While using a 2-metre hand-held transceiver in an urban setting, you notice that moving less than one metre can severely attenuate your received signal. What is the likely cause?

In an urban setting, buildings, metal structures, and other objects reflect VHF radio waves like those on the 2-metre band. This creates multiple paths for the signal to reach your antenna, a phenomenon known as multipath propagation. Because the wavelength of a 2-metre signal is precisely 2 metres long, moving your radio just a fraction of a metre (like half a wavelength, or 1 metre) can dramatically change the phase relationship of the incoming signals. In one spot, the reflected signals might arrive in phase and combine perfectly; step slightly to the side, and they might arrive out of phase, completely cancelling each other out. This destructive interference causes severe, localized drops in signal strength often called 'multipath fading' or 'picket fencing'. Distractors like Faraday cages or passing vehicles absorbing signals do not explain the extreme sensitivity to moving such a short distance.