問題一覧
1
what is Modulation?
Changing one or more properties of a carrier signal to transmit information on it
2
FM does what?
changes the signal frequency slightly to transmit information
3
AM does what?
changes the amplitude (voltage) of a signal to transmit information
4
Two types of Modulation are?
FM & AM
5
LIMITERS are a circuit that allows…
signals below a specified input power to pass unaffected while attenuating the peaks of stronger signals that exceed this input power, It provides a constant level of signal to the FM demodulator stage, reducing the effect of signal level changes in the output
6
Resonant circuits are?
RLC circuits (resticance, inductance, capacitance), They can be made to pass or block certain frequencies
7
A RESONANT can be used to _____ (present high impedance toward) a frequency or range of frequencies, thus acting as a sort of frequency _____ to strain certain frequencies out of a mix of others.
block, filter
8
Resonant circuit serves as a _______ frequency source
stable
9
Resonance is achieved usually achieved through a ______ TANK circuit for this purpose, with the _______ and inductor directly connected together, exchanging ____ between each other.
parallel, capacitor, energy
10
Phase Locked Loops can be used to recover a _______ from a noisy communication channel, generate stable ________ at a multiple of an input _______, or distribute _____ timing pulses in digital logic designs such as microprocessors
signal, frequencies, frequency, clock
11
_______ are used to test power output from radio or transceiver, antennas output power and ________
Watt Meters, reflectance
12
When using a Watt Meter the reflectance should not be more than __% of your output
10
13
When using a Watt Meter test with the right rated Dial for _______ and ______.
Frequency, Power
14
Communication that occurs in one direction only is?
Simplex Radio
15
What allows communication in both directions, and, unlike half-duplex, allows this to happen simultaneously.
Duplex Radio
16
What separates outward and return signals. It emulates full duplex communication over a half-duplex communication link.
Time-Division Duplex
17
_______ means that the transmitter and receiver operate at different carrier frequencies.
Frequency-division duplexing
18
What are true about antennas?
converts electric currents into radio waves, and vice versa, Used for both transmitting and receiving, Higher the frequency the shorter the antenna, The best position for an antenna is centered on the roof of the truck
19
In transmission…
a radio transmitter applies an oscillating radio frequency electric current to the antenna's terminals, the antenna radiates the energy from the current as electromagnetic waves (radio waves)
20
In reception?
an antenna intercepts some of the power of an electromagnetic wave in order to produce a tiny voltage at its terminals, that is applied to a receiver to be amplified
21
_______ of an antenna is a certain frequency range at which it is most effective
bandwidth
22
One _______ of coax over other types of radio transmission line is that in an ideal coaxial cable the _________ field carrying the signal exists only in the space between the _______ conductors.
advantage, electromagnetic, inner and outer
23
Coaxial cable runs can be installed next to metal objects such as gutters without the power losses that occur in other types of transmission lines?
True
24
Coaxial cable runs cannot be installed next to metal objects such as gutters without the power losses that occur in other types of transmission lines?
False
25
Coaxial cable does not provide protection of the signal from external electromagnetic interference
False
26
Coaxial cable provides protection of the signal from external electromagnetic interference
True
27
Label COAX cable
1. plastic jacket 2. metallic shield 3. dielectric insulator 4. centre core
28
RG58
General Purpose – 50 Ohm Impedance (Audio)
29
RG59
75 Ohm Impedance (Video)
30
RG213
Heavy Duty Cable – 50 Ohm Impedance (Audio)
31
LMR400
Heavy Duty Cable – 50 Ohm Impedance (Audio)
32
Coax cable impedance ________ as frequency ________
decreases, increases
33
Impedance Is resistance to electrical flow. It includes the purely 1.______ part of a circuit, as well as 2. ______ and _______ 3.________. It is measured in 4.____
1. resistive, 2. inductive and capacitive, 3. reactance 4. ohms
34
Impedance is determined by the dielectric ______ of the inner _______ and the radii of the inner and outer ________
constant, insulator, conductors
35
A _______ cable characteristic impedance is important because the source and load impedance should be matched to ensure maximum ______ transfer and minimum __________.
controlled, power, standing wave ratio
36
Why is impedance matching a practice of designing the input impedance of an electrical load?
to maximize the power transfer or minimize reflections from the load
37
What is Standing Wave Ratio?
an efficiency measure for transmission lines, electrical cables that conduct radio frequency signals, used for purposes such as connecting radio transmitters and receivers with their antennas
38
What is SINAD?
is a power ratio, used for testing transmitters and receivers. Measures audio signal output from transmitter, compared to level of noise.
39
What is Nyquist Theorem?
Says that in order to recreate a measured signal, you must sample it at minimum twice the highest frequency of the signal
40
What does SINAD stand for?
signal to noise and distortion
41
What does CTCSS stand for?
continuous tone coded squelch system
42
a circuit that is used to reduce the annoyance of listening to other users on a shared two-way radio communications channel?
CTCSS
43
Sound that is radiated from a point source drops in level at ____ per doubling of ______
6dB, distance