A prediction of the maximum usable frequency (MUF), the optimum traffic frequency, and the lowest usable frequency (LUF) for transmission between two specific locations or geographical areas during various times throughout a 24-hour period.
Note: The prediction is usually indicated by means of a graph for each frequency plotted as a function of time. [From Weik '89]

A continuous range or spectrum of frequencies that extends from one limiting frequency to another.
Note 1: The frequency range for given equipment specifies the frequencies at which the equipment is operable. For example, filters pass or stop certain bands of frequencies. The frequency range for propagation indicates the frequencies at which electromagnetic wave propagation in certain modes or paths… (Read More →)

See insertion-loss-vs. -frequency characteristic.

A plot of the gain or attenuation of a device, such as an amplifier or a filter, as a function of frequency.
Note: A flat curve indicates a uniform gain or attenuation over the range of frequencies for which the curve is flat. Most amplifiers have a flat frequency response over a certain band, above and below which the gain… (Read More →)

Conducting a search for signals over a band or range of frequencies by means of a manually or automatically tuned receiver.
Note: The tuning rate, i.e., the frequency change rate, may be fixed or variable, or it may be performed mechanically at low speed or electronically at high speed. Frequency scanning may be used to enable a radar to transmit… (Read More →)

The assignment to or use of the same radio frequency by two or more stations that are separated geographically or that use the frequency at different times.
Note 1: Frequency sharing reduces the potential for mutual interference where the assignment of different frequencies to each user is not practical or possible.
Note 2: In a communications net, frequency sharing does… (Read More →)

1. Any change in frequency.
2. Any change in the frequency of a radio transmitter or oscillator.
Note: In the radio regime, frequency shift is also called rf shift.
3. See frequency-shift telegraphy.
4. In facsimile, a frequency modulation system where one frequency represents picture black and another frequency represents picture white. Frequencies between these two limits may represent shades… (Read More →)

See frequency standard.

See electromagnetic spectrum.

The situation that occurs when many stations transmit simultaneously using frequencies that are close together, i.e., with insufficient width of frequency guard bands or channel spacing.
Note: Frequency spectrum congestion causes (a) difficulty in discrimination by tuning, (b) overlap of (i) a sideband and an adjacent carrier, or (ii) upper and lower sidebands, respectively, of adjacent carriers, and (c) interference… (Read More →)