Method is provided for increasing the productivity of gas wells producing from reservoirs where retrograde condensation occurs around the wells. The apparatus for transmitting a message in a portable terminal comprises a message generation unit for generating a message including contents corresponding to at least two recipients and for selectively selecting an intended user for the respective content, and a controller for controlling to transmit the message to the at least two recipients. The tube has a non-circular cross-sectional shape along the length of the tube. A sign data is encoded into the digital data through a linear combination operation to obtain an encoded digital data, wherein the size of the digital data is not changed after the encoding process.