'QRP' is a
morse code symbol meaning 'reduce your
transmitter power'. In amateur radio, it denotes radio
communication with low transmitter power. While no formal definition of 'low power' exists, many amateur radio organizations consider QRP to be output power below 5
watts.
Antenna gain is not assessed.
Shortwave contacts over distances as much as 1000 miles can be made with 1 watt and a wire antenna, when interference is low. However, making DX contacts with low power is a challenge requiring a high level of operating skill, good receiver design and thoughtful placement and construction of antennas.
Finally, in an age of $5000 transceivers, QRP allows for the opportunity to make contacts using low-cost or even home-made equipment; home-brewers are common in this subtype of amateur radio.