Radio Safety

Question 1

Safe use of Electricity

Answer 1

Rigs that use thermionic valves generally require power supply’s (PSU) with potential much higher than domestic mains supply and many external linear amplifiers operate with potential difference of 2kV or more.
Not possible to define a safe potential difference as a single dry cell can start a fire, but it is generally taken that anything over 30v is dangerous.

Question 2

Earthing

Answer 2

All exposed metal services need to be properly earthed including morse keys and microphones. This means providing a low resistance path to Earth so that should a fault occur a high current will flow to Earth rather than through you and fuse protecting the equipment will melt (blow) breaking the supply circuit.

Question 3

Lethal current

Answer 3

Less than 1 amp is enough to stop the heart beating and under lesser fault conditions a lethal current could flow without blowing the fuse. A residual current device (RCD) should be used in order to protect against such faults.

Question 4

Switching off

Answer 4

Wherever possible work on equipment should be done with the power off. Measuring potential difference across circuits must be done with the power one. However, you should always minimise this risk by, where possible, carrying general out resistance checks with power off.