G0 - Electrical and RF Safety

One way that RF energy affects human body tissue is that it heats body tissue. "Time averaging" in reference to RF radiation exposure is the total RF exposure averaged over a certain time.

One property that is NOT important in estimating if an RF signal exceeds the maximum permissible exposure (MPE) is its critical angle. Its duty cycle, power density and frequency ARE important. The power level and frequency of the energy have the most direct effect on the permitted exposure level of RF radiation. When evaluating RF exposure a lower transmitter duty cycle permits greater short-term exposure levels.

An amateur operator must perform a routine RF exposure evaluation to ensure compliance with RF safety regulations. You can determine that your station complies with FCC RF exposure regulations by measurement of field strength using calibrated equipment. A calibrated field-strength meter with a calibrated antenna can be used to accurately measure an RF field. If an evaluation of your station shows RF energy radiated from your station exceeds permissible limits you must take action to prevent human exposure to the excessive RF fields.

With regard to RF safety rules when the maximum power output capability of an otherwise compliant station is reduced, no further action is required.

If you install an indoor transmitting antenna make sure that MPE limits are not exceeded in occupied areas. A ground-mounted antenna should be installed so no one can be exposed to RF radiation in excess of maximum permissible limits. If evaluation shows that a neighbor might receive more than the allowable limit of RF exposure from the main lobe of a directional antenna, take precautions to ensure that the antenna cannot be pointed at their house. Whenever you make adjustments or repairs to an antenna turn off the transmitter and disconnect the feedline.

Any transmitter that contributes 5% or more of the MPE at a multiple user site is responsible for RF safety compliance.

Only the "hot" (black and red) wires in a four-conductor line cord should be attached to fuses or circuit breakers in a device operated from a 240-VAC single-phase source. The minimum wire size that may be safely used for a circuit that draws up to 20 amperes of continuous current is AWG number 12. A 15 amperes fuse or circuit breaker would be appropriate to use with a circuit that uses AWG number 14 wiring.

The most hazardous type of electrical energy is 60 cycle alternating current. The mechanism by which electrical shock can be lethal is current through the heart, which can cause the heart to stop pumping. The maximum amount of electrical current flow that the human body can safely tolerated is 50 microamperes. Current flowing from the hot wire to ground will cause a Ground Fault Circuit Interrupter (GFCI) to disconnect the 120 or 240 Volt AC line power to a device.

The metal chassis of every item of station equipment should be grounded (assuming the item has such a chassis) to ensure that hazardous voltages cannot appear on the chassis. The purpose of a transmitter power supply interlock is to ensure that dangerous voltages are removed if the cabinet is opened.

Any person preparing to climb a tower that supports electrically powered devices should always make sure all circuits that supply power to the tower are locked out and tagged. When climbing on a tower use a safety belt or harness and always attach the belt safety hook to the belt "D" ring with the hook opening away from the tower

A good engineering practice for lightning protection grounds is to insure they are bonded together with all other grounds. It is not safe to use soldered joints with the wires that connect the base of a tower to a system of ground rods because a soldered joint will likely be destroyed by the heat of a lightning strike.

A danger from lead-tin solder is lead can contaminate food if hands are not washed carefully after handling.