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A commonly asked question by folks new to the radio community is "How far will it go?". The answer is "that it depends.....".The direct "line of sight" range between two radio stations "depends" on the antenna system. Because of the curvature of the earth and multipath (echos & reflections), the higher the antennas are located above the ground (AGL) the better. For instance, a 32 mile range over "flat" terrain at a frequency of 900 MHz, the antennas must be 250 feet or more AGL (at each end) for the best performance; for 20 miles, at least 146 feet; for 10 miles, a minimum of 83 feet. This, again, is for rural and "flat ground" (the Bonneville salt flats). In urban areas, the effective range will be less, perhaps by as much as one half because of "echoes" and obstructions. Another "depends" is space attenuation (and wavelength). Radio signals loose about 22 dB of strength at one wavelength from the antenna and 6 dB with each doubling of the distance (inverse square law). If the wavelength of the signal is increased, the per mile attenuation (loss) will be reduced and if the wavelength is decreased, the signals will be increased, following the 6 dB rule. Example: at a wavelength of two meters (150 MHz) the loss for the first mile is about -80 dB, at 70 cm (450 MHz) it is approximately -90 dB and at 33 cm (900 MHz) around -96 dB. For a given effective radiated power (ERP) and other equal factors, a stronger signal will be received at a distance of one mile on 150 MHz than 450 MHz. Other "depends" include the types of antennas used, the cable feeding
the antenna, ground conductivity, atmospheric attenuation, etc. The quality
of receive and transmitting equipment, as
There are many claims of phenomenal range by manufacturers of all types
of radio gear. When exaggerated distances are achieved, there is usually
a catch like: "Yes, but the stations are on
No matter what the advertising claim, the maximum distance "depends" on many factors. No amount of marketing hyperbole can change that!
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