This is a consequence of Lorentz reciprocity. For an antenna element  not connected to anything (open circuited) one can write . But for an element  which is short circuited, a current is generated across that short but no voltage is allowed, so the corresponding . This is the case, for instance, with the so-called parasitic elements of a Yagi-Uda antenna where the solid rod can be viewed as a dipole antenna shorted across its feedpoint. Parasitic elements are unpowered elements that absorb and reradiate RF energy according to the induced current calculated using such a system of equations. COUNT 5
QSN1 a antenna element not connected to anything is circuited how? ANS1 open circuited QSN2 When is the element not allowed voltage? ANS2 short circuited QSN3 What element absorbs and reradiate RF-energy? ANS3 Parasitic QSN4 What antenna can the solid rod be viewed as a dipole antenna? ANS4 Yagi-Uda QSN5 Where can this solid rod be viewed? ANS5 feedpoint