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Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly changing the carrier frequency among many frequencies occupying a large spectral band. The changes are controlled by a code known to both transmitter and receiver .
Other applications include antenna testing, frequency stability and frequency accuracy checking. Usually a WSPR station contains a computer and a transceiver, but it is also possible to build very simple beacon transmitters with little effort. For example a simple WSPR beacon can be built using the Si 570, [5] or Si 5351. [6]
Frequency (subcarrier) interleaving increases resistance to frequency-selective channel conditions such as fading. For example, when a part of the channel bandwidth fades, frequency interleaving ensures that the bit errors that would result from those subcarriers in the faded part of the bandwidth are spread out in the bit-stream rather than ...
Frequency agility is the ability of a radar system to quickly shift its operating frequency to account for atmospheric effects, jamming, mutual interference with friendly sources, or to make it more difficult to locate the radar broadcaster through radio direction finding.
Practical synchronous digital systems radiate electromagnetic energy on a number of narrow bands spread on the clock frequency and its harmonics, resulting in a frequency spectrum that, at certain frequencies, can exceed the regulatory limits for electromagnetic interference (e.g. those of the FCC in the United States, JEITA in Japan and the ...
It usually performs 1600 hops per second, with adaptive frequency-hopping (AFH) enabled. [25] Bluetooth Low Energy uses 2 MHz spacing, which accommodates 40 channels. [26] Originally, Gaussian frequency-shift keying (GFSK) modulation was the only modulation scheme available.
An RF sweep relates to a receiver which changes its frequency of operation continuously from a minimum frequency to a maximum (or from maximum to minimum). Usually the sweep is performed at a fixed, controllable rate, for example 5 MHz/sec. Some systems use frequency hopping, switching from one
M17 uses Frequency-Division Multiple Access (FDMA) technology in which different communication streams are separated by frequency and run concurrently. It utilizes 4,800 symbols per second, 4-level frequency-shift keying (4FSK) with a root Nyquist filter applied to the bitstream. Radio channels are 9 kHz wide, with channel spacing of 12.5 kHz.