Omni Antenna
An omni, or “omni-directional” antenna, is made from a dipole antenna wire that has had its two ends bent into a curved shape. This antenna resembles the shape of the letter “S.” By bending the poles of the dipole antenna, the maximum receiving range is reduced, but nearby omni-directional signal strength is improved.
An omni antenna is used in 2 way radio situations where all communication will will take place near one small area, such as a base or outpost. The omni design allows radios in any direction near the base station to be easily reached. Cell phone towers also commonly use omni antennas. This enables a cell phone radio signal to reach a nearby tower from any direction, and even if the user is moving.
Parabolic Antenna
A parabolic antenna design combines a simple dipole with a semi-circular dish. Just as a magnifying glass can focus light to a precise point, the curved dish reflects radio signals directly onto the dipole. The most common example of a parabolic antenna is the home satellite dish, however the design can be used in other two-way radio applications as well.
Parabolic antennas are used for two-way communication over extremely long distances, and are usually able to transmit farther than a Yagi design. The parabolic antenna type is only useful if the exact location of the target receiver is known. Parabolic antennas are frequently used for two-way satellite links, long-range wireless Internet, and two-way radio communication between fixed stations.
2013年1月6日星期日
The History of Two-Way Radios
The Beginning
Besides the electric telegraph, which was mainly used to send Morse code messages, the first advances in 2 way radios are widely credited to Hertz. In 1885, Hertz conducted experiments proving that electricity can be transmitted as electromagnetic waves, which he concluded could be sent and received, though saw no real potential in them. Though, in 1891, the first radios, or what we would consider wireless telegraphs today, began to appear commercially on ships. By 1893, Nikola Tesla had successfully demonstrated the transfer of electromagnetic energy wirelessly. Quite simply, he made a radio.
Broadcasting
In 1896, Guglielmo Marconi patented his radio apparatus and established his own company distributing them by the next year. By 1901, Marconi had sent the first trans-Atlantic signal from Ireland to Canada. By 1902, an amateur known as “Ham” published an article on “How to Construct an Efficient Wireless Telegraphy Apparatus at Small Cost,” in “Scientific American.” Since there was no regulation on ham radio broadcasts until 1912, amateur broadcasting flourished. The U.S. government shut down all amateur radio stations in 1017 as the nation entered WWI.
Advances
In 1891, experiments into the alternator-transmitter, or “continuous-wave” transmitters, began. Over a 20-year period this transmitter was refined and gave way to another model known as the arc-transmitter, and though less refined, it was more compact. This period also introduced vacuum-tube technology, which would give way to the resurgence of civilian radio broadcasts with a significantly longer range. During the first World War, these advancements in radio transmissions would allow communications with pilots as well as military broadcasts, which previously required the pilot to land to deliver a message or for messages to literally be dropped from the plane.
Uses
The first practical use of the two-way radio was set forth in 1890, replacing carrier pigeons and flags as a form of communication, on ocean ships. This increased both ease of communication, and safety, though it was still fairly limited. In 1921 Victorian police were the first to implement the use of wireless communication in patrol cars, which initially took up the entire back seat. Previous to this, police transmissions were made on public telephones. By 1933, the Beyonne, New Jersey, police department implemented a two-way radio system between police cars and a central station for better response in emergencies. This technology was also used during World War II for air and ground troops alike.
Today they are used in nearly every industry from aviation to commercial transport, military, retail, rehabilitation, public safety, security, and fire and emergency services, just to name a few.
Modern 2 Way Radios
The original two-way radios were only able to broadcast one signal at a time, called “simplex” mode, thus you could only send or receive a signal at a time. It wasn’t until “full duplex” was available that transmitters could be tuned to different frequencies that signals could be easily broadcast in two-way form used in personal, commercial and military facets alike.
This technology has progressed to the point of being so user friendly that nearly any individual can learn how to use a two-way radio easily, professionals and children alike. The modern two-way radio is so common that many cell phone companies have been incorporating them into their products for years, and many consider cell phones to be an extension of the inventions tested and created by the Marconi company and Bell Labs back in the 1920s, mainly their car telephone system, a voice-based radio telephone.
