RF (Radio Frequency) systems relies on radio waves for data transmission. Radio frequency that RF systems operate at are between 10 kHz and 1 GHz. Radio frequencies are regulated by the country. Different kinds of radio antennas broadcast different types of radio signals. Most powerful antenna is a traditional radio tower. Other types of antennas are half-wave dipole, beam, and random length wire.
The power of RF signal is affected by transceiver and antenna power. Three categories of radio waves are spread spectrum, single frequency low, and high power.
Single frequency transceiver uses single frequency to operate at. Low-power device transmits for about 25-30 meters distance, while high-power transmitter can send signal to anything in the line of sight or even beyond horizon if the signal is reflected off the earths atmosphere. Both low- and high-power devices are able to operate at any frequency, although higher gigahertz ranges offer better throughput. Low-power transmission equipment is cheaper than high power installation. Compared to low-powered system, high powered system is having complex installation. It might require skilled technician to install and maintain. Improperly installed equipment would provide poor transmission rates and data loss. Both solutions could transmit data between 1 and 10 Mbps. resistance to EMI is low for both transmission types. Both transmission types are susceptible to eavesdropping, however high-power transmission is more vulnerable due to its extended transmission distance.
Spread spectrum is using multiple frequencies simultaneously. The direct frequency modulation and frequency hopping modulation schemes are used to achieve that.
Direct frequency modulation is splitting original data into part which are transmitted over different frequencies. In order to confuse signal interception, several spurious signals are being transmitted together with the data. Receiver is aware of which frequencies to listen to. After receiving all the data it is able to assemble multiple signals back to original data.
This system is fairly inexpensive compared to other wireless solutions. Different equipment solutions may or may not require specialized person to install it.