CONFIRMATION STEP 1: RECEPTION CONDITION SYMPTOM (EXAMPLE) [RADIO]

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Symptom | Antenna signal condition | Source
--- | --- | ---
Only a buzzing sound from the speakers | • There is no broadcasting wave. • Signals from antenna to audio unit are not transmitted. | • Electric noise caused by the operation of internal circuit from audio unit itself • Atmosphere noise
A buzzing or crunching sound and normal sound produced at the same time from the speakers | • Though signals are transmitted from antenna to audio unit, electric noise from other sources is larger. | • Electrical noise caused by operation of electrical component on vehicle • Electrical noise from high tension wire, transformer substation (factory), electrical feeder line (street car), or motorcycle.
A thumping sound and normal sound produced at the same time from the speakers (FM only) | • Noise occurs due to radio wave environment at specific places (e.g. in valleys between buildings). Noise varies when own vehicle or surrounding vehicles moves. (FM only) | • Interference between direct and reflected waves of FM signals causes noise (Multipass noise).