Besides the electric telegraph, which was mainly used to send Morse code messages, the first advances in 2 way radios are widely credited to Hertz. In 1885, Hertz conducted experiments proving that electricity can be transmitted as electromagnetic waves, which he concluded could be sent and received, though saw no real potential in them. Though, in 1891, the first radios, or what we would consider wireless telegraphs today, began to appear commercially on ships. By 1893, Nikola Tesla had successfully demonstrated the transfer of electromagnetic energy wirelessly. Quite simply, he made a radio.
Broadcasting
In 1896, Guglielmo Marconi patented his radio apparatus and established his own company distributing them by the next year. By 1901, Marconi had sent the first trans-Atlantic signal from Ireland to Canada. By 1902, an amateur known as “Ham” published an article on “How to Construct an Efficient Wireless Telegraphy Apparatus at Small Cost,” in “Scientific American.” Since there was no regulation on ham radio broadcasts until 1912, amateur broadcasting flourished. The U.S. government shut down all amateur radio stations in 1017 as the nation entered WWI.
Advances
In 1891, experiments into the alternator-transmitter, or “continuous-wave” transmitters, began. Over a 20-year period this transmitter was refined and gave way to another model known as the arc-transmitter, and though less refined, it was more compact. This period also introduced vacuum-tube technology, which would give way to the resurgence of civilian radio broadcasts with a significantly longer range. During the first World War, these advancements in radio transmissions would allow communications with pilots as well as military broadcasts, which previously required the pilot to land to deliver a message or for messages to literally be dropped from the plane.
Uses
The first practical use of the two-way radio was set forth in 1890, replacing carrier pigeons and flags as a form of communication, on ocean ships. This increased both ease of communication, and safety, though it was still fairly limited. In 1921 Victorian police were the first to implement the use of wireless communication in patrol cars, which initially took up the entire back seat. Previous to this, police transmissions were made on public telephones. By 1933, the Beyonne, New Jersey, police department implemented a two-way radio system between police cars and a central station for better response in emergencies. This technology was also used during World War II for air and ground troops alike.
Today they are used in nearly every industry from aviation to commercial transport, military, retail, rehabilitation, public safety, security, and fire and emergency services, just to name a few.
Modern 2 Way Radios
The original two-way radios were only able to broadcast one signal at a time, called “simplex” mode, thus you could only send or receive a signal at a time. It wasn’t until “full duplex” was available that transmitters could be tuned to different frequencies that signals could be easily broadcast in two-way form used in personal, commercial and military facets alike.
This technology has progressed to the point of being so user friendly that nearly any individual can learn how to use a two-way radio easily, professionals and children alike. The modern two-way radio is so common that many cell phone companies have been incorporating them into their products for years, and many consider cell phones to be an extension of the inventions tested and created by the Marconi company and Bell Labs back in the 1920s, mainly their car telephone system, a voice-based radio telephone.
How to Charge a Cobra CTX90 Two-Way Radio
The Cobra CTX90 is a 2 way radio, also commonly referred to as a walkie talkie. It is powered by four rechargeable AA batteries, which can be recharged while still housed inside the hand set. These radios are sold with a Y-shaped power adapter that can charge two radios at the same time.
1 Plug the plug end of the AC power adapter into a working electrical outlet.
2 Insert one of the power adapter jacks into the charging outlet on the bottom of one of the Cobra CTX90 handsets.
3 Insert the second power adapter jack into the charging outlet on the bottom of the other handset.
4 Allow the batteries to charge overnight or until they become fully charged. Remove the handsets from the power adapter.
1 Plug the plug end of the AC power adapter into a working electrical outlet.
2 Insert one of the power adapter jacks into the charging outlet on the bottom of one of the Cobra CTX90 handsets.
3 Insert the second power adapter jack into the charging outlet on the bottom of the other handset.
4 Allow the batteries to charge overnight or until they become fully charged. Remove the handsets from the power adapter.
