I prepared an Excel 2003 that computes BC for the mentioned methods of element mounting of 144 and 432 MHz. The little mathematics and factors behind are what I have shown in the past Dubus articles.
To use it the Excel 'macro safety' should be set to medium, thus asking every time whether an MS office application using a VBA macro should be allowed to do so or not.
This Excel runs a Visual Basic for Applications (VBA) in the background. It must be Excel 2003 with full installation of the VB options if it shall work. Importing this to Excel 2007 or 2010 won't work since Microsoft was so ingenious to change the object catalogue with almost every version of MS Office so far.
Tnx es vy73, Hartmut, DG7YBN
Download this Excel spreadsheet

insulators for the BC-excel