In a burst of brilliance in 1864, James Maxwell theorized that electromagnetic wave (radio and light) could travel through free space without the mythical ether or quintessence.
A few years later, Heinric Rudolf Hertz (the unit of cycles per second is named for him) was able to prove electromagnetic wave could propagate through free space, which confirmed Maxwell’s theory of electromagnetism.
In fact, for many years, radio waves were called Hertzian waves.
Radio is derived from the word radiation, or to radiate. You see, the electromagnetic spectrum contains radio waves, microwave, infrared light, visible light, ultraviolet light, X-rays and Gamma rays. These are all forms of electromagnetic radiation. Waldo Warren coined the word “radio,” and it was adopted by the United States Navy in 1912.
These waves travel in interesting ways across our sky, in outer space and even into the earth and oceans.
Today, the majority of radio-wave devices operate by line of sight, which means the radio waves propagate in a straight line between the transmitter and receiver, such as broadcast TV, cell phones, walkie-talkies, wireless networks, telecommunications microwave links and even satellites. Other radio frequencies, like your AM (amplitude modulation) radio band, can bend over obstacles like hills and journey well beyond the horizon. Your FM (frequency modulation) radio band tends to be more line of sight due to its shorter wave length.
Much lower frequencies can penetrate through water and earth. Communications with submerged submarines or workers in mines use very long wavelengths. The Navy’s E-6 Mercury aircraft tow a 5-mile-long antenna in flight to communicate with submarines, a very long wavelength indeed!
Shortwave and other, higher frequencies can travel across oceans and continents as they skip or refract off an abundant layer of electrons and ionized atoms called the ionosphere, which can stretch from 30 miles above the earth to the edge of space at 600 miles. Some radio stations use shortwave to broadcast internationally. This method of broadcasting is dependent upon the upper atmosphere and is most reliable during winter’s long nights.
Wouldn’t you know it, this is one of the frequency bands used by amateur radio operators.
Since the early 1900s, no other group has made a greater contribution to radio communications than our treasured amateur or HAM radio operators. Even though they are licensed by the Federal Communications Commission (FCC), they are called amateur radio operators because the FCC has set aside certain non-commercial radio frequencies for their utilization. Consequently, they are not allowed to accept any payment for their services.
They are just as innovative today as they were 100 years ago. One local group, the Cal Poly Amateur Radio Club, is primarily made of up of electrical engineering students and faculty at Cal Poly. Amateur radio operators have a distinguished history of public service as well as emergency communications. Tom Tengdin is the President of San Luis Obispo County Emergency Communications Council (SLOECC), a HAM radio operator (WB9VXY) and a Senior Telecom Specialist with PG&E. He told me that their motto is “When all else fails, ham radio.”
SLOECC is on call through the San Luis Obispo County Office of Emergency Services for situations that require alternate or additional communications. When severe weather, floods, earthquakes or wildfires occur, it can cause power outages or damage communications equipment, like cell-phone towers. When conditions like this arise, amateur radio emergency teams spring into action and relay “health and welfare” information and support first responders and government agencies with their radio equipment when other communications channels are inaccessible.
Every week, more than 100 Hams in San Luis Obispo and southern Monterey County, including the Estero Radio Club, check in over the air. Tengdin told me that effective radio communications are something that you have to practice regularly to stay effective. SLOECC meet once a month and visitors are welcome.
For more information, please visit their website at sloecc.org.
Last month, PG&E donated radio equipment that will replace the 20 plus-year-old radios that SLOECC currently use, which will improve their communications speed and accuracy.