almost always vertically polarized since 2-meter antennas on cars are usually vertically polarized. Matching polarization allows for maximum signal coupling which equates to stronger signals in both directions. Simple radios for FM repeater operation have become plentiful and inexpensive in recent years. Communications beyond 50 miles While the 2 meter band is best known as a local band using the FM mode, there are many opportunities for long distance (DX) communications using other modes. A well-placed antenna and high-power equipment can achieve distances of up to a few hundred miles, and fortuitous propagation conditions called "signal enhancements" can on occasion reach across oceans. The typical 2 meter station using CW (Morse code) or SSB (single side band) modes consists of a radio driving a power amplifier generating about 200–500 Watts of RF power. This extra power is usually fed to a multi-element, compound antenna, usually a Yagi-Uda or Yagi, which can beam most of the signal power towards the intended receiving station. "Beam antennas" provide substantial increase in signal directivity over ordinary dipole or vertical antennas. Antennas used for distance work are usually horizontally polarized instead of the vertical polarization customarily used for local contacts. Stations that have antennas located in relatively high locations with views (from the antenna) clear to the horizon have a big advantage over other stations. Such stations are able to communicate consistently. It is usual for them to be heard at distances far beyond line of sight on a daily basis without help from signal enhancements. Signal enhancements are unusual circumstances in the atmosphere and ionosphere that bend the signal path into an arc that better follows the curve of the Earth, instead of the radio waves traveling in the usual straight line off into space. The best known of these are: tropospheric ducting sporadic E meteor scatter These and other well-known forms of VHF signal enhancement that allow trans-oceanic and trans-continental contacts on 2 meters are described in the subsections that follow within this section. With the exception of sporadic E, directional antennas such as Yagis or log periodic antennas are almost essential to take advantage of signal enhancements. When a well-equipped station with its antenna well-located “high and in the clear” is operating during a signal enhancement, astonishing distances can be bridged, momentarily approaching what is regularly possible on shortwave and mediumwave. Tropospheric ducting Occasionally, signal bending in the atmosphere's troposphere known as