Advanced Qualification · A-003 Measurements · A-003-002-005
Comment calcule-t-on la puissance en crête de modulation ("PEP") si un oscilloscope est utilisé pour mesurer la tension crête à la charge fictive d'un émetteur (PCM = puissance en crête de modulation, VCM = voltage en crête de modulation, Vc = voltage de crête, RC = résistance de charge)?
- APCM = [(0,707 VCM)(0,707 VCM)] / RC
- BPCM = [(Vc)(Vc)] / (RC)
- CPCM = (Vc)(Vc)(RC)
- DPCM = [(1,414 VCM)(1,414 VCM)] / RC
Correct answer: A — PCM = [(0,707 VCM)(0,707 VCM)] / RC. Question tirée de la banque officielle d'ISDE.
Why
The formula uses 0.707 because that number converts a peak voltage into an effective heating value, known as RMS, which is what power calculations require for a resistive load. The full explanation — and one for every question — is in Pro.
Practise this section
Measurements is section A-003 of the Advanced exam: Measurements: meters, oscilloscopes, counters, signal generators, and what a reading actually tells you.
Drill A-003 — free, no account