Automatic Frequency Control. System to maintain frequency of operation of transmitting or receiving equipment.

Automatic Gain Control. System to maintain constant signal level during varying conditions.

Above Ground Level. Refers to mounting center height of antenna above ground, for FCC licensing requirements.

Above Mean Sea Level. Refers to height of terrain above sea level (0 feet). Either + (elevation), or - (depression).

Microwave frequency measuring device.

Those components which have gain, or direct current flow.

Device providing gain from input to output.

Ratio of output signal level to input signal level, usually in dB.

Absolute or relative level of a quantity.

Transmission of intelligence by varying the level of the transmitting medium.

Microwave equipment using AM modulation.

Inability of a device to maintain a constant gain relationship for all levels of input.

A form of transmitting information characterized by continuously variable quantities, as opposed to digital transmission, which is characterized by discrete bits of information in numerical steps. An analog signal is responsive to changes in light, sound , heat and pressure.

Process of converting analog signals to digital representation. DAC represents the reverse translation.

Deviations from normal signal propagation conditions.

Device used to radiate or receive radio transmissions.

Theoretical point source radiating a spherical power envelope.

Antenna utilizing a reflector shaped as a paraboloid to both concentrate the radiated signal into a beam and provide considerable gain. Beamwidth varies inversely and gain directly with the size of the antenna and with frequency.

Percentage of radiated signal transmitted or received in a given direction related to beamwidth.

Percentage of theoretical gain actually realized.

The effectiveness of a directional antenna expressed as the ratio of input power of the directional to input power of an isotropic radiator to provide the same field strength in the desired direction. Sometimes related to a dipole antenna.

Parabolic Antenna Gain:
G=20logF +20log D
+ 10 log h - 50
where:
F = Frequency MHz
D = Diameter feet
G = Gain dB
h = efficiency (» 0.54)

Attenuation of the transmitted signal due to water vapor and gasses in the air.

Bending of the transmitted signal due to varying atmospheric density.

Device to insert known attenuation in the transmission path.

The carrier between 5 MHz and 8 MHz containing audio (or voice) information inside of a video carrier.

Direction of movement or measurement in the horizontal plan relative to the earth's surface. Usually related to degrees from true north.

Adjustment fixture on a parabolic antenna to both support the dish and to move it horizontally.

Transmission line having both conductors equal impedance to ground. in FM microwave systems Zo = 120 ohms.

Frequency spectrum occupied by a given number of discrete frequencies.

The range of frequencies that can handled by a device.

Ratio of two devices having differing bandwidths. Not necessarily in the same frequency spectrum.

The rate of data transmission based on the number of signal elements or symbols transmitted per second. Today most digital signals are characterized in bits per second.

A single digital unit of information.

The fraction of a sequence of message bits that are in error. A bit error rate of 10-6 means that there is an average of one error per million bits.

The speed of a digital transmission, measured in bits per second.

An ordinary television signal consists of 30 separate still pictures or frames sent every second. They occur so rapidly, the human eye blurs them together to form an illusion of moving pictures. This is the basis for television and motion picture systems. The blanking interval is that portion of the television signal which occurs after one picture frame is sent and before the next one is transmitted. During this period of time special data signals can be sent which will not be picked up on an ordinary television receiver.

An on-channel repeater that is normally an active amplifier without frequency conversion.

A heart-shaped curve or antenna pattern.

Basic frequency of transmission. Modulated frequency.

Number and type of signals carried by particular equipment of systems.

Ratio of input carrier level to input noise level, or output carrier to output noise level, existing in a given system.
C/N = Pt + Gt + Gr +- Nr
where:
Pt = transmitted power dBm
Gt = transmit antenna gain dB
Gr = receive antenna gain dB
A = path attenuation dB
Nr = receiver noise = FKTB
F = noise figure
T = temperature (Kelvin)
K = Boltzmans constant
B = bandwidth

An enclosure, usually cylindrical, designed to respond to a particular range of frequencies determined by the dimension.

A series of microwave resonant cavities designed to pass a certain frequency or band of frequencies.

Code division multiple access. Refers to a multiple-access scheme where stations use spread-spectrum modulations and orthogonal codes to avoid interfering with one another.

The abbreviation for the Conference European des Postes et Telecommunications standards (Committee for European & Postal Telecommunications Services).

Antenna center line above ground. See AGL.

A band of frequencies containing the carrier frequency and all its associated modulation.

devices designed to pass only one channel. Sometimes known as a Pass Band Filter (PBF).

Nominal impedance value of a transmission line or network.
Zo = (L/C) 1/2

An integrated circuit.

A microwave waveguide connector flange with choke groove designed to minimize mismatch.

