Basic Qualification · B-006 Feedlines and antenna systems · B-006-010-008
Laquelle des lignes de transmission suivantes fournit la meilleure adaptation à la base d'une antenne quart d'onde à plan de sol?
- AUne ligne de transmission symétrique de 300 ohms
- BUne ligne de transmission symétrique de 75 ohms
- CUn câble coaxial de 75 ohms
- DUn câble coaxial de 50 ohms
Correct answer: D — Un câble coaxial de 50 ohms. Question tirée de la banque officielle d'ISDE.
Why
A quarter-wave ground-plane antenna naturally presents an impedance close to 50 ohms at its base, which matches perfectly with 50-ohm coaxial cable. The full explanation — and one for every question — is in Pro.
Practise this section
Feedlines and antenna systems is section B-006 of the Basic exam: Getting the signal out: antennas, feedlines, SWR, baluns, matching, and why antenna length depends on frequency.
Drill B-006 — free, no account