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Pipeline - Mod 5 > 1a - Radio Theory > Flashcards

1a - Radio Theory Flashcards

1
Q

Enables us to send information to a receiver to another location;
Also called a radio transmitter.

A

Transmitters

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2
Q

Radio transmitters transform energy from a(n) _____ power source into a(n) __________ at a radio frequency.

A

DC ; AC

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3
Q

What makes up a transmitter?

A

Power Supply
Electronic Oscillator
Audio Amplifier
Modulator/Mixer
RF Amplifier
Control Circuits
Antenna Tuner/Coupler
Antenna

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4
Q

Provides power for all the electronic circuits: the oscillator, the modulator, the power amplifier; the RF control, and, in some cases, the antenna tuner/coupler.

A

Power supply

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5
Q

Converts DC current into a continuous alternating waveform at a given amplitude and frequency. The frequency is kept accurate and stable by a Phased Locked Loop (PLL).

A

Oscillator / VCO

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6
Q

Used to keep the oscillator frequency stable and accurate by means of an error voltage.

A

Phased Lock Loop (PLL)

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7
Q

The key to PLL operation is its ability to detect the phase difference between a ______ and the oscillator _____. The amount of ______ produced is based on this phase difference.

A

Reference frequency ; Output frequency; Error voltage

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8
Q

The ____ is used to automatically maintain a stable and accurate output frequency from the oscillator.

A

Error voltage

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9
Q

Four elements of a PLL

A

Phase comparator/detector
VCO
Frequency divider
Reference frequency

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10
Q

Compares two signals, detects their difference in phase, then produces an error voltage based on that phase difference.

A

Phase comparator / detector

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11
Q

Generates the RF signal normally considered the output of the loop. Frequency output (carrier) is kept stable by the error voltage from the phase comparator/detector.

A

VCO

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12
Q

Divides the output path from the VCO to route a sample of the frequency to the phase comparator/detector.

A

Frequency Divider

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13
Q

Set by the user. Tells the VCO which frequency to produce.

A

Reference Frequency

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14
Q

Increases the strength of audio from the microphone to a level strong enough to mix with the carrier frequency in the modulator.

A

Audio amplifier

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15
Q

Takes an audio signal and superimposes (overlays) a representation of that signal onto a carrier frequency.

A

Modulator/mixer

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16
Q

A ______ is a pure wave of constant frequency produced by the VCO.

A

Carrier wave

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17
Q

The process of superimposing an input signal onto a carrier wave is called _____.

A

Modulation

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18
Q

Used by transmitters to amplify the RF signal before it is sent to the antenna to be transmitted. Can also amplify received signals or radio pulses.

A

RF amplifier

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19
Q

______ allows the desired frequency band to be amplified while blocking undesired frequencies.

A

Tunable amplifiers

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20
Q

Also known as Transmit Gain Control (TGC);
Compares the power of the output signal to the radio’s power limit.

A

RF Control

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21
Q

____ and _____ are variable inductor and capacitor circuits used to match the antenna’s impedance and the feedline’s impedance to ensure a maximum transfer of power.

A

Antenna couplers ; antenna tuners

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22
Q

Antenna couplers are placed at the _____. They change the ____ of the antenna to match the impedance of the ______.

A

antenna feed point; impedance; feedline

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23
Q

Antenna tuners are placed at the ______. Some antenna tuners may be built into ____.

A

output of the transmitter; the radio

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24
Q

_____ applies power to the transmit circuits and releases the oscillator frequency to the modulator for modulation.

A

“Keying” the radio

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25
Q

Pushing the ___ button “keys” the radio.

A

PTT

26
Q

The ____ produces the carrier frequency.

A

oscillator

27
Q

The ____ is a pure wave that is constant in both amplitude and frequency.

A

Carrier frequency

28
Q

The level of amplification applied to the audio signal is determined by the audio signal’s ____.

A

strength

29
Q

____ is the electronic component in the modulator that combines the modulating signal (intelligence) with the carrier (oscillator) frequency. This process is called _____.

A

The mixer (Field Effect Transistor); modulation

30
Q

The three signals modulation produces at the output of the modulator:

A

The oscillator frequency (carrier)
The upper sideband (USB) frequency
the Lower sideband frequency (LSB)

31
Q

The ____ will increase the signal to the required power necessary to reach the intended receiver.

