Codan Radio Transportable Radio Systems User Guide - Manual (Page 6)

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2.3.2 Vehicular Repeater
A vehicular repeater is a specialized radio repeater mounted in a vehicle that is used in conjunction with a mobile
radio to effectively expand the range of a portable radio in the fi eld. To illustrate this concept, an offi cer leaves his
vehicle and begins transmitting on his portable radio. The 3–5 Watt portable radio signal is boosted through the
vehicular repeater, thus enabling transmission at much greater distances. For in building or tunnel scenarios, the
vehicular repeater can improve the local communications in an emergency response. The vehicular repeater typically
is not limited by a power source and is highly mobile. However, it is limited by its ability to be moved from location to
location and used in confi ned or remote environments.
2.4 Base Stations
Base station radio systems are used to communicate between a
dispatch/command center and mobiles or portable-equipped
radio users in the fi eld. Base stations typically need to communicate
on multiple channels and frequently the radio itself needs to be
physically located at a remote location so as to provide better
radio coverage.
Digital base station radios can support either secure or clear digital
mode operation (encrypted or non- encrypted) using AES 256-bit
or DES-OFB 64-bit encryption modules compliant to the security
requirements of FIPS 140-2. Digital base stations have the ability to
automatically detect and differentiate between analog and digital
as well as encrypted or non-encrypted signals.
A local or wide area network can be used to link the dispatcher/command center and the base station site. Using the
P25 Digital Fixed Station Interface (DFSI) standard, an all digital (optionally encrypted) communication path can be
created from the portable to the dispatch center connected to the base station.
2.5 Benefits of a Transportable Radio
Normally, a repeater system is a fi xed installation used in combination with base stations and other equipment –
collectively known as “infrastructure”. One or more repeaters and base stations can be used to provide reliable wide
area coverage for the users in the fi eld. However, due to the physical limitations of installing “infrastructure equip-
ment” permanently in locations that are appropriate for housing communications equipment (radio towers, building
tops, mountains, etc.) there will always be areas that are not adequately covered. This may be due to being beyond
the coverage area of the system or working inside a large building that provides challenges for signal penetration
(very common in most urban areas).
In these areas of little or no radio coverage, a Transportable Radio can be very benefi cial in bringing the coverage
strengths found in a normally fi xed piece of infrastructure equipment to the scene of operations. By providing the
users on-scene with a local repeater, the communications between those fi rst responders on-scene can be very
effective. Whether the Transportable Radio is a small, low-power, tactical unit or a large, high-power, multi-agency/
multi-band system providing interoperability, a well planned Transportable Radio system will be a very effective tool
for all users that are operating in an area that typically would not have any radio coverage at all.
2.6 Components of a Transportable Radio
The following diagram and subsections overview the components of a Transportable Radio. Comprehensive details
on each component are provided in Chapter 4.
2.6.1 Transmitters and Receivers (TX/RX)
The transmitter (TX) and receiver (RX) are the key components of a Transportable Radio system. A repeater, whether
permanently installed infrastructure equipment or a Transportable Radio, will always have a Transmitter and
Receiver that are separate from each other. Further to this, the Transmitter and Receiver will each have their own
frequency. A repeater may not have the same Transmit and Receive frequency.
The Transmitter in a repeater system is designed to be capable of transmitting on only the desired frequency and not
broadcast excessive noise and signals on other frequencies that may be operating in the area. Typically a repeater
transmitter is higher power than a Portable or Mobile Radio, but it does not have to be. Remember that the location
of the repeater and its antenna is as important as the radiated power of the repeater itself. Optional an amplifi er
may be added to the transmitter to provide higher output power. For transportable radios this is typically less than
50 Watts due to proximity of the users and current consumption.
The Receiver in a repeater system is designed to be highly sensitive to low signal strengths so that users in the fi eld
with low power radio equipment such as portable radios, can communicate with the repeater. However, the repeater
receiver must also be capable of rejecting all the other signals that it may hear on adjacent channels. This is what
makes a repeater receiver different from a portable or mobile radio.
Battery
Solar Panel
Antennas – See section 2.6.3
Repeater consists of:
–Tx, Rx and Amplifi er – See section 2.6.1
–Duplexer - See section 2.6.2
Common Layout of a Transportable
Repeater System
Power Supplies – See section 2.6.5
Enclosures – See section 2.6.4
Enclosure for Repeater
Base Station Radio System