Question T9A07
From subelement T9 - T9A
What is a disadvantage of using a handheld VHF transceiver with a flexible antenna inside a vehicle?
Why is this correct?
The correct answer is A. The metal body of a vehicle acts as an RF shield, blocking VHF and UHF signals. Metal surfaces reflect and absorb these higher frequency signals, creating a 'signal shadow' that dramatically reduces your radio's effective range. Options B and C are incorrect because the shielding effect doesn't primarily affect antenna bandwidth or SWR characteristics—it simply blocks signal propagation through the metal structure.
Memory tip
Remember that VHF/UHF signals behave more like light—they're easily blocked by solid objects. Lower frequency HF signals can bend around obstacles better, but VHF/UHF need a clearer path. This shielding principle applies to any metal enclosure, not just vehicles.
Learn more
In practical operation, this shielding effect explains why mobile installations use external antennas mounted on the vehicle's exterior. The FCC's emission standards require efficient radiation, which can't occur when signals are trapped inside a metal cage. Professional mobile operators position antennas on magnetic mounts or permanently install them outside the passenger compartment to achieve proper frequency privileges and maintain signal integrity across their authorized bandwidth.
Think about it
Why do you think satellite communication systems often place amplifiers directly at the antenna rather than using long cable runs, especially at higher frequencies?