Land Mobile & HF Radio

The land mobile radio (LMR) category includes a wide variety of wireless communication systems in the high frequency (HF: 3-30 MHz), very high frequency (VHF: 30 – 300 MHz) and ultra high frequency (UHF: 300 – 3,000 MHz) bands. LMR systems are typically used for two-way voice communications and low-bandwidth data transfer. Examples include walkie-talkies, citizen band (CB) radio, amateur radio and specialized mobile radio (SMR, also called trunked radio). High frequency (HF) radio systems support long-distance communications over tens to hundreds of kilometers, and have been employed as a communications option in rural and remote areas for decades.

Applications of LMR and HF radio systems in remote and off-grid areas include public and private two-way voice communication services; private voice and data services on a campus or industrial complex; low-bandwidth email, internet and bulletin board system (BBS) access; and public safety and security networks. Many systems are used to provide communication services to discrete user groups, while others, such as SMR, can support interconnection to public switched telephone networks.

Typical bandwidth for LMR is 15 – 30 KHz per analog voice channel (Ref). These systems are increasingly capable of supporting packetized data transfer as well as voice services. Common data transfer rates over packet radio are 1200 and 9600 bps, although technological developments are pushing these rates higher. For reference purposes, this is similar to the rate that fax machines can provide, and would not be appropriate for anything beyond email.

Important LMR and HF radio system components include portable (handheld) user terminals, mobile radio or base stations, repeaters, modems, antennas and switching or controller equipment. The systems typically operate on DC power. Transceivers (transmit and receive devices) often consume the bulk of the power in an installation, and power consumption is highest while transmitting (see Table below). When evaluating product specifications for a wireless transceiver it is important to note that the power consumption of the device is not the same as the transmit (Tx) or output power. The transmit power refers to the strength of the radiowave signal as it propagates in space away from the transmitting antenna. Power consumption is the rate of electrical current that the system draws in order to generate the radiowave.

Power consumption for LMR and HF radio systems varies widely by product and type of system. In general, the higher the transmit power (which is related to the range of the signal) the higher the energy consumption will be.

Typical Power Consumption of HF/VHF/UHF Radio Systems

Source: Icom, Kantronics and Symek product data sheets.

Related Web-based Resources

• Icom, Inc. (company site)
• Kantronics (company site)
• Symek (company site)