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= Modulation =
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Modulation is the altering of a carrier signal to add infomration. This is done
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in everything from raido, to Ethernet.
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== Bandwidth ==
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Bandwidth is the amount of frequencies that a signal occupies. For example, the
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Human voice can make frequencies from 300Hz to 3000Hz, therefore having a
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bandwidth of 3000 - 300 = 2700Hz.
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== Types of Modulation ==
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=== CW ===
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Bandwidth: 150hz
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Continuous Wave of CW is a type of signal where the pulsing of the signal
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encoded information, instead of modifying the carrier signal. An example of
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this is Morse code. Due to how concentrated the signal is, CW is used for
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extreme ranges.
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=== AM ===
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Bandwidth: 6khz (voice); 10khz (broadcast)
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Amplitude Modulation of AM is a form of modulation where the amplitude of the
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signal is changed to encode information. The signal as a result will take up
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space both above and below the carrier, called Upper Side Band (USB) and Lower
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Side Band (LSB).
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2021-11-12 19:30:01 +00:00
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AM has a Peak Envelope Power. This is determined by the max power of the
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transmitter, and the Mic gain.
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2021-11-12 19:15:01 +00:00
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=== SSB ===
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Bandwidth: 2-3khz (voice); 500-3000hz (digital)
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Single Side Band (SSB) Is when an AM signal is encoded by only modulating one
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part of the signal, and leaving the other unchanged. This allows for less
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bandwidth use for the same information.
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Due to SSB concentrating the same amount of power for the signal into a
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narrower portion of the signal, it is often used for long distance VHF and UHF
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(see [[frequency_range]]).
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Standards have formed around SSB, and wether to use USB or LSB on different
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frequencies. If < 10Mhz, LSB. Else if >= 10Mhz, USB.
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2021-11-12 19:30:01 +00:00
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SSB has a Peak Envelope Power. This is determined by the max power of the
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transmitter, and the Mic gain.
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2021-11-12 19:15:01 +00:00
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=== FM/PM ===
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Bandwidth: 10-15khz (voice); 150khz (broadcast)
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Frequency Modulation (FM) and Phase Modulation (PM) are two similar types of
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modulation where the signal is encoded by changing either the frequency of the
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signal, or the phase of the signal.
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2021-11-12 19:30:01 +00:00
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Because FM/PM does not change in amplitude, the power output is fixed.
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Therefore, the PEP is fixed as well.
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2022-01-16 02:15:01 +00:00
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== QAM ==
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Quadrature Amplitude Modulation. See [[QAM]]
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2021-11-12 20:15:01 +00:00
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=== Digital ===
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There are several different types of digital signals, all determined by their
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corresponding protocol.
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2021-11-12 19:30:01 +00:00
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== Overmodulation ==
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Over modulation or splattering is when the signal is to heavily modulated,
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making it use to much bandwidth. This is generally negative, and can often be
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fixed by speaking softly, changing mic gain, or moving away from the mic.
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2021-11-12 19:30:01 +00:00
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The sound it makes to the reciever is a 'breaking up' sound, where distortion
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occours on voice peaks.
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