Parts of a Two-Way Radio
Transmitter
The transmitter creates the outgoing radio signals that allow two-way radios to communicate, a process known as propagation. Essentially, the transmitter takes a very simple signal produced within the radio by electric pulses that have been created from the user’s voice, and enhances them so they can be sent out to a communication tower or other radio.
Antenna
The antenna helps the transmitter send out its signal, and picks up other incoming signals with the help of a receiver. Without the antenna, the range for mobile 2 way radios would be virtually nonexistent.
Speaker
The speaker enables the user to speak into the radio and have the sounds converted to radio signals that can be sent through radio waves. Without the speaker, the radio would not be two-way at all, although there are other secondary devices that help the speaker both produce incoming sound and convert outgoing sound. When signals are incoming, the speaker takes the radio wave and converts it into sound, often with the help of an amplifier to enhance the audio. When signals are outgoing, the speaker must convert sound waves into radio waves that can be broadcast by the transmitter.
Range
There are two types of two-way radio communication, known as Repeat and Simplex. Repeat involves the use of a nearby radio tower or repeater, which takes the radio signal and propagates it even further, allowing the signal to travel miles in search of the correct person, usually in a format that most two-way radios can pick up. The exact distance depends on the power of the radio, but this method is always the most far-reaching and is used when one user is not sure where the other user is. Simplex is “simply” two radios talking to one another without the use of a repeater, which means they must be far closer together.
Tone Control: Encoder/Decoder
Many two way radios also have an encoder and decoder that allow users to privatize signals, known as tone control or private line. In PL mode, a two-way radio waits for only one type of tone, and will only activate if it picks up that particular tone. Another person trying to reach either one of the radios with a different tone will not succeed. The tone itself is basically a subaudible noise included with the transmission that acts as a type of authorization code.
The transmitter creates the outgoing radio signals that allow two-way radios to communicate, a process known as propagation. Essentially, the transmitter takes a very simple signal produced within the radio by electric pulses that have been created from the user’s voice, and enhances them so they can be sent out to a communication tower or other radio.
Antenna
The antenna helps the transmitter send out its signal, and picks up other incoming signals with the help of a receiver. Without the antenna, the range for mobile 2 way radios would be virtually nonexistent.
Speaker
The speaker enables the user to speak into the radio and have the sounds converted to radio signals that can be sent through radio waves. Without the speaker, the radio would not be two-way at all, although there are other secondary devices that help the speaker both produce incoming sound and convert outgoing sound. When signals are incoming, the speaker takes the radio wave and converts it into sound, often with the help of an amplifier to enhance the audio. When signals are outgoing, the speaker must convert sound waves into radio waves that can be broadcast by the transmitter.
Range
There are two types of two-way radio communication, known as Repeat and Simplex. Repeat involves the use of a nearby radio tower or repeater, which takes the radio signal and propagates it even further, allowing the signal to travel miles in search of the correct person, usually in a format that most two-way radios can pick up. The exact distance depends on the power of the radio, but this method is always the most far-reaching and is used when one user is not sure where the other user is. Simplex is “simply” two radios talking to one another without the use of a repeater, which means they must be far closer together.
Tone Control: Encoder/Decoder
Many two way radios also have an encoder and decoder that allow users to privatize signals, known as tone control or private line. In PL mode, a two-way radio waits for only one type of tone, and will only activate if it picks up that particular tone. Another person trying to reach either one of the radios with a different tone will not succeed. The tone itself is basically a subaudible noise included with the transmission that acts as a type of authorization code.
Two Way Radio Instructions
Setting the channels and codes
Turn on the 2 way radios and set both units to the same channel using the channel selector knob usually found on top of each radio near the antenna. If your radios are equipped with a security feature, enter the numeric code using the keypad. You can then adjust the volume to a comfortable listening level or plug in a set of earphones or headphones for added privacy.
