A transmitter for sending signals over wireless channels and a method of
sending signals over wireless channels are described. The transmitter and
the method are used to determine a transfer characteristic of an
amplifier (8) in the transmitter. Symbols in the OFDM signals to be
transmitted are multiplied by test signals at predefined points in time
to compare the OFDM symbol, which has been multiplied by the test signal,
upstream and downstream from the amplifier to determine the transfer
characteristic of the amplifier (8). This transfer characteristic of the
amplifier (8) is used by a predistorter (4) to predistort the signals
according to this transfer characteristic. The test signal, which is
generated by a signal generator (13), is input into a symbol of the fast
information channel, the test signal having an amplitude which drives the
multiplied symbol into the saturation range of the amplifier (8) with
regard to its amplitude.