Radio modems

Radio modems are modems that transfer data wirelessly across a range of up to tens of kilometers. Using radio modems is a modern way to create Private Radio Networks (PRN). Private radio networks are used in critical industrial applications when real-time data communication is needed. Radio modems enable the user to be independent of telecommunication or satellite network operators. In most cases, users use licensed frequencies either in the UHF or VHF bands. In certain areas licensed frequencies may be reserved for a given user, thus ensuring that there is less likelihood of radio interference from other RF transmitters. Also, license-free frequencies are available in most countries, enabling easy implementation, but at the same time, other users may use the same frequency, thus making it possible that a given frequency is blocked.

Typical use cases

Typical users for radio modems are Land survey, differential GPS, fleet management applications, SCADA applications (utility distribution networks), automated meter reading (AMR), telemetry applications, and many more. Since applications usually require high reliability of data transfer and very high uptime, radio performance plays a key role. Factors influencing radio performance are antenna height and type, the sensitivity of the radio, the output power of the radio, and the complete system design.

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What is a radio modem?

  • The initial investment for a radio modem is relatively high (2 to 3 times the cost of a phone modem), but the cost is somewhat offset by the fact that once installed, the user does not incur additional toll charges for each connection. A mixed communication mode may also be a viable alternative where a remote radio link is connected to a remotely located phone line. The modems are divided into types according to modulation and frequency range

Frequency Ranges (modems operate unlicensed in the following ISM bands)

  • 915 MHz (902-928 MHz)
  • 2.4 GHz (2400-2483.5 MHz)
  • 5.8 GHz (5728-5850 MHz)

For interfacing with GPS receivers, the modems have to be RS-232 compatible.

Suggested minimum requirements

  • Range up to 60km (Line-of-sight)
  • Low power consumption (2-5W)
  • Light weight (0.5-1.0 kg)
  • High effective data throughput (2.4-19.2kbps)
  • Environmentally durable (temperature, humidity, shock resistant)
  • RS-232 compatible