Range, line of sight
Bear in mind that two-way radios operate on a UHF band (Ultra High Frequency), which is a microwave that sends signals over a limited range. Unlike cell phones, which bounce radio signals off cell towers so two people can talk over great distances, two-way radios send signals directly between each other. Most radios available for consumer use have an effective communication range of 5-10 miles, which can vary with weather conditions.
You’ll also enjoy better reception if there are no major physical obstacles between the radios. Outdoor reception between two radios 500 feet apart will be superior to indoor reception between a radio on the first floor of a skyscraper and a radio on the 40th floor of the same building.
Communicating over the air
If your radio uses a push-to-talk transmitter, you’ll need to depress and hold the button when you wish to communicate with another person. It is helpful to use a verbal code that lets the other person know when you are finished transmitting. The standard code is to say the word “over,” which is short for “over to you,” to let the other person know you are finished speaking and he should respond. “Over and out” is an acknowledgment that the communication is finished and you are signing off the radio.
More expensive two-way radios come with two radio transmitters and are known as full-duplex radios. These allow the users to talk and listen at the same time without pushing and holding transmitter buttons since two separate transmitters are employed in each radio. This technology is similar to cell phone transmissions.
Turn on the 2 way radios and set both units to the same channel using the channel selector knob usually found on top of each radio near the antenna. If your radios are equipped with a security feature, enter the numeric code using the keypad. You can then adjust the volume to a comfortable listening level or plug in a set of earphones or headphones for added privacy.
Range, line of sight
Bear in mind that two-way radios operate on a UHF band (Ultra High Frequency), which is a microwave that sends signals over a limited range. Unlike cell phones, which bounce radio signals off cell towers so two people can talk over great distances, two-way radios send signals directly between each other. Most radios available for consumer use have an effective communication range of 5-10 miles, which can vary with weather conditions.
You’ll also enjoy better reception if there are no major physical obstacles between the radios. Outdoor reception between two radios 500 feet apart will be superior to indoor reception between a radio on the first floor of a skyscraper and a radio on the 40th floor of the same building.
Communicating over the air
If your radio uses a push-to-talk transmitter, you’ll need to depress and hold the button when you wish to communicate with another person. It is helpful to use a verbal code that lets the other person know when you are finished transmitting. The standard code is to say the word “over,” which is short for “over to you,” to let the other person know you are finished speaking and he should respond. “Over and out” is an acknowledgment that the communication is finished and you are signing off the radio.
More expensive two-way radios come with two radio transmitters and are known as full-duplex radios. These allow the users to talk and listen at the same time without pushing and holding transmitter buttons since two separate transmitters are employed in each radio. This technology is similar to cell phone transmissions.
How a Two Way Radio Operates
Uses of 2 Way Radios
Since two-way radios can both transmit and receive they are a popular form of communication. Many families with younger children have opted for Family Service Radio, an improved walkie talkie system, on family outings to places like amusement parks because they are simpler for a small child to operate than a cell phone. These improved walkie talkies are also very popular with businesses where different departments can communicate with each other.
Receiving
The most commonly used mode of a two-way radio is the receive mode. When receiving, the radio is listening for a certain radio frequency. When a signal is detected, it is received on the units antenna, where is is routed to a amplifier and a circuit called a mixer. The mixer takes another fixed radio frequency and mixes it with the one that was received, the result is a lower radio frequency, usually called a I.F. or intermediate frequency.
This intermediate frequency is amplified and fed to another mixer, which will convert the IF down to an audio signal. The audio signal is amplified and fed to a volume control and then to a speaker or headphone jack for the user to listen to the audio.
Transmitting
Transmitting is receiving in reverse. Users normally have to push a button, called a transmit button, to place the radio into a transmit mode. Once the radio is in transmit mode, you talk into the microphone. Your voice audio is then amplified and sent through a mixer, turning it into an intermediate frequency.
The IF is then amplified and routed to another mixer, the frequency of which was chosen for the selected channel that you wish to transmit on. The resulting frequency is now a radio frequency that is sent to another amplifier and then routed to the radios antenna, where it propagates out to the atmosphere and to your intended user.
