Transmitters and Receivers Glossary

AF Amplifier.  See Audio-Frequency Amplifier.

AGC.  See Automatic Gain Control.

AM Demodulator.  An AM demodulator is used in an AM receiver to shift the carrier frequency of an amplitude modulated signal to a lower frequency.

AM Modulator.  An AM modulator is used to provide amplitude modulation in a transmitter.

AM Receiver.  An AM receiver is used to receive an amplitude modulate signal, to demodulate and amplify it.

AM Transmitter.  An AM transmitter transmits and amplitude modulated (AM) signal.

Audio-Frequency Amplifier (AF Amplifier).  The audio-frequency amplifier (AF amplifier) stage develops sufficient AF power to operate the loudspeaker, handpiece or other output device.

Audio Receiver.  An audio receiver is a receiver designed to demodulate and amplify a sound signal

Automatic Gain Control (AGC).  A receiver therefore includes automatic gain control (AGC) to maintain the signal at the input to the detector at a constant value despite fluctuations in the signal strength at the antenna.

Balanced Modulator.  In a balanced modulator, a signal is modulated using two carriers that are 180 degrees out of phase.

Bluetooth Receiver.  A Bluetooth receiver receives signals from a Bluetooth transmitter, demodulates and decodes them and passes the received information to a host device for processing.

Bluetooth Transmitter.  A Bluetooth transmitter encodes, modulates and transmits data from its host device to one or more Bluetooth receivers.

Co-Channel Interference.  Co-channel interference occurs when another signal is received in the same channel as the wanted signal and therefore cannot be eliminated by the receiver itself.

Cross Modulation.  Cross modulation is caused by non-linearity in the RF amplifier or the mixer and results in the transfer of the amplitude modulation of a strong, unwanted carrier onto the wanted carrier.

Crystal Oscillator.  Receivers operating at one or more fixed frequencies can use a crystal oscillator with frequency changes accomplished by switching between crystals.

De-Emphasis Network.  The purpose of the limiter is to remove any amplitude variations that exist in the signal before it reaches the detector to avoid any distortion during the demodulation process

Demodulator.  A demodulator is used in a receiver to shift the carrier frequency of a received signal to a lower frequency.

Denon Receivers.  Denon receivers offer many features, including Dolby surround sound, digital audio decoding and a number of filtering options.

Detector.  The output of the IF amplifier is applied to the detector, which recovers the information from the modulated signal.

Digital Audio Receiver.  A digital audio receiver demodulates and decodes a digital bitstream containing compressed digital audio signals

Digital Audio Transmitter.  A digital audio transmitter modulates and transmits a digital bitstream containing compressed digital audio signals

Digital Satellite Receiver.  A digital satellite receiver is designed to receive a digital signal from a satellite.

Digital Television Receiver (Digital TV Receiver).  A digital television receiver demodulates and amplifies a received digital television signal, that is then passed to a digital decoder.

Digital Television Set-Top Box (Digital TV STB).  A digital television set-top box (digital TV STB) is usually an integrated receiver decoder (IRD).

Digital Television Transmitter.  A digital television transmitter is a form of television transmitter that emits a digitally encode television signal.

Digital TV Receiver.  See Digital Television Receiver.

Digital TV STB.  See Digital Television Set-Top Box.

Direct TV Receivers (DirectTV Receivers).  Direct TV (DirectTV) provides digitial satellite television services.

DirectTV Receivers.  See Direct TV Receivers.

Earthmate GPS Receiver.  The Earthmate GPS receiver is a WAAS (wide area augmentation system) enabled GPS system.

External Tone Squelch.  In external-tone squelch, an inaudible 150-Hz tone is added to the audio signal before it is modulated onto the carrier in the transmitter.

FM Demodulator.  An FM demodulator is part of an FM receiver, and is used to shift the carrier frequency of a frequency modulated signal to a lower frequency.

FM Direct Method.  See Frequency Modulation - Direct Method.

FM Indirect Method.  See Frequency Modulation - Indirect Method.

FM Modulator.  An FM modulator is used to provide frequency modulation in a transmitter.

FM Receiver.  An FM receiver is designed to receive frequency-modulated signals.

FM Transmitter.  An FM transmitter transmits a frequency modulated (FM) signal.

Frequency Modulation - Direct Method (FM Direct Method).  In the direct method of frequency modulation (FM), a circuit whose reactance can be controlled by the amplitude of the modulating signal is connected in parallel with a variable-frequency LO.

Frequency Modulation - Indirect Method (FM Indirect Method).  Improved frequency stability can be provided by the indirect method of frequency modulation (FM), which is able to use a crystal LO.

Frequency Stability.  The stability of the transmitter’s local oscillator frequency is critical, particularly in AM systems such as SSB where the receiver is required to re-insert the carrier.

Frequency Synthesis.  A frequency synthesiser can generate any carrier frequency within the frequency band of the radio from a single accurate high-stability crystal oscillator.

