The high frequency band is very popular with military operators, who can take advantage of direct, long-distance (often inter-continental) communications and the NVIS technology of utilizing the ionosphere to overcome line of sight VHF/UHF limitations. International shortwave broadcasting utilizes this set of frequencies, as well as a number of "utility" users (marine, aviation, military, and diplomatic interests). The development of Automatic Link Establishment technology based on MIL-STD-188-141A and MIL-STD-188-141B for automated connectivity and frequency selection, along with the high costs of satellite usage, makes HF radios a cost effective communications. The development of higher speed modems such as those conforming to MIL-STD-188-110B which support data rates up to 9600 bit/s has also increased the usability of HF for data communications. Other standards development such as STANAG 5066 provides for error free data communications through the use of ARQ protocols. ITO offers a system which allows telephone to radio ability and the ability to track all radios and locate emergency beacon calls. Tactical Operations Centers (TOC) can view the location of all radios via computer and respond to emergency calls with exact knowledge of the caller's location.
VHF propagation characteristics are ideal for short-distance terrestrial communication, with a range generally somewhat farther than line-of-sight from the transmitter. Unlike high frequencies (HF), the ionosphere does not usually reflect VHF radio and thus transmissions are restricted to the local area (and don't interfere with transmissions thousands of kilometers away). VHF is also less affected by atmospheric noise and interference from electrical equipment than lower frequencies. Whilst it is more easily blocked by land features than HF and lower frequencies, it is less affected by buildings and other less substantial objects than UHF frequencies.
UHF is the most commonly used frequency bands for transmission of television signals. Modern mobile phones also transmit and receive within the UHF spectrum. UHF is widely used by public service agencies for two-way radio communication, usually using narrowband frequency modulation, but digital services are on the rise. Narrowband radio modems use UHF and VHF frequencies for long range data communications e.g. for supervision and control of power distribution networks and other SCADA and automation applications. There has traditionally been very little radio broadcasting in this band until recently. The Global Positioning System also uses UHF.
ITO offers its client's state of the art HF long distance communications as well as digital trunked (TETRA) radio systems in the VHF/UHF frequencies. Contact us for a solution for your companies communications needs.