2021-11-12 18:15:01 +00:00
|
|
|
= Modulation =
|
|
|
|
|
|
|
|
|
|
Modulation is the altering of a carrier signal to add infomration. This is done
|
|
|
|
|
in everything from raido, to Ethernet.
|
|
|
|
|
|
|
|
|
|
== Bandwidth ==
|
|
|
|
|
|
|
|
|
|
Bandwidth is the amount of frequencies that a signal occupies. For example, the
|
|
|
|
|
Human voice can make frequencies from 300Hz to 3000Hz, therefore having a
|
2021-11-12 19:15:01 +00:00
|
|
|
bandwidth of 3000 - 300 = 2700Hz.
|
|
|
|
|
|
|
|
|
|
== Types of Modulation ==
|
|
|
|
|
|
|
|
|
|
=== CW ===
|
|
|
|
|
|
|
|
|
|
Bandwidth: 150hz
|
|
|
|
|
|
|
|
|
|
Continuous Wave of CW is a type of signal where the pulsing of the signal
|
|
|
|
|
encoded information, instead of modifying the carrier signal. An example of
|
|
|
|
|
this is Morse code. Due to how concentrated the signal is, CW is used for
|
|
|
|
|
extreme ranges.
|
|
|
|
|
|
|
|
|
|
=== AM ===
|
|
|
|
|
|
|
|
|
|
Bandwidth: 6khz (voice); 10khz (broadcast)
|
|
|
|
|
|
|
|
|
|
Amplitude Modulation of AM is a form of modulation where the amplitude of the
|
|
|
|
|
signal is changed to encode information. The signal as a result will take up
|
|
|
|
|
space both above and below the carrier, called Upper Side Band (USB) and Lower
|
|
|
|
|
Side Band (LSB).
|
|
|
|
|
|
2021-11-12 19:30:01 +00:00
|
|
|
AM has a Peak Envelope Power. This is determined by the max power of the
|
|
|
|
|
transmitter, and the Mic gain.
|
|
|
|
|
|
2021-11-12 19:15:01 +00:00
|
|
|
=== SSB ===
|
|
|
|
|
|
|
|
|
|
Bandwidth: 2-3khz (voice); 500-3000hz (digital)
|
|
|
|
|
|
|
|
|
|
Single Side Band (SSB) Is when an AM signal is encoded by only modulating one
|
|
|
|
|
part of the signal, and leaving the other unchanged. This allows for less
|
|
|
|
|
bandwidth use for the same information.
|
|
|
|
|
|
|
|
|
|
Due to SSB concentrating the same amount of power for the signal into a
|
|
|
|
|
narrower portion of the signal, it is often used for long distance VHF and UHF
|
|
|
|
|
(see [[frequency_range]]).
|
|
|
|
|
|
|
|
|
|
Standards have formed around SSB, and wether to use USB or LSB on different
|
|
|
|
|
frequencies. If < 10Mhz, LSB. Else if >= 10Mhz, USB.
|
|
|
|
|
|
2021-11-12 19:30:01 +00:00
|
|
|
SSB has a Peak Envelope Power. This is determined by the max power of the
|
|
|
|
|
transmitter, and the Mic gain.
|
|
|
|
|
|
2021-11-12 19:15:01 +00:00
|
|
|
=== FM/PM ===
|
|
|
|
|
|
|
|
|
|
Bandwidth: 10-15khz (voice); 150khz (broadcast)
|
|
|
|
|
|
|
|
|
|
Frequency Modulation (FM) and Phase Modulation (PM) are two similar types of
|
|
|
|
|
modulation where the signal is encoded by changing either the frequency of the
|
|
|
|
|
signal, or the phase of the signal.
|
|
|
|
|
|
2021-11-12 19:30:01 +00:00
|
|
|
Because FM/PM does not change in amplitude, the power output is fixed.
|
|
|
|
|
Therefore, the PEP is fixed as well.
|
|
|
|
|
|
2021-11-12 20:15:01 +00:00
|
|
|
=== Digital ===
|
|
|
|
|
|
|
|
|
|
There are several different types of digital signals, all determined by their
|
|
|
|
|
corresponding protocol.
|
|
|
|
|
|
2021-11-12 19:30:01 +00:00
|
|
|
== Overmodulation ==
|
|
|
|
|
|
|
|
|
|
Over modulation or splattering is when the signal is to heavily modulated,
|
|
|
|
|
making it use to much bandwidth. This is generally negative, and can often be
|
|
|
|
|
fixed by speaking softly, changing mic gain, or moving away from the mic.
|
2021-11-12 19:15:01 +00:00
|
|
|
|
2021-11-12 19:30:01 +00:00
|
|
|
The sound it makes to the reciever is a 'breaking up' sound, where distortion
|
|
|
|
|
occours on voice peaks.
|
2021-11-12 20:15:01 +00:00
|
|
|
|
|
|
|
|
|
