For synchronization purposes, a transmitter (TX) multiplexes a pilot carrier
with carriers whereon data elements (DATA) are modulated, and transmits the pilot
carrier together with the modulated carriers to a receiver (RX). The immunity of
the pilot carrier for interferers, such as radio amateur signals, is improved by
modulating the pilot carrier with a non-constant signal, for instance a random
signal, an alternating signal or even scrambled data elements (DATA), before transmission
thereof. Since demodulation of the pilot carrier in the receiver (RX) and averaging
successive demodulated pilot carriers reduces the effect of the interference induced
on the non-constantly modulated pilot carrier, the degradation of the synchronization
between transmitter (TX and receiver (RX) is reduced significantly.
