
distances, shorter-wavelength waves are more difficult to detect as the waveform spreads
ever wider (though this may be more a factor of the antenna used than of the waveform
itself). The characteristic that defines the volume is known as amplitude. In sound wave
engineering, an increase in amplitude is equivalent to an increase in volume; hence, an
amplifier adds to the volume, or makes the sound louder. While the frequency affects the
distance a sound wave can travel, the amplitude affects the ability to detect (hear) the
sound wave at that distance. RF waves are similar.

z z Phase: Unlike wavelength, frequency, and amplitude, phase is not a characteristic of a single
RF wave but is instead a comparison between two RF waves. If two copies of the same
RF wave arrive at a receiving antenna at the same time, their phase state will impact how
the composite wave is able to be used. When the waves are in phase, they strengthen each
other, and when the waves are out of phase, they sometimes strengthen and sometimes
cancel each other. In specific out-of-phase cases, they only cancel each other. Phase is
measured in degrees, though real-world analysis usually benefits only from the knowledge
of whether the waves are in phase or out of phase. Two waves that are completely out of
phase would be 180 degrees out of phase, while two waves that are completely in phase
would be 0 degrees out of phase. Figure 2.6 shows a main wave signal, another in-phase
signal, and an out-of-phase signal.
!

Caution When troubleshooting wireless networks, the phase of duplicate RF signals is
mostly an implication of reflection or scattering in an area that may cause dead zones due
to the out-of-phase signals.

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