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RF is a widely accepted acronym for Radio Frequency . RF refers to the communications capability of modulating a signal over common airwaves. Radio Frequencies are those that are located in the band above 20Khz (human ear can receive 20hz-20Khz), thus requiring some form of receiver (other than the human ear) to translate the signal into something usable. For a frequency to be considered RF, it is said to be at least beyond the frequency range of the human hear. RF signals can be easily transmitted through the air using transmitters and receivers, as well as passed through wires. The most common method of transmitting RF over a wire is using Coaxial cable (coax). Coax cable uses solder-on or crimp-on connectors in a variety of sizes. Typical CATV applications use an F-style connector. Different quality exists on the connectors as well. Avoid the "screw-on" type, and opt for the crimp-type connectors. A suitable coaxial cable crimper is needed to perform this without fail. Modulation Explained. Modulation is the process of combining an electronic signal (desired information) to a carrier signal (for transport). Most common forms of modulation use an alternating current carrier and use various forms of modulation techniques. AM (amplitude modulation), FM (frequency modulation) PM (phase modulation), and PCM (pulse code modulation) are the most common in today's RF environment. RF Frequency ranges:
Noise. For the discussion of RF, we'll consider anything other than the intended communications signal that operates in the same frequency range to be considered noise. For example, when traveling between cities, metro FM broadcasts get weaker, the farther from the transmitter you travel. If your car radio is tuned to 99.7Mhz (Memphis), and you're traveling east towards Nashville, and the signal strength of the Memphis station (the one you want to listen to) is exceeded by another station at 99.7Mhz (in Nashville), guess what? You just changed stations just due to your proximity to each transmitter, and their relative broadcast signal strength. If the station in Nashville did not exist at the same frequency, you would have listened to the Memphis station until you had traveled far enough for the signal strength to be just too low to receive. In this example, however, a competing signal at the same frequency created noise (considering your desire to listen to the Memphis station as long as possible). |
RF
