Propagation @ DXing Info

Just about everyone remembers the very first distant shortwave station they ever heard. It seemed so easy at first, to travel great distances by radio. But later we find out that shortwave listening is much different than listening to our local stations because nothing stays constant. Signal strengths may vary from day to day, we discover some bands of frequencies work better at different times of the day or night, and some of our favorite stations switch frequencies at different times of the day or at different seasons of the year. Also, some stations can sound very distorted and hard to understand.

Sky Wave, Groundwave and Ionosphere

First, we need to understand the parts of a radio wave. When we talk of radio waves leaving the transmitting antenna and traveling through space, we will refer to the groundwave and the skywave. The GROUNDWAVE is the part of the signal that travels along the ground, and at low-enough frequencies will even curve over the horizon. The low frequency stations will have a groundwave that can go great distances, while higher frequency stations will have shorter ground waves, until eventually at very high frequencies the groundwave is practically limited to line-of-sight  

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Understanding

Understanding and Using Propagation Knowledge

In planning what frequencies are best to use for communications with a specific part of the world, we have to know propagation. Many frequencies depend on a total path of darkness. A solar event will make some frequencies temporarily poor. A high frequency opening to a seldom-heard part of the world may appear without warning. Keeping up with propagation conditions will help improve radio listening by being efficient.

Propagation forecasts are available from some observatories and governments on a regular basis. Forecasts are made by keeping a regular count of sunspot numbers. Observations of solar flares result in predictions of when and how bad it may affect radio conditions. And since the sun rotates on a regular cycle, a bothersome sunspot can be predicted to come around again 27 days later.  

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Solar Guide

One of the handiest (and cheapest) methods to better understand the current state of shortwave radio propagation conditions is by monitoring the Geophysical Alert Broadcasts made at 18 minutes past each hour over the U. S. National Institute of Standards and Technology radio station WWV in Ft. Collins, Colorado and at 45 minutes past each hour via WWHV on the island of Kauai in Hawaii WWV broadcasts continuously on shortwave frequencies of 2.5, 5, 10, 15, and 20 MHz and WWVH broadcasts on 2.5, 5, 10 and 15 MHz. Their signals are audible throughout North America and the Pacific Region and often the rest of the world, depending upon radio propagation conditions.

About the Author Carl Mann:

Carl Mann has been listening to short-wave since 1956. He began after noticing the distant stations audible between the locals on the AM band. This started his armchair travels that most DXers embark upon to the four corners of the world. Thousands of loggings, tapings, and hundreds of QSL's later, this accumulated experience is briefly summarized in "DX TIPS FOR BEGINNERS" to ...Read More>>
This book may also be purchased separately from Universal Radio only US$1.95. Site: http://www.universal-radio.com/catalog/books/0027.html