2-WAY RADIO RANGE: HOW FAR CAN TWO-WAY RADIOS COMMUNICATE

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One of the most common questions people ask when they are in the market for a two-way radio or wireless intercom is how far do they communicate? Unfortunately asking this question is along the lines of asking, "How far is up?". There are lots of variables involved and no easy, definitive answer. A brief lesson on radio signal transmission is required to understand the whole range issue.

If you are old enough to remember when AM radio was popular you may remember listening to radio stations that were hundreds of miles away. For frequencies like these below 2 Megahertz (MHz), these signals follow the Earth's curvature because they are reflected off the atmosphere. So AM radio signals in low-noise environments can be received by radios that are way below the horizon hundreds of miles away.

The two-way radios and intercoms available for you to purchase usually fall in the frequency range of 150MHz to 900MHz (this covers our 151.7MHz channel and 448.6MHz Ogden Repeater channel). Unlike the AM radio waves, radio waves in these frequencies travel in straight lines and as a general rule cannot travel over the horizon or behind solid obstacles.
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But as in all general rules, there are exceptions to the rules. Even though these frequencies travel via "line-of-sight" paths, radio signals can travel through many non-metallic objects and be picked up through walls or other obstructions. Even though we can't see between antennas of a transmitter and receiver, this is still considered line-of-sight to the radios. Also, radio waves can be reflected, or bounce off surfaces so the straight line between radios, may not always be so straight.
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Knowing that our radio waves travel in straight lines, then to figure out their maximum range for a two way radio we have to factor in the curvature of the Earth. When you stand on Earth and press the talk button on your radio, the radio waves are going straight and they will eventually just go straight off into space once they pass the horizon. So the distance of the horizon is technically the maximum communication range for a two way radio. But you have to factor in antenna height as well.

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