In amateur radio, QRP operation refers to transmitting at reduced power while attempting to maximize one's effective range. QRP operation is a specialized pursuit within the hobby that was first popularized in the early 1920s. QRP operators generally limit their transmitted RF output power to 5 Watts or less regardless of mode be it CW operation or SSB operation. Reliable two-way communication at such low power levels can be challenging due to changing radio propagation and the difficulty of receiving the relatively weak transmitted signals. QRP enthusiasts may employ optimized antenna systems, enhanced operating skills, and a variety of special modes, in order to maximize their ability to make and maintain radio contact. Since the late 1960s, commercial transceivers specially designed for QRP operation have evolved from vacuum tube to solid state technology. A number of organizations dedicated to QRP operation exist, and aficionados participate in various contests designed to test their skill in making long-distance contacts at low power levels. Etymology The term "QRP" derives from the standard Q code used in radio communication, where QRP is used to request "Reduce power" and QRP? is used to ask "Should I reduce power?". Philosophy Most amateur transceivers are capable of transmitting approximately 100 watts, but in some parts of the world, such as the U.S., amateurs can transmit up to 1,500 watts. QRP enthusiasts contend that this practice is rarely necessary, and doing so wastes power, increases the likelihood of causing interference to nearby televisions, radios, and telephones and, for United States' amateurs, is contrary to FCC Part 97 rule, which states that one must use "the minimum power necessary to carry out the desired communications". QRP can also be used for emergency communications during disaster recovery, when frugal use of available battery power and generator fuel is crucial. Practice The practice of operating with low power was popularized as early as 1924, with a variety of reports, editorials and articles published in U.S. amateur radio magazines and journals that encouraged amateurs to lower power output, both for purposes of experimentation, and for improving operating conditions by reducing interference. There is not complete agreement on what constitutes QRP power. Most amateur organizations agree that for CW, AM, FM, and data modes, the transmitter output power should be 5 watts (or less). The maximum output power for SSB (single sideband) is not always agreed upon. Some believe that the power should