Start here: Reciprocity means a passive linear antenna has the same directional and polarization properties in transmission and reception under equivalent conditions.
Why this changes a real station
It lets engineers use receive patterns to understand transmit patterns, but does not make transmitter power, receiver noise, nonlinear components, or active networks reciprocal.
What it looks like in practice
If a vertical hears poorly in one direction because of its pattern, adding transmitter power does not reshape that null.
What to do next
Apply reciprocity to the antenna boundary only, and keep active amplifiers, tuners with state changes, and site noise outside the claim.
Evidence boundary
Keep frequency, reference plane, antenna geometry, losses, measurement method, and safety conditions attached to the conclusion. A match, a DC check, or one field symptom does not prove efficiency or identify the complete RF path.
