These are the default HartRAO PSS values from the 
www.hartrao.ac.za/hh26m_factsfile.html webpage.
If the CALDB has no PSS value for your target, these
values will be applied.

Wavelength [cm], PSS [Jy/K/pol]
18,5.1
13,4.8
6,6.0
4.5,5.1
3.5,6.1
2.5,5.8
1.3,10.5