December 05, 2002
Tactical Radio Communications, installment 6
Polarization
Radio waves have an orientation, usually vertical or horizontal. Note how external TV antennas have all their elements lined up in a flat fashion (horizontal polarization), while CB and two-way radio antennas point straight up (vertical polarization). Having the polarization different between antennas can cause significant signal loss, thus it is important to always mount antennas in the same direction (vertical for most two-way radio applications).
Antenna height
At higher frequencies (30MHz and above), the height an antenna is above the ground has a direct affect on how well it performs. High frequency radio waves are blocked by the ground and tend to travel about the same as one’s line of sight. This is the usually the main limitation on the distance one can communicate. The higher one is, the farther they can see, and the exact same principle applies to radio waves. A 1-watt portable may only work for 2-3 miles at ground level. If you put that radio on a 5,000-foot mountaintop, the range can be increased to 10-20 miles or further. A good rule of thumb is if your radio contact drops off, try moving to higher ground.
Posted by Eric Cartman at December 5, 2002 08:30 AM | TrackBack