Since two-way radios can both transmit and receive they are a popular form of communication. Many families with younger children have opted for Family Service Radio, an improved walkie talkie system, on family outings to places like amusement parks because they are simpler for a small child to operate than a cell phone. These improved walkie talkies are also very popular with businesses where different departments can communicate with each other.
Receiving
The most commonly used mode of a two-way radio is the receive mode. When receiving, the radio is listening for a certain radio frequency. When a signal is detected, it is received on the units antenna, where is is routed to a amplifier and a circuit called a mixer. The mixer takes another fixed radio frequency and mixes it with the one that was received, the result is a lower radio frequency, usually called a I.F. or intermediate frequency.
This intermediate frequency is amplified and fed to another mixer, which will convert the IF down to an audio signal. The audio signal is amplified and fed to a volume control and then to a speaker or headphone jack for the user to listen to the audio.
Transmitting
Transmitting is receiving in reverse. Users normally have to push a button, called a transmit button, to place the radio into a transmit mode. Once the radio is in transmit mode, you talk into the microphone. Your voice audio is then amplified and sent through a mixer, turning it into an intermediate frequency.
The IF is then amplified and routed to another mixer, the frequency of which was chosen for the selected channel that you wish to transmit on. The resulting frequency is now a radio frequency that is sent to another amplifier and then routed to the radios antenna, where it propagates out to the atmosphere and to your intended user.
2013年1月4日星期五
How Do I Get More Range Out of My Two Way Radio?
Better Antennae
Replacing the antennae on two-way radios with an antennae that has more gain immediately increases the range for 2 way radio communication in an area. Gain constitutes the area over which the receiver from one radio connects to the receiver of another radio. Better gain means that the general area that two-way radios reach is bigger, broader and more complete, resulting in clearer reception between radios. Gain is measured in decibels, which is represented by “dB.” The best gain is 10 dB; the worst gain is 0 dB.
Stronger Radios
The antennae is only half of the equation. Something must push the signal through the antennae. That power is generated by the two-way radio itself. While a bad antennae can make even the strongest two-way radio relatively useless, a high-quality two-way radio with a good antennae provides the best range. A GMRS radio, which stands for the General Mobile Radio Service, has a government-provided land-mobile radio service, which helps facilitate short-distance communication between people using these particular two-way radios. These radios are typically more powerful than most. The more watts and channels a two-way radio has, the stronger it will be.
Battery Power
Two-way radios stocked with fully charged AA or AAA batteries are integral to achieving the best range. Low batteries result in a weaker signal and affect the radio’s range. Make sure the batteries have been fully charged or replaced each time you use the radios. It’s a good idea to have a spare, fully charged battery on hand or a fresh pack of disposable batteries to maintain communication.
Replacing the antennae on two-way radios with an antennae that has more gain immediately increases the range for 2 way radio communication in an area. Gain constitutes the area over which the receiver from one radio connects to the receiver of another radio. Better gain means that the general area that two-way radios reach is bigger, broader and more complete, resulting in clearer reception between radios. Gain is measured in decibels, which is represented by “dB.” The best gain is 10 dB; the worst gain is 0 dB.
Stronger Radios
The antennae is only half of the equation. Something must push the signal through the antennae. That power is generated by the two-way radio itself. While a bad antennae can make even the strongest two-way radio relatively useless, a high-quality two-way radio with a good antennae provides the best range. A GMRS radio, which stands for the General Mobile Radio Service, has a government-provided land-mobile radio service, which helps facilitate short-distance communication between people using these particular two-way radios. These radios are typically more powerful than most. The more watts and channels a two-way radio has, the stronger it will be.
Battery Power
Two-way radios stocked with fully charged AA or AAA batteries are integral to achieving the best range. Low batteries result in a weaker signal and affect the radio’s range. Make sure the batteries have been fully charged or replaced each time you use the radios. It’s a good idea to have a spare, fully charged battery on hand or a fresh pack of disposable batteries to maintain communication.
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