From the standards: Radio Frequency Sources (9kHz to 60GHz) for continuous transmissions and pulsed transmissions whose pulse duration exceed the thermal initiation time shall not exceed limits below:
However, for Group I in South Africa, there were DMR directives (ME-2-2003 signed; MS-2-2010 unsigned) that contradict IEC/SANS60079-0 standard of 6W RF transmission stipulating 500mW.
This dates back 18 years now & a lot has changed in this time. Reasons I have been offered for this 500mW in underground coal mines have been:
- Concern over spurious triggering of detonators.
- Concern of interference with collision detection systems.
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