View Single Post
  #10  
Old 01-21-2008, 12:36 AM
Seldom Seen's Avatar
Seldom Seen Seldom Seen is offline
Rising Sun Member
 
Join Date: Aug 2005
Location: Highlands Ranch
Posts: 528
Default T0

Notes on the T0 section - Safety

Electrical safety

- lowest voltage that can cause a shock = 30 V

- lowest current through body likely to cause death = 100 mA (100 milliamperes)

Fuses and wiring

- in a three-way electrical plug, the green wire is connected to ground

- fuses are to interrupt power in case of overload

- never replace a fuse with one that has a greater power rating, or too much current may flow and cause a fire

- to prevent electrical shock, use 3-wire power cords for all equipment; connect all equipment to common ground;

use ground-fault circuit interrupters

- make sure everyone knows where the emergency disconnect switch is

Car batteries (12 V storage batteries)

- can be recharged by connecting to car’s battery and running engine

- contains dangerous acid; short circuits can cause fires; explosive gas can collect

- can overheat or explode if charged or discharged too quickly

Lightning

- when a storm is approaching, disconnect antenna cables and move them away from equipment; unplug all

equipment; stop using radio equipment & stay away from it

- lightning strikes can cause fires

Power supplies contain large capacitors that can shock you even if it is turned off and unplugged.

Outdoor antenna work safety

- when near a tower someone has climbed, wear a hard hat and safety glasses

- before climbing a tower, put on safety belt and safety glasses; arrange for a helper; inspect the tower; make sure no

storms are approaching

- when putting up antennas, make sure people can’t touch them

- when putting up antennas near airports, there are height regulations

- when putting up a tower (or antenna), avoid power lines; if the antenna falls, it should still be more than 10 feet

from the power lines

- tower guy lines are installed according to manufacturer’s instructions

- crank-up towers cannot be climbed unless it is fully lowered

- stainless steel parts are used outdoors to avoid corrosion

- for safety, 8 foot ground rods should be installed at each leg of a tower and bonded together

Radio Frequency (RF) exposure safety

- VHF and UHF signals are considered non-ionizing radiation

- radio waves can be hazardous if too much power is absorbed by the body

- above 30 MHz, more than 50 watts PEP means you need an RF exposure evaluation

- exposure to RF energy depends on the frequency and power of the radio signals, the distance to the antenna, and the

antenna’s radiation pattern

- frequency is important since the body absorbs some frequencies better than others

- you can be sure you comply with the exposure regulations by calculating it using FCC OET bulletin 65 or computer

modeling, or by measuring it using calibrated equipment.

- if you touch antenna while someone transmits, you can get an RF burn

- you can lower exposure by relocating your antennas, altering your antenna patterns, or by changing your station’s

power or frequency

- re-evaluate your exposure if you get new equipment

- exposure is measured in units of milliwatts per square centimeter

- the “duty cycle” of a transmitter affects RF exposure, since the duty cycle determines the time the transmitter is

operating
Reply With Quote