Suggested Radio Equipment for Community Safety

Several people have asked what our recommendations are for radios; not only amateur radio equipment, but also scanners and shortwave monitoring. Communications are a vital aspect of our every day lives. Communication will be just as important, or more so, in a disaster or emergent situation. Having reliable equipment relieves the end user of much frustration and could be a life saver.

First, a very brief discussion of radio frequency is in order for those readers who have not made any study of radio previously. Radio waves are a type of electromagnetic radiation which moves at the speed of light from the transmitting antenna. This radiation takes the form of electromagnetic waves. Higher energy waves have a higher frequency (number of waves per second) and a shorter wavelength (distance between each successive wave peak).  Lower energy waves have a lower frequency and longer wavelength. Frequency is measured in megahertz (MHz) or millions of waves per second. Different portions of the entire frequency range are grouped together and given shorthand names to aid in their discussion.

Electromagnetic wavelength

The portion of spectrum which interests us for purposes of this article runs from approximately 3 MHz up to 3,000 MHz. This range has been grouped into three sections.  High Frequency (HF) runs from 3 MHz to 30 MHz. Very High Frequency (VHF) goes from 30 MHz to 300 MHz, and Ultra High Frequency (UHF) runs from 300 MHz to 3,000 MHz.

HF is primarily used for long-range communication. HF signals are reflected from the ionosphere which allows them to propagate beyond the horizon. HF signals may take several reflections off the ionosphere and off the earth to travel great distances. This kind of atmospheric reflection is referred to as skywave propagation. VHF and UHF are considered line of sight frequencies. VHF and UHF are limited to distances not much greater than the distance to the horizons, assuming no obstructions to the line of sight. In certain atmospheric conditions, VHF signals may be reflected by the atmosphere, allowing for greater range, but this happening at UHF is exceeding rare and neither should be relied upon for communication. Most VHF/UHF signal propagation is direct wave or surface wave propagation, and reflection.

HF Skywave Propagation

 

VHF/UHF Propagation; Direct wave, Surface wave, and Ground reflected wave

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