Frequency Synthesiser - Direct Method.  In the direct frequency synthesiser method the required carrier is obtained through a process of frequency multiplication, mixing and filtering.

Frequency Synthesiser - Indirect Method.  Most modern equipments use the indirect method of frequency synthesis, in which the required output frequency is derived from a voltage-controlled oscillator whose accuracy is maintained by phase-locking the oscillator to a standard frequency.

Garmin GPS Receiver.  The Garmin GPS receiver stable includes systems for aviation, marine, vehicle and handheld navigation. Applications include flying, boating, hiking and driving.

GPS Receiver.  A GPS receiver is designed to receive signals from GPS satellites, and to process these signals to provide geolocation information.

HDTV Receiver.  An HDTV receiver is a receiver that is designed to receive and demodulate high-definition television signals.

HDTV Set-Top Box (HDTV STB).  An HDTV Set-Top Box (HDTV STB) is an integrated receiver decoder (IRD) designed to receive and decode HDTV signals.

HDTV STB.  See HDTV Set-Top Box.

HDTV Transmitter (High Definition Television Transmitter).  An HDTV transmitter (High Definition Television Transmitter) is a television transmitter that emits a digitally encoded, HDTV signal.

High Definition Television Transmitter.  See HDTV Transmitter.

IF Amplifier (Intermediate Frequency Amplifier).  The IF amplifier (intermediate-frequency amplifier) provides most of the gain and the selectivity of the superheterodyne receiver.

IF Breakthrough.  If a signal at the intermediate frequency (IF) is allowed to reach the mixer, it will also appear within the pass band of the IF amplifier and interfere with the wanted signal. This effect is known as IF breakthrough.

Image Channel Interference.  When the superheterodyne receiver is tuned to the wanted frequency there is always another frequency (known as the image frequency or image signal) that, when mixed with the local oscillator, will also produce the IF.

Independent Sideband Receiver.  See ISB Receiver.

Independent Sideband Transmitter.  See ISB Transmitter.

Intermediate Frequency Amplifier.  See IF Amplifier.

Intermodulation.  Within the receiver there are a number of components which must be operated linearly to avoid producing harmonics that may combine with unwanted signals to produce various difference frequency components (known as intermodulation products).

Internal Tone Squelch.  Internal-tone squelch places the onus for squelch on the receiver only. In the receiver, the LO frequency is FM-modulated by an 85-Hz tone before it is mixed with the incoming signal.

ISB Receiver (Independent Sideband Receiver).  An ISB receiver (Independent Sideband receiver) is able to receive two separate signals, one on the lower sideband, the other on the upper sideband, of a common carrier.

ISB Transmitter (Independent Sideband Transmitter).  An ISB transmitter (independent sideband transmitter) is a form of DSB transmitter (double sideband transmitter) in which each sideband carries an independent baseband signal.

Limiter.  The purpose of the limiter is to remove any amplitude variations that exist in the signal before it reaches the detector to avoid any distortion during the demodulation process.

LNA.  See Low-Noise Amplifier.

Local Oscillator.  When the receiver is required to tune across a frequency band, the local oscillator (LO) must be capable of tuning to be offset by the IF away any frequency in the band.

Low-Noise Amplifier (LNA).  The term low-noise amplifier (LNA) is most commonly applied to the first stage of amplification in a satellite receiver.

Lower Sideband Receiver.  See LSB Receiver.

Lower Sideband Transmitter.  See LSB Transmitter.

Lowrance GPS Receivers.  The Lowrance family of GPS receivers is aimed at marine and outdoor applications.

LSB Receiver (Lower Sideband Receiver).  An LSB receiver (lower sideband receiver) is a form of SSB receiver (single sideband receiver).

LSB Transmitter (Lower Sideband Transmitter).  An LSB transmitter (lower sideband transmitter) is a form of SSB transmitter (single sideband transmitter) that transmits only on the lower sideband.

Magellan GPS Receiver.  There are a number of different types of Magellan GPS receiver, including handheld and vehicle navigation systems.

Mixer.  In the mixer stage of a receiver, the wanted signal frequency is mixed with the output of the local oscillator (LO) to produce the difference frequency as the intermediate frequency (IF).

Modulator.  A modulator is used in a transmitter to frequency-shift a signal.

Navman GPS Receiver.  Navman produce marine, vehicle and OEM GPS receivers for navigation.

Noise Squelch.  Noise squelch uses the presence or absence of noise at the input of the receiver to disable the audio amplifier.

Power Amp.  See Power Amplifier.

Power Amplifier (Power Amp).  A power amplifier is one that is designed to provide a high output current to drive a low-impedance load.

Pre-Emphasis Network.  The pre-emphasis network is the first half of a system consisting of a pre-emphasis network in the transmitter and a de-emphasis network in the receiver.

