In telecommunication, the term k-factor has the following meanings:
1. In tropospheric radio propagation, the ratio of the effective Earth radius to the actual Earth radius.
Note: The k-factor is approximately 4/3.
2. In ionospheric radio propagation, a correction factor that (a) is applied in calculations related to curved layers, and (b) is a function of distance and the real height of ionospheric reflection.
Source: from Federal Standard 1037C and from MIL-STD-188