extracted by the time convolution of the pseudo noise encoded preamble for the data message with waveform 54 with the preamble preceding the data stream this known preamble is resident in the radar 39 s signal processor and is designed to extract the message from the tag on the up link this preamble is also resident in the tag time convolution of the two waveforms the results in the extraction of the data referring to fig8 what will be seen is that to the external world the data message here illustrated at 66 has an amplitude which is much less than the amplitude of the radar spectrum with the graphs of fig8 being in the frequency domain thus the relative amplitude of the radar frequency spectrum 68 is orders of magnitude higher than that of the data message referring to fig9 in the past there has been a need to provide a variable tap convolver to match the bandwidth of the various interrogating radars or other interrogating signals thus for instance assuming an x band interrogating radar signal were to be utilized with a particular chirp rate and a particular pulse repetition interval then the variable tap convolver needed to be set for this particular interrogating waveform since there is a possibility of numerous different types of interrogating waveforms.