MOD10 Flashcards
Amplitude
—The magnitude of change in the height of the radio wave. This is the amount of power
introduced to the signal.
Frequency
The number of cycles completed by a periodic quantity in a unit of time. The number
of cycles per second (1/Frequency)
Wavelength
It is the distance between
consecutive corresponding points of the same phase on the wave, such as two adjacent crests or
troughs.
Frequency and Wavelength have an _____________ relationship
Inverse
Wavelength =
= the speed of light divided by
the frequency of the signal.
Wavelength is measured in __________
meters
study of radio wave propagration
how radio waves move in free space and over the surface of
the earth.
Ground Waves
Ground waves travel at or near the earth’s surface. At lower frequencies (below
2MHz) in the mediumwave and longwave bands
Line of Sight
This refers to radio waves that travel in a straight line from the transmitting
antenna to the receiving antenna.
the only
method of propagation possible at frequencies above 30MHz.
Line of Sight
can communicate with satellites and spacecraft billions of miles from earth.
Ground Stations
“skip” or skywave propogation
radio waves
directed at an angle into the sky can return to Earth beyond the horizon
The Ionosphere
the region of the
atmosphere that extends from about 30-250 miles above the earth’s surface.
The Ionosphere contains what layers
D, E & F layers
The F Layer
breaks up into two layers (F1 and F2) during the daylight hours.
The D Layer
is ionized very strongly during the day (noon is the strongest) and tends to restrict the
lower HF frequencies from refracting efficiently
The E Layer
has weaker ionization, and the lower frequencies
work well and the higher frequencies do not function as well.
AM broadcast band
530kHz to 1700kHz
Heterodyning
combines
two or more frequencies (i.e., the RF carrier wave & the user data/intelligence wave) across a
nonlinear device to produce new frequencies.
the sum frequency is also known as…
USB
Upper Side Band
the difference frequency is also known as…
LSB
Lower Side Band
Single Side Band
a variant of AM that uses transmitter power and bandwidth more efficiently
by suppressing the carrier and eliminating one of the sidebands.
