>it wasn't obvious to me why they needed a $250,000 network analyser, given that there's no network and no signal to analyse Radio frequency (RF) network analy

>it wasn't obvious to me why they needed a $250,000 network analyser, given that there's no network and no signal to analyse Radio frequency (RF) network analyzers are test and measurement instruments used to characterize the performance of RF and microwave components and systems. >The amplification result is rather puzzling; I wonder if the antenna was in contact with the helmet The helmet is functioning as a roughly spherical resonant cavity. Any such resonant cavity will have resonant frequencies and the signal strength inside the cavity will be stronger at certain locations and frequencies than outside the cavity. >I'd like to know how they fitted a directional antenna under the helmet, without it showing. They placed a helmet around an antenna, with the antenna inside a mannequin head, so as to measure the signal strength that would be present in the locations that would be inside the head if the helmet were to be worn by the wearer.