MMA Memo #168

Relative Sensitivities of Single and Double Sideband Receivers for the MMA

A.R. Thompson [1], A.R. Kerr [1]

April 14, 1997

Keywords: single-sideband, double-sideband

Plans for the MMA include development of sideband-separating SIS mixers,which will allow operation of the SIS receivers in a single- sideband mode (MMA Memo 151). In this memorandum we estimate the relative sensitivities of single- and double-sideband receivers for a range of conditions that roughly approximate those expected at the Chajnantor site. The single sideband system provides significantly better sensitivity for observations where only one sideband is used, as in observing a single spectral line or a group of lines that fall within one sideband. Thus even though the atmospheric component of noise at Chajnantor is relatively low, it is worthwhile terminating the unwanted sideband in a 4 K load rather than on the sky. In cases where information can be gathered in both sidebands simultaneously, as in continuum observations or in a survey of many lines, the difference in sensitivity between single- and double-sideband inputs is not so great, and depends more on the parameters assumed for the mixers and the atmosphere.

[1] NRAO

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Last modified: 09 December, 1999