Foundation Radio Amateur Licence - BDARS Online Syllabus
Radio propagation basics
Recall that radio waves travel in straight lines, unless diffracted or reflected.
Recall that radio waves get weaker as they spread out.
Recall that at v.h.f. and u.h.f. hills cause “shadows” and that waves get weaker in penetrating buildings but glass windows are more transparent to radio waves.
Recall that the range achieved at v.h.f./u.h.f. is dependent on antenna height and a clear path and transmitter power. Understand that higher antennas are preferable to higher power, as they improve both transmit and receive performance. Recall that outdoor antennas will perform better than indoor antennas.
Recall that, at v.h.f./u.h.f., range decreases as frequency increases and that in general, v.h.f./u.h.f. waves have a range not much beyond “line of sight”.
Ionosphere basics
Recall that the ionosphere comprises layers of ‘conductive gases at heights between 70 and 400km above the earth.
Recall that on h.f. almost all communication relies on the waves being reflected by the ionosphere.
Recall that h.f. can provide world-wide propagation depending on how well the ionosphere bends the waves back to the earth.
Recall that this varies with frequency, time of day and season.