1. The interchanging of the frequencies of carrier channels to accomplish specific purposes, such as to prevent feedback and oscillation, to reduce crosstalk, and to correct for a high frequency-response slope in the transmission line.
Note: Frequency frogging is accomplished by having modulators, which are integrated into specially designed repeaters, translate a low-frequency group to a high-frequency group, and vice… (Read More →)

A frequency band deliberately left vacant between two channels to provide a margin of safety against mutual interference.

[The] repeated switching of frequencies during radio transmission according to a specified algorithm, to minimize unauthorized interception or jamming of telecommunications. [NIS] [INFOSEC-99]
Note: The overall bandwidth required for frequency hopping is much wider than that required to transmit the same information using only one carrier frequency.

One frequency used for one hour regardless of the number of transmitters over which it is simultaneously broadcast by a station during that hour. [47CFR]

See frequency stability.

The condition in which a frequency-correcting feedback loop maintains control of an oscillator within the limits of one cycle.
Note: Frequency lock does not imply phase lock, but phase lock does imply frequency lock.

Modulation in which the instantaneous frequency of a sine wave carrier is caused to depart from the center frequency by an amount proportional to the instantaneous value of the modulating signal.
Note 1: In FM, the carrier frequency is called the center frequency.
Note 2: FM is a form of angle modulation.
Note 3: In optical communications, even if the… (Read More →)

Synonym FOT.

See FOT.
In the transmission of radio waves via ionospheric reflection, the highest effective, i.e., working, frequency that is predicted to be usable for a specified path and time for 90% of the days of the month.
Note 1: The FOT is normally just below the value of the maximum usable frequency (MUF). In the prediction of usable frequencies, the… (Read More →)

The difference between the frequency of a source and a reference frequency.