Pre-Selection.  The pre-selection section is responsible for avoiding image channel interference, IF breakthrough, co-channel interference, intermodulation products, and cross-modulation products.

Radio-Frequency Amplifier (RF Amplifier).  Typically the radio-frequency amplifier (RF amplifier) provides gain of the order of 10–30 dB (about 10 to 1,000 times amplification).

Radio Frequency Stage (RF Stage).  The incoming signal is very weak and must be amplified by the RF stage before being passed to the mixer. The RF stage must also prevent certain troublesome frequencies. The RF stage therefore consists of RF amplification and pre-selection sections.

Radio Receiver.  At the end of the radio channel is the radio receiver.

Radio Transmitter.  A radio transmitter modulates an input signal using a suitable carrier frequency, which translates the signal to an allocated part of the electromagnetic spectrum.

Receiver.  At the end of the communications channel is the receiver, which must be able to select the desired signal from all the signals present at the antenna, amplify and demodulate, and present it to the source in the appropriate format.

Receiver Design.  Receiver design is concerned with matching equipment to specific application requirements.

Receiver Noise Figure.  The noise figure or noise factor (F) of a radio receiver is a measure of the degree to which the receiver degrades the input SNR.

Receiver Selectivity.  The selectivity of the receiver is its ability to receive the wanted signal and reject unwanted signals in adjacent channels.

Receiver Sensitivity.  The sensitivity of a radio receiver is its ability to amplify weak received signals to produce a useable output.

RF Amplifier.  See Radio-Frequency Amplifier.

RF Stage.  See Radio Frequency Stage.

Rockwell/Collins GPS Receiver.  Rockwell Collins produces the GPS 4000A GPS receiver.

Satellite Receiver.  A satellite receiver is designed to receive, amplify and demodulate signals transmitted by a satellite

Single Sideband Receiver.  See SSB Receiver.

Single Sideband Transmitter.  See SSB Transmitter.

Sky Satellite Television Receiver.  Sky offers digital television services via satellite.

Socket Communications GPS Receiver (Socketcom GPS Receiver).  The Socket Communications GPS Receiver Socketcom GPS Receiver) is a Bluetooth enabled GPS receiver.

Socketcom GPS Receiver.  See Socket Communications GPS Receiver.

Solid State Amplifier (SSA).  A solid-state transmitter is one that employs transistors for all amplification.

Solid State Power Amplifier (SSPA).  A solid state power amplifier (SSPA) is a transmitter power amplifier that uses semiconductor devices (transistors) for all amplification.

Sony Receivers.  Sony audio receivers provide a wide range of features, including surrond sound with Dolby Prologic, optical and electrical interfaces and video switching.

Squelch.  Squelch is used to disable the audio output of a receiver unless a signal is present.

SSA.  See Solid State Amplifier.

SSB Receiver (Single Sideband Receiver).  An SSB receiver (single sideband receiver) receives a signal modulated on one sideband of a carrier.

SSB Transmitter (Single Sideband Transmitter).  An SSB transmitter single sideband transmitter) transmits only on one sideband.

SSPA.  See Solid State Power Amplifier.

Superheterodyne Receiver.  The basis of a superheterodyne radio receiver is the translation of the wanted signal frequency into a constant frequency known as the intermediate frequency.

Television Receiver (TV Receiver).  A television receiver is the demodulator and amplifier that is used prior to decoding of analog or digital television signals.

Television Transmitter (TV Transmitter).  A television transmitter (TV transmitter) transmits a television signal.

Transistor Amplifier.  A transistor amplifier is one whose electronic circuits are based on transistors, rather than alternative technologies such as values of travelling wave tubes.

Transmitter.  At the transmitter the information signal is used to modulate a suitable carrier frequency, which translates the signal to an allocated part of the electromagnetic spectrum.

Transmitter Design.  Transmitter design is concerned with matching equipment to specific application requirements.

Travelling Wave Tube Amplifier (TWTA).  In a travelling wave tube amplifier (TWTA), the input signal is used to modulate the velocity of electrons near the source of an electron beam.

TV Receiver.  See Television Receiver.

TV Transmitter.  See Television Transmitter.

TWTA.  See Travelling Wave Tube Amplifier.

Upper Sideband Receiver.  See USB Receiver.

Upper Sideband Transmitter.  See USB Transmitter.

USB Receiver (Upper Sideband Receiver).  A USB receiver (upper sideband receiver) is a form of SSB receiver (single sideband receiver) that receives signals modulated on the upper sideband of a carrier.

USB Transmitter (Upper Sideband Transmitter).  A USB transmitter (upper sideband transmitter) is a form of SSB transmitter (single sideband transmitter) that transmits only on the upper sideband.

Valve Amplifier.  A valve amplifier is one in which a valve (or vaccuum tube) is used to provide amplification.

Yamaha Receivers.  The Yamaha range of receivers includes video receivers, audio-visual receivers, mini systems, intelligent remote control and DSP integrated amplifiers and processors.

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