Basic Qualification · B-006 Feedlines and antenna systems · B-006-010-002
Si vous construisez une antenne verticale quart d'onde syntonisée à 21,125 MHz, quelle en sera la longueur approximative?
- A3,55 mètres
- B7,10 mètres
- C6,77 mètres
- D3,37 mètres
Correct answer: D — 3,37 mètres. Question tirée de la banque officielle d'ISDE.
Why
A quarter-wavelength antenna for 21.125 MHz is roughly 3.37 metres because radio waves travel at the speed of light, and dividing that speed by the frequency gives the full wavelength, which you then split into four parts. 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