(1) there is agreement within 10 - 15 between the rms-values () derived from the radiometric measurements and the finite element calculations (see Fig. 1). This accuracy is set by the radiometric measurements and the atmospheric correction, rather than by the accuracy of the FE structural calculations.

(2) Figure 3 indicates that the on-axis gain-elevation
dependence
*G _{0}*(,

(3) for any wavelength in the range 0.8 mm 3 mm, the
**on-axis** gain-elevation dependence *G _{0}* is obtained from Eq. (3)
using the radio-effective rms-values

The homology calculations were originally made by ARGE KRUPP (now VERTEX) and MAN, Germany, and later repeated by P. Raffin (formerly at IRAM) and M. Bremer (IRAM). We profitted from many discussions with our colleagues in the effort to measure a reliable gain-elevation curve. We thank the referee, Mr. J. Baars, for his comments and his Occam razor.

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