Ratios to dB, dB to ratios, dBm to watts, and a station budget that adds feedline loss against antenna gain. Decibels add where the plain numbers would multiply, which is the whole point of them.
Ratios to dB and back, dBm to watts, and a station budget.
Decibels turn multiplication into addition — the reason antenna gain, feedline loss and power all live on the same scale.
Gain is relative — check whether a figure is dBi (vs an isotropic) or dBd (vs a dipole); they differ by about 2.15 dB.