Three port ferro-magnetic directional microwave device designed to pass power in only one direction. Used to combine or separate different frequencies. cascade circulators are referred to as a Circulator Chain.

Differing from Plane Polarization in that E Field components exist in a 360° plane perpendicular to the direction of propagation.

Transmission line having an inner conductor surrounded by insulation and an outer braid or sheath serving as the other conductor.

Reception of an undesired carrier on the same frequency assignment.

A subcarrier that is added to the main video signal to convey the color information. In NTSC systems, the color subcarrier is centered on a frequency of 3.579545 MHz, referenced to the main video carrier.

Any organization which operates communications circuits used by other people. Common carriers include the telephone companies as well as the owners of the communications satellites, RCA, Comsat, Direct Net Telecommunications, AT&T and others. Common carriers are required to file fixed tariffs for specific services.

Gain control through detection of one or more composite video signals at baseband. Used instead of a CW pilot frequency.

A common intermodulation distortion present in multichannel AM system such as CATV and MMDS. Characterized by horizontal streaking in a television picture.

Sinusoidal waveform of constant frequency and amplitude.

Selection of frequencies in high spectrum density areas to preclude interference of other users on the same band.

Companion microwave connector flange to the Choke Flange.

A waveguide device that provides directional samples of energy present in the main guide.

Undesired modulation on a carrier from other carriers in a wideband device due to third order distortions.

Undesired coupling between signals in isolated or separate transmission paths.

Antennas or waveguide carrying signals in opposite planes (90°) apart.

Direct broadcast satellite. Refers to service that uses satellites to broadcast multiple channels of television programming directly to home mounted small-dish antennas.

The offset angle of an antenna from the axis of its polar mount as measured in the meridian plane between the equatorial plane and the antenna main beam.

A digital-to-analog convertor.

The time it takes for a signal to go from the sending station through the satellite to the receiving station. This transmission delay for single hop satellite connection is very close on one-quarter of a second.

The operation on a carrier wave to recover the wave with which the carrier was originally modulated.

A dielectric ceramic material used in filters and oscillators.

Measure of the linearity of the gain of a video amplifier from black level to white level in the video signal.

Measure of the phase delay of the video amplifier to the color subcarrier over the gain range of the amplifier.

The bending of electromagnetic waves around the edge or surface of an obstruction.

Conversion of information into bits of data for transmission through wire, fiber optic cable, satellite, or over air techniques. Method allows simultaneous transmission of voice, data or video.

A technique of reducing digital bit rate through the elimination of signal redundancy.

Semiconductor device having a single PN junction, and the property of construction in only one direction.

A detector circuit using diodes.

Specialized microwave diode used in microwave oscillators.

Specialized microwave diode used in microwave oscillators.

Special diode for microwave and UHF multiplier applications.

Special diode with an abrupt breakdown characteristic, used in multipliers.

Microwave filtering device used to mix outputs or separate inputs. Mostly replaced by circulators in newer equipment.

A device to split an incident transmission to two separate paths, and to absorb reflections from the sampled (coupled) line.

Demodulation circuit used to recover the modulation from frequency modulated signals. Responds to FREQUENCY variations.

Parabolic antenna.

Lack of fidelity in the reproduced signal.

The use of either different receive locations or antenna heights (Space Diversity), or different frequency bands (Frequency Diversity) on the same transmission path to obtain greater reliability of operation.

A device that heterodyne converts an input frequency to a specified output frequency.

Amplifier to feed the final power or conversion stage.

Delivery point to a customer on a common carrier microwave system.

Either antennas or waveguide carrying signals 90° apart in phase.

The ability of the atmosphere to form channels or ducts which can trap microwave signals causing severe fading of the received levels.

Effective Radiated Power relative to an isotropic radiator.

Effective Radiated Power. Antenna power input increased by the antenna gain. Sometimes known as EIRP, Effective Isotropic Radiated Power.

A satellite receiving system.

Apparent radius of the earth due to radio refraction in the atmosphere. Usually given as "K" factor.

Microwave antenna movement in the vertical plane.

A corrugated semiflexable elliptical shaped waveguide transmission line.

An analog-to-digital convertor.

Providing varying attenuation or gain in a network or device, to compensate for distortion in previous stages.

Frequency division multiple access. Refers to the use of multiple carriers within the same transponder where each uplink has been assigned frequency slot and bandwidth. This is usually employed in conjunction with Frequency Modulation.

Frequency Modulation. A modulation method whereby the baseband signal varies the frequency of the carrier wave.

That point at which the input signal power is just strong enough to enable the receiver demodulator circuitry to successfully detect and recover a good quality television picture from the incoming video carrier.

Frequency Modulated Oscillator.

