Radio frequency signals can present a hazard to humans in two ways either by contact or non contact means .
The first is simply an electric shock hazard if the potential is great enough , the RF energy tends to travel along the nerves not over the surface of the body as with low frequency ( 50Hz ) or DC , the second route is through exposure to the electric ( and magnetic ) fields from an aerial where the power density exceeds the internationally defined limits ( a web search will produce the relative information on the current limitations ) .
An aerial may be tested using low power from an instument & be perfectly safe however the same aerial becomes a safety hazard if the aerial is attached to a power amplifier .
Similarily the amplifier maybe perfectly safe when using a resistive load to dissipate the RF energy it produces , it only becomes a hazard when connected to an aerial or if it's covers are removed , if it is designed to produce above 1 watt of RF energy then the amplifier should be enclosed in a metal case , transmission lines used at higher frequencies on PCB's ARE NOT PERFECT they DO leak RF energy in addition to being a potential shock hazard .
You can either calculate the safe distance from equipment / aerials from first principles or use on of the " Online " RF safety calculators available on the internet Links these give both " Controlled & Uncontrolled " distances , they need to be locally displayed by experiments .
Jewellery can be a hazard when working with high power RF signals for instance a ring on the finger can act as a single turn winding of a transformer this could cause damage to the wearer either by an RF burn from it's surface or more likely a thermal burn from the energy circulating in the ring .
Where a risk assessment determines that hazards exist , then all the relevant control measures must be put in place to control the risk BEFORE the experiment takes place , this risk assessment MUST be signed off by the student's supervisor , in the case of Post Graduate students this risk assessment forms part of their thesis which the University requires under it's rules & regulations .
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this page last updated 29/11/09