Discussion
A short whip antenna on a vehicle performs poorly at 30 MHz but acceptably at 150 MHz with no change to the hardware.
What is the principal reason?
Answer: C
A one metre whip is a hundredth of a wavelength at 30 MHz and a half wavelength at 150, so its radiation resistance rises from a fraction of an ohm to tens of ohms and its efficiency with it. The ground plane and noise arguments have some force but are secondary, and the transmitter is unchanged. This single relation explains most of why antenna practice differs so sharply between the high frequency and very high frequency bands.
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