Gibilisco - Wireless And Personal Communications Systems

A device consisting of a receiver and transmitter in the same case or enclosure is commonly used for wireless communications. This device is called a transceiver. It combines both the functions of receiving and transmitting signals, allowing for two-way communication in wireless systems.

A computer with a telephone modem is not a wireless device or system because it requires a physical connection to a telephone line in order to connect to the internet or make phone calls. The other options listed - SWL station, amateur radio station, and cordless phone set - are all wireless devices or systems that do not require a physical connection to function.

The correct answer is "a central computer in a local area network." A file server is a type of server that is responsible for storing, managing, and providing access to files within a local area network (LAN). It acts as a central computer that allows users to store and retrieve files from a shared storage location. Unlike the other options, which involve radio receivers, transmitters, or repeaters, a file server is specifically designed for network file sharing purposes.

The GPS (Global Positioning System) is a navigation system that uses satellite signals to determine the precise location of a receiver. It can be used to provide accurate directions and guidance to a motorist who is lost. By using GPS, the motorist can input their desired destination and receive turn-by-turn directions to help them navigate to their desired location. This can be particularly useful in unfamiliar areas or when the motorist is unsure of their current location. The other options mentioned in the question, such as improving LAN performance, increasing data speed in a wireless system, and minimizing noise in a wireless system, are not related to the primary purpose of GPS, which is navigation and location tracking.

In a cellular network, the region covered by a single base station is called a cell. Each cell is a geographical area served by a base station, and it is the basic building block of a cellular network. The purpose of dividing the network into cells is to efficiently allocate and manage the available radio frequency resources. By dividing the coverage area into smaller cells, the network can support a larger number of users and provide better signal quality and capacity.

In the United States, a license is required for transmitting on amateur radio frequencies. This means that individuals who want to operate a radio transmitter on these frequencies need to obtain a license from the Federal Communications Commission (FCC). This requirement is in place to ensure that operators have the necessary knowledge and skills to use the radio frequencies responsibly and safely. It also helps to prevent interference with other radio services and ensures that operators understand the regulations and rules associated with amateur radio operation.

An advantage of a cell phone over a hard-wired phone is the fact that it offers better mobility. Unlike a hard-wired phone, a cell phone allows individuals to make and receive calls from anywhere as long as there is network coverage. This mobility enables users to stay connected and accessible even when they are on the move, providing them with the flexibility to communicate while traveling or away from their home or office.

In a two-way communications system with full duplex, both parties have the ability to transmit and receive data simultaneously. This means that either party can hear the other at all times. This is possible because the system allows for two-way communication without any interruptions or restrictions on listening or speaking.

For a receiver to render a digitally encrypted signal intelligible, it needs a decryption key. This key is necessary to decode the encrypted signal and convert it back into its original form. Without the decryption key, the receiver would not be able to understand the encrypted signal and it would remain unintelligible.

Mil spec, short for military specification, refers to a set of standards and requirements that must be met by equipment used by the military. In the context of security, mil spec refers to the highest obtainable level of security. This means that a system or device that meets mil spec requirements has undergone rigorous testing and meets the strictest standards to ensure its security. It is considered to be the most secure option available.

End-to-end encryption provides a higher degree of security than wireless-only encryption. This is because end-to-end encryption ensures that the data being transmitted is encrypted from the sender to the recipient, making it difficult for any unauthorized party to intercept and access the information. In contrast, wireless-only encryption only encrypts the data while it is being transmitted over the wireless network, leaving it vulnerable to attacks or interception during other stages of communication. Therefore, end-to-end encryption offers a more comprehensive and secure approach to protecting data in a wireless LAN.

A noise blanker is a device used in radio communications to reduce or eliminate unwanted noise or interference. It works by detecting sudden increases in signal strength, which are often caused by noise, and then temporarily muting or blanking the audio output. By doing so, the noise blanker improves the quality of radio reception by reducing background noise and allowing for clearer communication.

The horizontal axis of a spectrum analyzer represents the frequency. A spectrum analyzer is a device used to measure and display the frequency spectrum of a signal. It shows the distribution of energy across different frequencies in the signal being analyzed. By representing the frequency on the horizontal axis, the spectrum analyzer allows for easy identification and analysis of the different frequency components present in the signal.

A network that employs one central computer and multiple personal computers is called a client-server network. In this type of network, the central computer, known as the server, provides services and resources to the personal computers, known as clients. The server manages the network, stores data, and controls access to shared resources, while the clients rely on the server for these services. This type of network architecture is commonly used in businesses and organizations where centralized control and management are important.

