1A - HF Transceiver Equipments Flashcards
The HF band extends from _________.
3MHz - 30MHz
We characterize an AM radio wave as having an _____.
amplitude, a frequency, and a wavelength.
The magnitude of change in the height of the radio wave. This is the amount of power introduced to the signal.
Amplitude
The number of cycles completed by a periodic quantity in a unit of time. The number of cycles per second (1/Frequency).
Frequency
The distance over which the wave’s shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests or
troughs.
Wavelength
Frequency and wavelength have an ____ relationship.
inverse
The symbol for wavelength is Greek letter ____.Wavelength = ____________. Wavelength is measured in ____.
lambda (λ)
the speed of light divided by the frequency of the signal
meters
How radio waves move in free space and over the surface of
the earth is called:
Radio wave propagation
____ travel at or near the earth’s surface.
Ground waves
This refers to radio waves that travel in a straight line from the transmitting
antenna to the receiving antenna.
Line of Sight (LOS)
____ is the only method of propagation possible at frequencies above 30MHz.
LOS
On the surface of the earth, LOS propagation is limited by the visual horizon to about _____.
64 km (40 miles)
The ____ layers are all responsible for HF long haul communications, but the _ layer allows communications to take place beyond an estimated 1,500 miles.
D, E, and F
F
____ combines two or more frequencies (i.e., the RF carrier wave & the user data/intelligence wave) across a
nonlinear device to produce new frequencies.
Heterodyning
The sum frequency is also known as the ___.
upper sideband (USB)
The difference frequency is also known as the ___.
lower sideband (LSB)
The modulated carrier wave is also known as the ___.
composite signal
Another aspect of AM is that ____ are transmitted even though they contain the same information.
both the sidebands
The carrier consumes ___ of the total power produced while the sidebands take up ___.
two thirds
the other third
These sidebands occupy from ____ (first 300Hz is filtered out because it is considered noise) to a maximum of ___ on each side of the center frequency for a maximum total bandwidth of ___.
300Hz
3,000Hz
6000Hz (6kHz)
Single Side Band is a variant of AM that uses transmitter power and bandwidth more efficiently by ____.
suppressing the carrier and eliminating one of the sidebands.
_____ refers to decreasing the bandwidth of each channel in a radio system. This creates more channels in the overall radio spectrum (in our case HF).
Spectrum conservation
Two aspects of power efficiency:
- Available power is concentrated in the one utilized sideband.
- Power output is only developed when carrier is modulated with intelligence (data or voice).
The bandwidth of a SSB receiver is ___ the bandwidth of an AM receiver to receive the same signal.
less than half
