Friday, March 16, 2012

Long Range CB Radio Listening. - Autos - Trucks

CB radio works over a short distance to allow many people to use it without interfering. Radio signals travel in line of sight. That means that the curve of the earth will limit distance, since the signals will just go into space. Despite this, interesting transmissions can be heard from the other side of the globe and points in between. This 'DX listening', ('DX' meaning distance), has become popular with radio users.

The ability to hear over long distances varies a lot from one minute to the next. Weather conditions were believed to be a factor, but weather can only lessen, not increase, the propagation of the signal. The real cause of DX signals is the ionosphere of the earth. Under conditions of a strongly charged ionosphere, radio waves will bounce instead of passing through. The charging of the ionosphere is credited to something much farther away. Our SUN.

The sunspots are areas of higher radiation. That radiation travels through space to reach Earth and causes the ionosphere to become an electrically charged plasma which reflects radio signals. Sunspots are known to occur in cycles. Sunspots are solar storms that are incredibly violent. Radiation of the resulting flares travels at nearly the speed of light. On average, light from the sun reaches us in about eight and one half minutes. Solar flare radiation reaches the Earth in about fifteen minutes. In 1859, a sunspot geomagnetic storm disrupted telegraphs and produced aurora borealis over most of the earth's surface. Similar geomagnetic storms seem to be on a 500 year cycle.

In 1989, a geomagnetic storm, caused enough interference to block satellite and radio signals and caused a loss of electricity for 9 hours in the Province of Quebec in Canada. A similar storm caused the Toronto Stock Market to stop operations.

Space, the final frontier! But it is a lot closer than you think. The ionosphere is only about 30 miles away. Radio signals travel outwards in all directions, including up. Solar radiation floods the ionosphere with particle radiation. The energy from these particles colliding with the atoms of air strips the electrons from them and creates ions. Radio signal can bounce on a layer of ions, and be received much farther away than normal. Reflection angles of less than 45 degrees give better bounces. Or, the longer bounce may be better. Air temperature affects the strength of the signal. Cold weather, or dryer air is better. Winter gives more DXing activity. Also better is the night, with peaks after sunset and before sunrise.

Linear amplifiers are illegal to keep you from talking over long distances. You may listen all you want. Have fun, keep a log, identify languages and remember that this, although unreliable, could be useful in an emergency.