Radio Frequency is Over 100 Years Old
While it may seem hard to believe, radio signal technology has been around for over a century now. By the time the Twentieth Century had started, Alexander Popov and Sir Oliver Lodge, two budding electrical engineers, were paving the way for radio. In December 1901, Guglielmo Marconi had developed a wireless transmitter and receiver. He used these tools in a famous experiment where he successfully transmitted a morse code message through radio signal from Cornwall, England, to St. John’s, Canada.
What is RF?
Today, radio frequency is so synonymous with wireless signals that the terms are used almost interchangeably, with radio frequencies describing everything from AM bands between 535 to 1605 kHz to Local Area Networks that top out at about 2.4 GHz. Traditionally, however frequencies defined as radio signals only ranged from a few kHz to roughly 1 GHz. Although, if you include microwave frequencies in radio, this range could be extended all the way to 300 GHz.
Different Frequencies are Used for Different Applications
In modern times, the use of radio is highly regulated and controlled. So much so, that specific frequencies of radio signals are used for very specific applications. For instance distress signals or telegraphs are set to only be on frequencies between 490 and 510 kHz.
Different frequencies are used for police scanners, amateur radio, cellular phones, global positioning systems or GPS, LANs and wireless internet, and even microwave ovens. The most basic and necessary applications usually are conducted on the lower frequencies, whereas more private and specific applications will occur on very high frequencies.
Why Operate on a Higher Frequency?
As you know, the frequency spectrum is fragmented and dense with allocated uses for each specific frequency. This is one of the reasons that applications keep being pushed into higher and higher radio frequencies. As new applications are discovered or intended, higher frequencies are used to accommodate them. Each frequency has different advantage and disadvantages regarding signal strength and propagation efficiency as well as interference and noise.
Frequency Shifting and Mixing
Often special technologies are need to receive and make sense of radio signals. For instance, the human voice exists on one particular radio frequency, however cellular phones operate on a different one. In order to make the human voice sound natural and normal through a cellular phone, the voice signal needs to be mixed or shifted in order to match the frequency that the phone operates on. Typically, a device called an RF downconverter is used to shift frequencies so they can be received and made sense of by radio technicians.