"Radios, Radios, Radios"
Jim Sweitzer - January 12, 1995
Although the South Pole is environmentally pristine in almost every way, there is an unseen presence that can "pollute" in a way. I'm referring to radio waves. Radio is, of course, a form of light energy, but with waves much longer than the visible light with which we see. We use it back in CONUS for the radio and TV stations we tune into and other types of communications. Here at Pole, there are no radio or TV stations, so radio is used for communications with aircraft and between people on foot or in vehicles at the Pole. When we are in the galley for lunch or dinner, you can here personal radios squawking constantly, demanding immediate attention.
But this "pollution" is more troublesome than simply these little radios interrupting conversations. There are several experiments at Pole that use or detect radio waves of some kind. One reason they are here is because we are in a part of the world that is radio quiet. This means that normal radio and TV signals never reach us. When conditions are right you can hear a shortwave broadcast station or two, but that's it.
There are experiments here that use radio waves to probe the ionosphere of the earth. This outer layer is so named, because it is made up of atoms that have had electrons ripped off. Such atoms are called ions. The ionosphere can act like a mirror to reflect radio waves. There is one experiment here that studies how well and at what frequencies the ionosphere reflects. Another experiment bounces radio waves (sort of like radar) off of meteor trails high in the ionosphere (120 Km altitude) to study the earth's ionospheric winds at the edge of space.
Those experiments generate radio "pollution" too, just like the squawk of the personal communications radios. This can be a problem for experiments like CARA's AST/RO project. AST/RO is a radio telescope designed to detect very week, ultra-short radio waves. These waves come from atoms and molecules in space and tell us about the places in our galaxy where stars are being born. AST/RO is so sensitive to radio pollution that its radio receivers and spectrometers are in a very special building out in the dark sector. This building is shielded from radio waves by a uniform conducting skin. Even the windows have screens in addition to their regular Plexiglas surfaces. All of this is to keep radio waves from penetrating and reaching the sensitive receivers tuned to cosmic nurseries in the Milky Way. This shielding plus filters and being isolated out one kilometer from the main base help to keep the environment quiet enough for AST/RO.
After lunch today I took a while to generate some of my own radio interference. There is a radio here designed for communicating at amateur radio frequencies. Since I have a ham license, I usually try to operate this radio at least once during my visits. The station callsign here is KC4AAA. Before there were satellites, this was the only way to get voice communications out of Pole. You operate at a frequency of 14 million cycles per second with the station's radio. This frequency is far higher than normal AM broadcast radio. As a result, if the ionosphere is reflecting well, you can bounce these waves right back to CONUS. Luckily this was a day when the ionosphere decided to cooperate and the signals were strong. It's amazing to me that only 500 watts of power from the station here should do such a good job contacting another station in Chicago 9,100 miles away.
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