subject: Cb Radio And Long Range Listening [print this page] Although CB radio is designed for short range use it is sometimespossible to listen in on some interesting transmissions, some from the other side of the globe. This 'DX listening' has become very popular with radio enthusiasts of all kinds, including those who operate CB radio.
There is, however, considerable variation in the ability to hear over long distances. While this was first thought to be due to weather conditions, we now know that the major influence on the reception of distant radio signals is something much more exciting; the sun spot cycle.
Sunspots are plumes of radiation which turn the upper atmosphere (ionosphere) into an electrically charged plasma which reflects radio signals. They are, in earthly terms, unbelievably violent and the resulting solar flares can travel at a significant portion of the speed of light, reaching the Earth in only fifteen minutes. The most spectacular example in recent times was in September of 1859. The result was a geomagnetic storm of huge proportions; telegraphs were interrupted, some operators experienced electrical shocks and in other offices equipment caught fire. Aurorae were seen all over the Earth and far further south than normal, reading the Caribbean and Texas. Gold Miners in the Rocky mountains were so confused by the light in ther night sky that they started to make breakfast, believing it was morning. Although the 1859 occurrence, known as the Carrington Event, was the largest geomagnetic storm in recorded history, ice cores have shown that similar storms happen regularly at intervals of around 500 years.
A more recent geomagnetic storm, again caused by solar activity in March of 1989, while far slower and of lesser intensity caused enough interference to jam some radio transmissions and once again there were very intense aurorae appearing as far South as Texas. Many of the satellites in Earth orbit lost control for a period of several hours and some feared that a nuclear attack was imminent.In Quebec the variations in the Earths magnetic field tripped circuit breakers resulting in a loss of power to the Quebec hydro area. The power loss lasted for more than 8 hours, the inhabitants of Montreal awoke to a cold world, their night-time temperature was only 19 degrees. Later the same year another similar storm affected microchips and brought Toronto's stock market to a stand still.
When a radio broadcasts, some of the signals travel outwards and upwards. Although space sounds far away to us, the upper atmosphere begins at 50km, approximately 30 miles. When there is a great deal of solar activity the solar wind bombards the Earth with charged particles, these have enough energy to strip the electrons from their atoms and send them spinning by themselves. Instead of stable, electrically neutral atoms of gas, the upper atmosphere becomes filled with charged particles and this is what reflects radio signals back down to the ground. Depending on the angle of reflection, the signal can travel hundreds or even thousands of miles from it source and can bounce more than once, making it's journey even longer. The process is affected by temperature as well as solar activity, so in addition to the eleven year solar cycle there is an annual cycle with DXing being far more common in winter, and a daily cycle where distant radio signals are usually clearest around sunrise and sunset.
Talking over 150 miles in distance is illegal for user of CB radio, but don't let this spoil your fun. Listening to distant signals is still a great way to keep in touch, and invaluable in emergencies.
