Radio Tuner Modules

Modulation, defined as a process that changes waves from one form to another is done by the use of a module or a modulator.  The process causes the signals to expand, repressing them so that there is an accurate transmittal of the signal.  The carrier signal in tuners is a low frequency signal and is transmitted using a high frequency “sinusoid waveform”, or “sine wave”.  This wave can alter three key components so as to modulate a signal in relation with the low frequency signal.

A sine wave’s amplitude is the height of the oscillation or the “volume”. The phase is the measure of one wave to another or the “timing” of the wave.  The number of times the oscillations occurs in a specified amount of time is the frequency or the “pitch” and the higher the frequencies, the more waves are produced in a given time.

A low frequency message signal can be transmitted by amplitude modulation (AM) or frequency modulation (FM) radio waves. In AM, the strength of the transmitted signal is varied in relation to the information that is being transmitted. The signal is produced by expelling the power at the carrier frequency and in to adjoining bands of frequencies called sidebands. Each sideband is equal in bandwidth to that of the modulating signals and are exact images of each other. A sideband’s bandwidth is the difference between the upper and lower points the radio wave can be heard in a signal spectrum. Bandwidths are usually measured in hertz which is defined as the number of cycles per second. The signal spectrum is a range of waves at various frequencies that emit different length receptors. Each radio station transmits those waves on an assigned frequency or channel.

A radio tuner uses an antenna to add them all together and picks out one channel at a time which results in the various stations we can listen to.
One type of signal is called double sideband amplitude modulation (DSB-AM) in which two sidebands surround a carrier but much of the power is wasted in the carrier making it less effective. The carrier can be removed or suppressed to make it more efficient resulting in double-sideband suppressed-carrier that produces a reduced-carrier transmission. This is three times more effective in terms of power compared to the DSB-AM. A reduced-carrier transmission reduces the level of the carrier wave which allows the two sidebands to have higher power levels.

Even more effective is frequency modulation radio waves in which the frequency of modulation is changed. This type of modulation uses very high frequencies (VHF) to transmit signals. These high frequencies are boosted prior to transmission and then reduced by the same amount in the receiver. This is known as pre-emphasis and de-emphasis respectively and concentrates the signals around the VHF so they can be effectively transmitted.

In both AM and FM radio waves, a radio has to be tuned into each frequency  which then produces a small number of listening stations using a large amount of spectrum.