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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 .
Have Quick (also HAVEQUICK, short HQ) is an ECM-resistant frequency-hopping system used to protect military aeronautical mobile (OR) radio traffic. Since the end of World War II , U.S. and Allied military aircraft have used AM radios in the NATO harmonised 225–400 MHz UHF band (part of NATO B band [ 1 ] ) for short range air-to-air and ground ...
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]
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 allows several users to share the same frequency channel by dividing the signal into different time slots. [1] The users transmit in rapid succession, one after the other, each using its own time slot. This allows multiple stations to share the same transmission medium (e.g. radio frequency channel) while using only a part of its channel ...
Frequency-hopping spread spectrum (FHSS) applies a special scheme for channel release MSK and GMSK are particular cases of continuous phase modulation. Indeed, MSK is a particular case of the sub-family of CPM known as continuous-phase frequency-shift keying (CPFSK) which is defined by a rectangular frequency pulse (i.e. a linearly increasing ...
Frequency settling time is the time it takes the PLL to hop to another frequency. Frequency hopping is used in GSM, and still more in modern systems. In CDMA, frequency hopping achieves better performance than phase coding. Fine frequency resolution is the capability of a PLL to generate closely spaced frequencies.
The mode also employs multiple frequency-shift keying, but at 44 tones. One of the tones is a synchronization tone, leaving 43 tones to carry data (one tone per character in the character set, which includes alphanumerics and some punctuation). The symbol rate is 21.53 baud; the actual data rate as encoded for transmit is 14.4 characters per second