Basic Qualification · B-005 Basic electronics and theory · B-005-008-005
Si un signal émis avec 150 watts de puissance est reçu à un niveau de "20 dB au-dessus de S9" au S-mètre, quelle sera la nouvelle lecture si la puissance est réduite à 15 watts?
- AS9 plus 5 dB
- BS9 plus 3 dB
- CS9
- DS9 plus 10 dB
Correct answer: D — S9 plus 10 dB. Question tirée de la banque officielle d'ISDE.
Why
Reducing power from 150 watts to 15 watts cuts the signal strength by a factor of ten, which equals a 10 decibel drop. The full explanation — and one for every question — is in Pro.
Practise this section
Basic electronics and theory is section B-005 of the Basic exam: The theory: Ohm's law, power, series and parallel circuits, AC and DC, frequency and wavelength, decibels, and the metric prefixes the exam leans on.
Drill B-005 — free, no account