23 July 2007
By Chris Handy
The Daily Texan

Shortwave radio is an excellent medium for keeping tabs on global events.
Signals can be received from around the world at absolutely no cost to the
listener, with a wider range of content than most local radio programming.
Shortwave transmitters can be operated at a relatively low cost by
organizations or even individual hobbyists, lending shortwave a freedom of
expression unparalleled by mainstream media. In addition, the multilingual
and multicultural content of shortwave fosters the development of a great
diversity of perspectives. "DX'ing," or distance listening, is a rewarding
hobby with little overhead required.

Despite being more affordable and easier to access than ever before, many
people are completely unaware that shortwave exists. Technical
considerations have also given a certain stigma to shortwave as difficult to
use. The high frequency waves (3 megahertz to 30 megahertz) are too high to
be picked up on an ordinary AM radio, requiring the purchase of special
equipment. Sound quality is almost never as stable as local transmissions,
and shortwave transmissions even have a tendency to drift to neighboring
frequencies with changes in the weather.

But the close relationship between shortwave signals and the weather is the
medium's greatest feature. What we call shortwave is simply a range of
frequencies within the larger set of all electromagnetic radiation, which
includes all other types of radio, as well as visible light, X-rays and
microwaves. Signals in the shortwave range have a peculiar tendency to be
reflected by our planet's ionosphere, a layer of gases extending from 50 to
600 miles above Earth's surface. Instead of beaming directly out into space,
a shortwave signal sent from Earth at the proper frequency and angle will
reflect back toward the planet's surface, where it can be received at
another location.

By modifying the frequency and transmission angle, a shortwave transmitter
can send signals to literally any point on the planet. Because the
transmission relies on natural weather conditions rather than commercial
satellites, there is no fee to receive the transmissions. Anyone wishing to
receive a broadcast need only set up a suitable antenna and find the proper
frequency.

The same atmospheric properties that keep shortwave listening free also
prevent it from being commercially viable. Sound quality tends to be poor
and is best suited to voice-only broadcasts, like the news. Sunspots and
other cosmic events that interact with Earth's atmosphere can also interfere
with shortwave transmissions. Time of day, season, temperature, cloud cover
and other factors can all change the reception of any particular signal
quite dramatically.

Yet shortwave continues to remain popular and is in many ways growing in
popularity. A sturdy low-end receiver can be purchased for $150 or less,
allowing full reception of the entire shortwave frequency range. Newer
computer-controlled receivers make the task of finding signals much easier
by providing scanning functions and visual maps of current planetary weather
conditions. Some bold-hearted and technically inclined users even build
their own receivers.

Many DX'ers enjoy listening for the quirky eccentricities of the shortwave
spectrum, which carries a variety of unusual and often unidentifiable
transmissions. Particularly intriguing, for example, are "number station"
broadcasts, during which a voice reads out long strings of numbers, with no
explanation of their purpose and no identification of the transmitter. Some
people think these transmissions are coded instructions for international
spies. Other signals to listen for include weather satellites and ham
radios. Natural phenomena, such as the aforementioned sunspot activity, can
also be received and studied, allowing the shortwave receiver to function as
something like a low-end radio telescope.

(Handy is an Asian cultures and languages graduate student.)

http://media.www.dailytexanonline.co...-2926149.shtml