Memo Review Reply Memo: 372 - An Amplitude Calibration Strategy for ALMA Moreno & Guilloteau, 2002May10 Reviewer: Larry D'Addario Date Received: 2002Aug22 Reply from: Mark Gurwell Date Received: 2002Aug22 Reply: I know I said I couldn't review the amplitude calibration memo, but I could not let Larry's email on amplitude calibration pass through without a quick comment on the need for sideband ratio calculation; he claims that the sideband ratio is unimportant for continuum observations, and that 'sideband suppression' within the correlator makes it unimportant for line work. These comments may be true at low frequencies where the atmospheric opacity is the same in each sideband, but they are definitely not true in the case where the opacity is different. Only with a knowledge of the SBR can one accurately use the measured system temperature (which is inherently a DSB operation) to get the single sideband system temperature which is the first order correction to amplitude. This situation becomes more and more important at the higher frequencies, and especially in band 8 where the window is narrow and chopped by many water lines.