A

RF amplifier

32
Q

Other names for the RF control circuit

A

Transmit Gain Control (TGC)
Automatic Power Control (APC)
Automatic Load Control (ALC)

33
Q

The purpose of the _____ is to maintain the transmitter output power (wattage) at a constant level.

A

RF Control

34
Q

____ are variable inductor and capacitor circuits used to match impedance of the source (radio/transmission line) and the load (antenna) for the frequency being transmitted.

A

Antenna coupler/tuners

35
Q

A coupler is placed at the ____ to the antenna whereas a tuner is placed at the ____ of the transmitter.

A

input ; output

36
Q

The ____ cleans up the signal before the next stage in the transmission path…This prevents interference with other frequencies within the radio as well as preventing erroneous signals radiating out of the antenna.

A

filter

37
Q

The purpose of a _____ is to recover the intelligence sent from the distant end.

A

receiver

38
Q

What makes up a receiver?

A

Power supply
Antenna
Tuner
RF amplifier
Oscillator
Mixer
Detector (demodulator)
Automatic gain control (AGC)
Audio amplifier

39
Q

Where “pre-selection” happens. The ___ (pre-selector) only selects the AC for the selected receive frequency and blocks all others.

A

tuner

40
Q

The ___ separates the intelligence (voice/data) from the IF.

A

detector (demodulator)

41
Q

The ____ is a closed-loop feedback regulating circuit for an amplifier or chain of amplifiers.

A

Automatic Gain Control (AGC) circuit

42
Q

The purpose of the AGC circuit is to keep the amplifier output level at _____ even when the input signal varies in ____.

A

the proper value ; amplitude

43
Q

The ____ takes the output signal from the detector, amplifies it to an audible level, and then applies it to a speaker.

A

audio amplifier

44
Q

Receiver signal flow?

A

Power supply (cannot function without power)
Antenna -> Tuner -> RF amplifier -> Mixer (AGC and Oscillator go into Mixer; AGC from Detector) -> Detector -> Audio amplifier -> Speaker

45
Q

The ____ takes the signal from the tuner and increases its strength to a sufficient level for the heterodyning process in the mixer.

A

RF amplifier

46
Q

The ____ is non-discriminate, so a tuner is needed to select the desired frequency and reject all others.

A

Antenna

47
Q

The ____ heterodynes the received RF signal with the frequency from the oscillator. As a result, four frequencies (equal in amplitude) will be at the output of the mixer: ___, ___, ___, ____

A

mixer;
oscillator, received rf, USB, and LSB frequencies

48
Q

The ____ “detects” and extracts intelligence from the IF and sends it to the audio speaker.

A

detector

49
Q

The ____ keeps the intelligence output at a preset level, even when the power level of the received signal changes.

A

AGC voltage

50
Q

The ___ selects only the desired frequencies and reject all others. This narrows the bandwidth which minimizes errors before the next stage in the receive path.

A

filters

51
Q

A ____ contains both a transmitter and a receiver in one package.

A

transceiver

52
Q

The purpose of transceivers is to enable the ____ and ____ of intelligence over the air ways (wireless).

A

transmission ; reception

53
Q

The three categories of transceivers?

A

Simplex
Half-duplex
Full-duplex

54
Q

____ transceivers use one frequency, which is used for both transmit and receive. You cannot do both at the same time.

A

Simplex

55
Q

_____ transceivers uses two frequencies– one for transmit and a different one for receive. When not “keyed”, the transceiver will remain in the receive function

A

Half-duplex

56
Q

____ transceivers can transmit and receive at the same time.

A

Full-duplex

57
Q

What does the T/R Relay component do?

A

Switches from antenna to transmit and v/v;
Also switches the oscillator from the oscillator receive frequency to the oscillator transmit frequency.

58
Q

The power supply provides ___ current power in transmit and ___ current power in receive.

A

high ; low

59
Q

The ____ is the percentage of time to transmit and the percentage of time to receive.

A

duty cycle

60
Q

Most transceivers operating in the simplex or half-duplex mode will have a duty cycle of ___ or ___

A

20%/80% ; 10%/90%

61
Q

Transmit time is always ____ than receive time in duty cycles.

A

shorter

62
Q

____ uses software to replace the transmitter and receiver components that have typically been implemented in hardware.

A

Software Definted Radio (SDR)

Pipeline - Mod 5 (2 decks)

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