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Syllabus Sections:-

Working with RF

8D1   51  Recall that the International Commission for Non Ionising Radiation Protection (ICNIRP) produces guidance for exposure to Radio Frequency fields.

The ICNIRP (www.icnirp.org) has guides on just how close you may stand to an antenna with a specific wattage being radiated (ERP), these guides can be obtained from Public Health England. This information is vital  when setting up say a field day or just working out the correct parameters for your own shack set up, as you must follow the guidelines for ERP exposure.

8D1  51 continued Understand it is not advisable to exceed the recommended safe exposure levels and that this is particularly applicable at location open to the public

Please check for current advisable limits for exposure, but as of May 2021 the level set for UK EMF exposure is 28V/m ,this needs to be used when setting up any field day when the public may be visiting and there may be a need for some form of physical barrier. The barrier  will prevent people getting too close to a radiating antenna and prevent accidents with any falling masts as a bonus !  Use the safe exposure rules as a general "must do" when using ham radio equipment both in the shack and out and about.


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Lightning

8E1  51  Recall that thunderstorms carry heavy static charges.

Your radio receiver whilst being selective cannot discern between a radio signal from a distant transmitter and the static build up from a thunderstorm. Cracks and pops can often be heard with other signals.
Consider these :-
•    the cracks and pops can be very loud relative to the weak station audio and if you are wearing head phones damage to hearing can be a real possibility
•    the sound of the static must alert you to the possibility of a near by lightning strike
•    static charges are looking for a route to earth and that could be via your antenna feeder, rig, earth line or even a tower if you have one.

8E1  51 continued Understand that the static charge from thunderclouds can ionise the air to form a low resistance path to ground, enabling a very high current to flow as a lightning strike.

The static charge from thunderclouds can ionise the air to form a low resistance path to ground, enabling a very high current to flow as a lightning strike. This current can be many thousands of amps at high voltages so you have a double whammy with which to contend.

8E1  51 continued Understand the risks to human life, domestic property and electronic equipment associated with a direct strike and/or the build up of static charges.

Thunderstorms can destroy Ham radio electronic equipment via static discharge and the huge magnetic fields generated by it, they also can cause death  via arching from your equipment to you in the event of a direct strike.
Domestic property can be completely destroyed by a direct strike.

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8E1  51 continued  Understand that there is little that can be done to protect an amateur station from a direct lightning strike, but that good static discharge systems can prevent dangerous static charges building up on antenna systems during thunderstorms.

There is no real protection from a direct lightning strike
•    so there are real risks to human life especially if out doors on damp ground as the whole area can become "live",
•    domestic property can be literally blown apart by a direct hit
•    electronic equipment can be totally destroyed beyond recognition

8E1  51 continued   Understand that disconnecting antenna feeders from radio equipment also reduces the risks.

Some degree of protection can be gained and can reduce the risks by :- 
•    having a good static discharge systems connected to your station, however this can be very expensive but it can prevent dangerous static charges building up on antenna systems during thunderstorms
•    disconnecting antenna feeders from radio equipment
•    provide an earth leakage route for the antennas to ground potential

Keep safe think about protecting your station



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