Subband gain differences

There may be small gain differences of 1% in adjacent subbands. This will only cause problems when a very bright line is placed on the overlap region, ie the exact centre of a subsystem with an even number of subbands (most configurations). This effect can be seen as a shift in the baseline level by about 1% of the peak brightness temperature, resulting in a platform on the baseline, which cannot be trivially fitted by SPECX. If this is a problem, it can be fixed by (i) scaling adjacent subbands by the appropriate factor (0.99-1.02) or (ii) shifting the line away from the overlap region (to the centre of a subband). Unless extremely accurate calibration is needed, it will be possible to reduce the data in such a way that this effect is removed. In most practical cases, this is not a significant effect.