Advanced Qualification · A-007 Feedlines and matching · A-007-005-004
Sur quel type de communication VHF et UHF le décalage Doppler ("Doppler shift") devient-il significatif?
- AContact via un satellite
- BContact via un répéteur sur une colline
- CContact simplex entre portatifs en propagation à vue
- DContact avec une station terrestre mobile
Correct answer: A — Contact via un satellite. Question tirée de la banque officielle d'ISDE.
Why
Satellites orbit Earth at high speeds, creating a rapid change in distance that shifts the radio frequency you hear, much like the pitch of a passing siren. The full explanation — and one for every question — is in Pro.
Practise this section
Feedlines and matching is section A-007 of the Advanced exam: Feedlines and matching at the advanced level: transmission line theory, impedance transformation, stubs and matching networks.
Drill A-007 — free, no account