Mobile Satellite Service (MSS) is a type of mobile telephone service that depends on portable terrestrial satellites rather than fixed terrestrial satellites that are also known as cell phone towers. Portable terrestrial satellites are similar to cell phone towers, but can be mounted on moving vehicles such as cars, ships, and airplanes, and individual users …
Amplitude modulation is a type of modulation where the carrier signal’s amplitude is varied in accordance with the information bearing signal. The amplitude modulated signal’s envelope or boundary embeds the information bearing signal. The total power of the transmitted signal varies with the modulating signal, whereas the carrier power remains constant. A nonlinear device combines …
Intersymbol interference is a signal distortion in telecommunication. One or more symbols can interfere with other symbols causing noise or a less reliable signal. The main causes of intersymbol interference are multipath propagation or non-linear frequency in channels. This has the effect of a blur or mixture of symbols, which can reduce signal clarity. If …
A phototransistor is a device that converts light energy into electric energy. Phototransistors are similar to photoresistors but produce both current and voltage, while photoresistors only produce current. This is because a phototransistor is made of a bipolar semiconductor and focuses the energy that is passed through it. Photons (light particles) activate phototransistors and are …
Voltage is the measurement for the electrical force between two points that drives the current. More specifically, voltage is the measure of the energy per unit charge that is equal to the electrical potential difference between two measured points. Volts are normally measured by a voltmeter. Voltage drop is the reduction in voltage in an …
In order to deter theft, the majority of major automobile manufacturers implement a car radio security code. When the car stereo is removed from a vehicle, the device will not be usable until the unlock or security code is entered by the car owner or authorized repair facility. Unfortunately, some models of cars and trucks …
A Bessel filter is a linear filter that is used in electronics and signal processing and has a flat group delay (also referred to as a maximally linear phase response). These filters are commonly used in audio crossover systems and preserve the wave shape of any filtered signals across the group delay in the passband. …
The symbol rate is the rate of state changes on a communications circuit. If a circuit can carry two tones per second, the circuit has a symbol rate of two. Circuits then use different modulation techniques to carry multiple bits per symbol. If the circuit is limited to two different tones, the first tone can …
QPSK (Quadrature Phase Shift Keying) is a phase modulation algorithm. Phase modulation is a frequency modulation version where the carrier wave’s phase is modulated to encode bits of digital information in each phase change. The “PSK” in QPSK refers to the use of Phased Shift Keying. Phased Shift Keying is a form of phase modulation …
Linear amplifiers are electronic circuits that have an output that is proportional to the input of the device while providing additional power to the load. A linear amplifier is normally a variant of a radio-frequency (RF) power amplifier and is used frequently in amateur radio and in laboratory and commercial audio equipment with an output …