Land Mobile Radio Systems

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<p>National Communications System (NCS) ESF #2 Training Conference</p> <p>LAND MOBILE RADIO SYSTEMS AND HOW TO RESTORE THEMMajor Curtis BowersPlaquemines Parish Sheriffs Office 504-392-1652 June 21, 2007</p> <p>Class Topics</p> <p> Types of Radio Systems </p> <p>Simplex Trunking APCO Project 25</p> <p> Frequencies Getting a system back online Radio gateway devices</p> <p>Different Types of Radio Systems</p> <p>Conventional Systems Simplex Operation (Radio-to-Radio) Repeater</p> <p>Trunking Systems Single Site Multicast Simulcast Conventional Digital</p> <p>Conventional Systems Simplex Operation Transmissions are made over the same frequency Transmissions are from radio to radio no system infrastructure needed</p> <p>Conventional Systems</p> <p> Carrier Squelch - open to interference Private Line Code keeps radio signals on same frequency from keying into radio or opening the carrier squelch Interference audio is still present</p> <p>Conventional Systems</p> <p> What are the advantages of this type of system? Cost almost any radio will work, as long as frequency is correct Small number of users Small coverage area No infrastructure is needed</p> <p>Conventional Repeater Systems Repeaters boost transmission power for greater range Antennas are placed on towers for increase in coverage area</p> <p>400</p> <p>5 watts</p> <p>100 watts</p> <p>25 watts</p> <p>Conventional Repeater Systems Repeater systems improve portable and mobile talk-out and talk-in coverage A duplex system uses two frequencies. The radio transmits audio into the repeater and repeater sends out the audio at a higher wattage on a different frequency Antenna on a tower with a repeater gives a greater range Antenna on a tower with a pre-amp receive system increases talk-in coverage</p> <p>Trunking Systems Trunking systems consist of several repeaters controlled by computerized system System manages users, talkgroups, and repeaters</p> <p>RepeatersControl Channel</p> <p>Central Controller</p> <p>Trunking Systems Trunking systems can be a single site or consist of multiple sites over large regions Each repeater has its own frequency and one of these repeaters is a control channel Control channel manages information to and from the users radios With this information, channels (repeaters) are assigned to users for radio traffic Control channel is always communicating with affiliated radios Affiliated radios send talkgroup (TG) info to system</p> <p>Trunking Systems Voice Channel RequestPTT Request</p> <p>1 4 3Control Channel</p> <p>2</p> <p>Central Controller</p> <p>Trunking Systems There can be numerous talkgroups and users on this type of system Capacity is determined by number of channels (repeaters) the system has There can be numerous sites (towers) used on this type of system Size of system is limited to the number of frequencies the owner can obtain, the manufacture of the system, the version of system in service, and how much the owner can afford</p> <p>Trunking Systems Different types of multi-site systems:Multicast: The multiple broadcast of identical audio information on different frequencies from multiple, geographically separated sites Simulcast: The simultaneous broadcast of identical audio information on the same frequency from multiple, geographically separated sites</p> <p>Trunking Systems Multicast System ExampleSite 1 1 2CC VC</p> <p>Site 2 3 4 5CC VC VC</p> <p>Site 3 6 7 8CC VC VC</p> <p>Trunking Systems</p> <p>Site 1</p> <p>Site 2</p> <p>1 2 3CC VC VC</p> <p>4 5 6CC VC VC</p> <p>Site 3Multicast cells could be combinations of sites in what is also called a Simulcast configuration</p> <p>7 8CC VC</p> <p>Trunking Systems Simulcast System ExampleSite 1 1 2 3 4 5 6 7 8CC VC VC VC VC VCVC VC</p> <p>Site 2 1 2 3 4 5 6 7 8CC VCVC VC VC VCVC VC</p> <p>1 2 3 4 5 6 7 8CC VC VC VC VC VCVC VC</p> <p>Site 3</p> <p>Trunking Systems Simulcast Seamless CoverageSite 1 Site 2</p> <p>1 2 3 4 5 6 7 8CC VC VC VC VC VC VC VC</p> <p>2 1 2 3 4 5 6 7 8CC VC VC VC VC VC VC VC</p> <p>1 2 3 4 5 6 7 8CC VC VC VC VC VC VC VC</p> <p>Site 3</p> <p>Trunking Systems Trunking systems with multiple sites have a weak link in their operation; links must go back to the master site Links can be T-1 circuits or microwave links Multicast sites that lose their links go into site trunking and no longer communicate with other sites In a simulcast system, only the prime site will continue to operate; all other remote simulcast sites are off line until links are reestablished A simulcast cell can also go into site trunking</p> <p>Trunking Systems Analog operation Mix mode consisting of digital and analog resources APCO 25 systems digital only Digital is not a secure communication system, encryption is for secure communication</p> <p>Analog vs. DigitalBenefits of Digital Technologies Improved Audio Quality</p> <p>Good</p> <p>Digital</p> <p>Audio Quality</p> <p>Analog</p> <p>Poor Strong Signal Strength Weak</p> <p>Frequency Issues License for frequencies to be restored or used Special Temporary Authorization (STAs) obtained Equipment must match frequency range of system Service equipment, software, and hardware needed to tune equipment to frequencies to be restored Types of equipment needing tuning for frequencies: Combiners, duplexers, repeaters, tower top amp's, and radios</p> <p>Restoring a Communication System</p> <p> Survey what is left that still works or that can be put back in service What type of system will be initially put in service At tower sites you will need antennas, antenna mounts, antenna cable, cable connectors, tower climbing crew, and site master testing equipment</p> <p>Restoring a Communication System</p> <p> Determine how this equipment can be transported to the site If this is a remote site how will it be connected (linked) back to other sites: microwave, phone circuits, or broadband satellite Locate or identify a vendor or service shop that can perform many of these task for you</p> <p>Restoring a Communication System</p> <p> Installing a new communication system What does the supported agency need What type of technology will be used What is best for the agency being supported, not what the vendors want to sell</p> <p>Radio Gateways How will this device help Will it even work with the system or systems being connected Get permission before connecting systems together Set the rules for how this gateway channel or talkgroup will be used</p> <p>Radio Gateways</p> <p> When a problem arises with this connection, a contact person must be available 24 hrs a day Not always the best way to connect groups of users together</p> <p>Questions</p> <p>Any questions welcome</p> <p>Contact Information</p> <p>Major Curtis Bowers Plaquemines Parish Sheriffs Office 8344 Hwy 23 Belle Chasse, LA 70037 504-392-1652 office 504-812-9305 cell</p>


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