Infrared and optical wireless links work best when there is a direct line of sight between the transmitter and receiver. This is because infrared and optical signals are easily obstructed by physical objects such as walls or obstacles. Therefore, having a clear line of sight ensures that the signals can travel without interference and maintain a strong connection.

A LAN in which each computer has more or less equal status and stores its own data is known as a peer-to-peer LAN. In this type of network, there is no central server or hierarchy, and all computers can directly communicate and share resources with each other. This allows for decentralized data storage and sharing, making it suitable for small-scale networks where all computers have similar roles and responsibilities.

As the data speed increases in a wireless system, all other factors being equal, the signal bandwidth increases. This means that the range of frequencies over which the signal is transmitted also increases. This is because higher data speeds require a wider range of frequencies to accommodate the increased amount of information being transmitted. Therefore, as the data speed increases, the signal bandwidth must also increase to support the higher data rate.

Infrared waves are longer than visible-light waves. In the electromagnetic spectrum, waves with longer wavelengths have lower frequencies and less energy. Visible-light waves have shorter wavelengths and higher frequencies compared to infrared waves. Infrared waves are commonly associated with heat because they are absorbed by objects and cause them to warm up. However, it is important to note that infrared waves are not solely heat rays but also have various applications in communication, imaging, and remote sensing.

A radio signal is considered to be in the shortwave band if its frequency is 5 MHz. Shortwave signals have wavelengths between 10 and 100 meters, which corresponds to frequencies between 3 and 30 MHz. Therefore, 5 MHz falls within this range and is considered to be in the shortwave band.

A conventional hard-wired telephone affords better privacy because the communication is transmitted through physical wires, making it more difficult for others to intercept or eavesdrop on the conversation. Unlike cell phones, which use wireless signals that can be intercepted or monitored, hard-wired phones provide a more secure and private means of communication.

In a geostationary satellite link, the repeater is located over the equator. This is because geostationary satellites are positioned in orbit around the Earth at a specific altitude above the equator. By placing the repeater over the equator, it ensures that the satellite remains in a fixed position relative to the Earth's surface, allowing for continuous and uninterrupted communication between the satellite and the ground stations. This positioning is crucial for providing reliable and stable satellite communication services.

Eavesdropping of a wireless link is difficult or impossible to detect because wireless signals can be intercepted without leaving any physical trace. Unlike wired connections, where physical access is required to tap into the communication, wireless signals can be intercepted from a distance. Additionally, encryption and decryption keys are not mentioned in the question, so they are not relevant to the explanation.

Shortwave radio signals refer to signals with wavelengths ranging from 10 meters to 100 meters. This range is considered short compared to other radio waves, such as medium wave or long wave. Shortwave signals are commonly used for long-distance communication due to their ability to travel long distances by bouncing off the ionosphere.

In a LEO (Low Earth Orbit) satellite system, the repeaters are located in space. This is because LEO satellites are positioned in low Earth orbits, typically between 160 and 2,000 kilometers above the Earth's surface. By placing the repeaters in space, they can effectively relay signals between ground stations and provide communication coverage over a wide area. This allows for efficient and reliable communication services, such as internet connectivity, telephony, and data transmission, to be provided to users on the ground.

LEO satellite systems have the advantage of providing coverage to regions near the geographic poles, which geostationary satellite systems cannot do. This is because LEO satellites orbit much closer to the Earth's surface, allowing them to provide coverage to areas that are not easily accessible by geostationary satellites, which remain fixed above the equator. This advantage makes LEO satellite systems more suitable for applications that require coverage in polar regions, such as scientific research, polar expeditions, and military operations.

Reducing the temperature to very low values can minimize noise in a wireless receiver because at lower temperatures, the thermal noise generated by the receiver's components decreases. This is known as Johnson-Nyquist noise, which is directly proportional to temperature. By lowering the temperature, the random fluctuations in the receiver's circuitry are reduced, resulting in less noise interference and improved signal quality.

It is illegal to advertise used cars for sale using a ham radio station in the United States because ham radio stations are only allowed to be used for amateur radio communications. Advertising used cars for sale is considered a commercial activity and is not permitted on amateur radio frequencies.

Radiolocation refers to the use of direction-finding equipment to determine the location of a radio transmitter. This technique involves measuring the angle of arrival of the radio signals from different locations and using triangulation to calculate the latitude and longitude of the transmitter. The other options, IR wireless, the Global Positioning System, and packet radio, do not specifically involve the use of direction-finding equipment for determining the location of a radio transmitter.

As the noise level in a wireless system increases, stronger incoming signals are needed to overcome it. This is because the noise interferes with the signal, making it weaker and harder to detect. In order to overcome the noise and maintain a reliable signal, stronger signals are required.