Human body effects - 3 slides copyright Radiowave Ltd
At VHF (184MHz for example), the human body can have a significant effect. Here a person starts at the transmit antenna, which is an electrically small vertically polarised slot antenna used for remote metering from a water -pit. In this measurement the transmit antenna is mounted 1m above ground. The person then walks away from this antenna toward the receive antenna which is more than 30m away (well into the far-field region) and at 3m height agl. On the left graph more than 14dB attenuation can be seen to result from interposing an adult directly between the Tx and Rx antennas. In this particular measurement there is a +2.5dB enhancement when standing close to the transmit antenna and then a null at about 60 cm from it. The normal level for direct propagation appears at the 9dB line as the person moves further away and interaction ceases to be significant.