What Does the Value -147.55 in the VRTS Shipping Examples Correspond to?

Updated Jun 4, 2021

Issue Details

In several shipping examples for the NI Vehicular Radar Test System (NI-VRTS), there is a constant with the value -147.55 used in calculations. What is this constant and where does it come from?


This constant is part of the calculation for Free Space Path Loss, the relative power loss expected for an RF signal traveling through free space. It can be expressed as a function of Frequency and Distance; when doing so, and using hertz and meters for units of frequency "f" and distance "d", the equation can be written thusly:

If performing these calculations with other units, the constant should change accordingly.