RG-58/U is a type of coaxial cable often used for low-power signal and RF connections. The cable has a characteristic impedance of either 50 or 52 Ω . "RG" was originally a unit indicator for bulk RF cable in the U.S. military's Joint Electronics Type Designation System . There are several versions covering the differences in core material (solid or braided wire) and shield (70% to 95% coverage).
26-560: The outside diameter of RG-58 is around 0.2 inches (5 mm). RG-58 weighs around 0.025 lb/ft (37 g/m), exhibits approximately 25 pF/ft (82 pF/m) capacitance and can tolerate a maximum of 300 V potential (1800 W). Plain RG-58 cable has a solid center conductor. The RG-58A/U features a flexible 7- or 19-strand center conductor. Most two-way radio communication systems, such as marine, CB radio , amateur , police, fire, WLAN antennas etc., are designed to work with
52-456: A specification or standard. They are designed as systems with all equipment matched to perform together. For example, a modern, local government two-way radio system in the US may be designed to provide 95% area coverage in an urban area. System designers use radio frequency models, terrain models, and signal propagation modeling software in an attempt to accurately estimate where radios will work within
78-612: A 50 Ω cable. RG-58 cable is often used as a generic carrier of signals in laboratories, combined with BNC connectors that are common on test and measurement equipment such as oscilloscopes . RG-58 in versions RG-58A/U or RG-58C/U was once widely used in "thin" Ethernet ( 10BASE2 ), for which it provides a maximum segment length of 185 meters. However, it has been almost completely replaced by twisted-pair cabling such as Cat 5 , Cat 6 , and similar cables in data networking applications. RG-58 cable can be used for moderately high frequencies. Its signal attenuation depends on
104-476: A Motorola system and the County of Riverside purchased a General Electric. In order to communicate, some patch or other custom-built link would have to be installed. Intercommunication was possible but not seamless. A by product of the work on Project 16 was the recognition that the problems of interagency cooperation inherent in the then standard allocations of separate frequencies to separate functions and agencies in
130-437: A broadcast receiver, which only receives transmissions. Two-way radios usually use a half-duplex communication channel, which permits two-way communication, albeit with the limitation that only one user can transmit at a time. (This is in contrast to simplex communication , in which transmission can only be sent in one direction, and full-duplex, which allows transmission in both directions simultaneously.) This requires users in
156-442: A defined geographic area. The models help designers choose equipment, equipment locations, antennas , and estimate how well signals will penetrate buildings. These models will be backed-up by drive testing and actual field signal level measurements. Designers adjust antenna patterns, add or move equipment sites, and design antenna networks in a way that will accomplish the intended level of performance. Many mobile and handhelds have
182-476: A fifteen-year life. Mobile radios are expected to last ten years. Walkie talkies typically last eight. In a State of California document, the Department of General Services reports expected service life for a communications console used in the Department of Forestry and Fire Protection is 10 years. Typical two-way radios work on fixed radio frequency channels, though some can scan multiple channels in order to find
208-406: A function of frequency. There are other factors that affect the range of a two-way radio such as weather, exact frequency used, and obstructions. APCO-16 In telecommunications , APCO-16 , (sometimes APCO Project 16 or Project 16 ) is a US standard for the characteristics and capabilities of public safety trunked radio systems . The standard development effort was started in
234-478: A group to take turns talking. The radio is normally in receive mode so the user can hear all other transmissions on the channel. When the user wants to talk, they press a " push-to-talk " button, which turns off the receiver and turns on the transmitter; when the button is released, the receiver is activated again. Multiple channels are provided so separate user groups can communicate in the same area without interfering with each other and some radios are designed to scan
260-451: A group while permitting the intercommunications between groups as controlled by a central "group assignment" controller. The extent of the scope of such intra unit coordination would be limited only by the design of the management structure involved and limitations of the addressing and control mechanism technology. A third LEAA grant funded Project 16B, "Draft System Implementation Plans for Participating Communities," which addressed how such
286-911: A limited duty cycle. Duty Cycle is the ratio of listening time to transmit time and is generally dependent on how well the transmitter can shed the heat from the heat sink on the rear of the radio. A 10% duty cycle (common on handhelds) translates to 10 seconds of transmit time to 90 seconds of receive time. Some mobile and base equipment is specified at different power levels – for example 100% duty cycle at 25 watts and 15% at 40 watts. In government systems, equipment may be replaced based on budgeting rather than any plan or expected service life. Funding in government agencies may be cyclical or sporadic. Managers may replace computing systems, vehicles, or budget computer and vehicle support costs while ignoring two-way radio equipment. Equipment may remain in use even though maintenance costs are unreasonable when viewed from an efficiency standpoint. One document says "seven years"
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#1732851892187312-740: A project to develop required capabilities and standards needed in trunked public safety two-way radio systems. The report defined proposed methods for frequency reuse, coordination, and interference reduction. The standards also gained acceptance in businesses such as Specialized Mobile Radio , utility communications systems, and refineries. The study concluded that those frequencies would be suitable for Public Safety mobile radio uses. The study recognized that certain technical problems like "picket fencing", foliage interference and abrupt signal fall out posed some minor problems, also addressed concerns about health effects from 800 MHz transmitters but did not reveal definitive findings. The availability of