Frequency Shift Keying.

Loss of received signal level due to various phenomena.

Amount of received signal level fade that can be tolerated before arriving at a minimum desired level into the receiver.

Final waveguide device radiating or receiving at the antenna. Sometimes known as the feed horn.

Ferro-magnetic device to attenuate microwave signals.

Amplifier controlling DC current to the ferrite attenuator to attenuate microwave signals.

Ferro-magnetic device permitting incident signals to pass while attenuating reflections.

That area nearest the radiating antenna where the beam is undergoing formation.
Near Field Radius (Parabolic):
R = 2D2 /l
where: D = dish diameter (ft)
l = wavelength (ft)

Distance from the center feed to the center of the dish.

The area toward which the primary reflector directs and concentrates the signal received.

Adds unique codes to the digital signal at the source so errors can be detected and corrected at the receiver.

Attenuation of the atmosphere to radio transmission.
LS = 96.6 + 20log F +20logD
where: F = frequency (GHz)
D = Distance (miles)

That portion of the microwave beam that would, if reflected by an obstruction, arrive either in phase (reinforcement) or out of phase (cancellation) at the receiver. Fresnel Radii are known as zones. Odd zones reinforce and even zones cancel. Fresnel zones are derived through geometric relationships: the effects diminish with increasing zone numbers (greater distance from the center of the beam, thus lower power).1st Fresnel Zone Radius:
F, = 72.1 [(d, dz)/(fD)]1/2
nth Fresnel Zone Radius:Fn = F, (n) 1/2
where:
F1 = 1st Fresnel Radius (ft)
Fn = nth Fresnel Radius (ft)
dn = distance to reflection point (miles)
D = distance of the path (miles)= d, +d2
f= freqency (GHz)

A process to eliminate frequency interference between microwave systems and satellites. In the U.S. this activity relies upon a computerized service utilizing an extensive database to analyze potential microwave interference problems that arise between organizations using the same microwave band.

Able to change channels rapidly without component changes.

The frequency range specified by a governing agency, within which a radio is authorized to operate.

The amplitude vs. frequency response of a network.

The variation in a carrier's frequency that occurs over a time period and/or temperature range.

The ratio of forward antenna gain to reverse antenna gain.

Ability to transmit and receive signals at the same time.

High Definition Television.

Multiple of a base carrier frequency.

Filter to eliminate harmonic transmission.

Electronic control center, generally located at the transmit site of the CATV system.

Cycles-per-second.

Up or Down conversion in frequency, of a carrier by beating it against a second carrier and using the sum or difference.

Circuit using techniques of IC's and discrete components.

Instructional Television Fixed Services.

International Telecommunications Union.

The AC resistance of a device or component, containing reactance.

The selection of input device impedance to match the output impedance of the driving device for maximum power transfer.

The characteristic of an FM modulated system that results in a Signal to Noise Ratio improvement when the input is above the threshold level. The threshold level is nominally 10dB C/N.
FMI = 10 log [3 (Fd/Fv)2 ] dB

Composite video signal spectrum containing aural subcarrier at 4.5 MHz and at a standard transmission level of 1/10 video peak to peak.

Loss to the through signal level due to inserting a device in the line. Related to VSWR.
AI = 10 log (T) 2 + 1

4 1/2 " pipe mount to attach antenna to tower or other mounting surface.

Resulting frequency from the first down conversion in a super - heterodyne receiving system.

Second and Third order distortion components produced by mixing of discrete signals in an amplifying system.

Also known as Thermal and White noise. Produced by random motion of electrons in a conducting medium.
Nt = 4RKTB (for a resistor)
where:
R = Resistance (ohms)
K = Boltzmans Constant
1.38 X 10 -13 joules
T = Temperature (Kevin)
oK = oC - 273

Microwave frequency aperture to allow signal coupling from a cavity to waveguide or other cavities (such as in a filter).

Integrated Services Digital Network) A CCITT standard for integrated transmission of voice, video and data. Bandwidths include: Basic Rate Interface - BR (144 Kbps - 2 B & 1 D channel) and Primary Rate - PRI (1.544 and 2.048 Mbps).

Coupling attenuation between signals in a desired bath to an undesired path in the same device. Alternately, coupling attenuation between separate circuits.

Device to pass microwave power in one direction, but presenting a termination to transmission in the opposite direction. Similar to a circulator with one port terminated.

Same values when measured along all directions.

Kilobits per second. Refers to transmission speed of 1,000 bits per second.

Effective Earth radius.

Microwave thermionic device used as an amplifier or oscillator. Operates by electron beam transit time & cavity interaction.

Diffraction of the microwave beam over a pointed edge of infinite length.