338-432: A separate range of tone pitches, for example. Digital systems may communicate text messages from computer-aided dispatch (CAD). For example, a display in a tow truck may give a textual location for a call and any related details. The tow truck driver may press an acknowledge button, sending data in the opposite direction and flagging the call as received by the driver. They can be used for analog telemetry systems, such as
364-418: A valid transmission. In an analog, conventional system, (the simplest type of system) a frequency or channel serves as a physical medium or link carrying communicated information. The performance of a radio system is partly dependent on the characteristics of frequency band used. The selection of a frequency for a two-way radio system is affected, in part, by: The most common two-way radio systems operate in
390-408: Is applied to wired communication systems where the circuit can send information in one direction at a time but not both directions at the same time. Analog systems may communicate a single condition, such as water level in a livestock tank. A transmitter at the tank site continually sends a signal with a constant audio tone. The tone would change in pitch to indicate the tank's water level. A meter at
416-408: Is beyond the expected lifetime of walkie-talkies in police service. Batteries are cited as needing replacement more often. Twelve-year-old dispatch consoles mentioned in the same document were identified as usable. These were compared to problematic 21-year-old consoles used elsewhere in the same system. Another source says system backbone equipment like consoles and base stations are expected to have
442-513: The VHF and UHF parts of the radio spectrum . Because this part of the spectrum is heavily used for broadcasting and multiple competing uses, spectrum management has become an important activity of governments to regulate radio users in the interests of both efficient and non-interfering use of radio. Both bands are widely applied for different users. The useful direct range of a two-way radio system depends on radio propagation conditions, which are
468-706: The 1970s by the APCO , a trade association of mostly police and fire service providers. The program was funded by the Law Enforcement Assistance Administration (LEAA), a part of the US Department of Justice . APCO-16 describes such characteristics and capabilities as: With the Federal Communications Commission's pending release of the first 800 MHz band licenses, the LEAA funded
494-641: The Galvin Manufacturing Corporation in 1940 for use by the police and military during World War II , and followed by the company's 1943 introduction of the Walkie-Talkie, the best-known example of a two-way radio. The first truly mobile two-way radio equipment was developed in Australia in 1923 by Senior Constable Frederick William Downie of the Victorian Police. The Victoria Police were
520-656: The Public Safety Service might be solved by the use of digital addressing, trunking techniques. A follow-on project titled APCO Project 16A was funded by a second LEAA grant. It addressed a proposal to open the 800 MHz band. This program defined technical details such as "channel access time," "system growth capability," and "reliability." Project 16A identified the organizational advantages that would accrue from assigning individual unit addresses and adding another "group" address element. The group element would permit routine unit communications privacy among members of
546-425: The channels in order to find a valid transmission. Other two-way radio systems operate in full-duplex mode, in which both parties can talk simultaneously. This requires either two separate radio channels or channel sharing methods such as time-division duplex (TDD) to carry the two directions of the conversation simultaneously on a single radio frequency. The first two-way radio was an AM-only device introduced by
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#1732851892187572-1159: The first in the world to use wireless communication in cars, putting an end to the inefficient status reports via public telephone boxes which had been used until that time. The first sets occupied about half of the floor in the back seat of the Lancia patrol cars. In 1933, the Bayonne, New Jersey police department successfully operated a two-way system between a central fixed station and radio transceivers installed in police cars; this allowed rapidly directing police response in emergencies. Two-way radio systems can be classified in several ways depending on their attributes. In multi-channel systems, channels are used for separate purposes. Scan features are either not used or scan lists are intentionally kept short in emergency applications. Part of APCO Project 16 set standards for channel access times and delays caused by system overhead. Scan features can further increase these delays. One study said delays of longer than 0.4 seconds (400 milliseconds) in emergency services are not recommended. The term "half duplex"
598-503: The frequency, e.g. from 10.8 dB per 100 m (3.3 dB per 100 feet) at 50 MHz to 70.5 dB per 100 m (21.5 dB per 100 feet) at 1 GHz. This electronics-related article is a stub . You can help Misplaced Pages by expanding it . Two-way radio A two-way radio is a radio transceiver (a radio that can both transmit and receive radio waves ), which is used for bidirectional person-to-person voice communication with other users with similar radios, in contrast to
624-402: The livestock tank levels, as described above. Another possibility is the lubricating oil pressure in a transit bus engine, or the current speed of the bus. Analog conditions are translated into data words. Some systems send radio paging messages which can either 1) beep a paging receiver, 2) send a numeric message, or 3) send a text message. Engineered systems are designed to perform close to
650-477: The remote end would vary, corresponding to the tone pitch, to indicate the amount of water present in the livestock tank. Similar methods can be used to telemeter any analog condition. This type of radio system serves a purpose equivalent to a four-to-twenty milliampere loop . In the US, mid-band 72–76 MHz or UHF 450–470 MHz interstitial channels are often used for these systems. Some systems multiplex telemetry of several analog conditions by limiting each to
676-545: The significant additional spectrum and the long term possibility of the eventual collocation of nearly all Public Safety communications into one segment of the spectrum far outweighed these problems. While the program succeeded in creating basic performance standards and feature sets, it failed to create a signaling standard. The result: three companies built APCO Project 16 compliant systems but radios from each manufacturer were incompatible with one another. In California , for example, University of California, Riverside bought
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