Transcript SAFETY
SAFETY How to Enjoy Ham Radio and Live While Doing it. Power Sources • Voltage nominally 115/230 varies greatly. • Wired with #14 wire to provide 15 amps/1500 W per circuit. • Third ground wire may not be present in some old homes. Station Safety Ground No Safety Ground With Safety Ground • All metal cabinets containing voltages in excess of 40-50 volts should be grounded using a 3-wire power cord. • Do not eliminate the ground pin from a 3wire plug. Station Ground • Can use cold water copper pipe. • Do not use hot water line or cold water line if it is plastic. • Do not use gas line. • All connections should be both physically and electrically well made and permanent. • Better is separate ground rod. Copper clad rod 3.23 Metres (10 Ft) long. Or ground plate( square copper clad steel plate 30 Cm on a side buried to a depth of 45 CM. • The length of the ground cable can be a problem. If the line is ¼ of a wavelength( or a multiple of this length) it can act as an antenna. • All grounds in the station should be connected together securely at a single point. Power Requirements • Ideally the station should be provided with a dedicated circuit. • Station lights should be on a separate circuit. Problems with station power will not cause instant darkness. Electrical Safety • Voltage in vacuum tube rigs can be in excess of 5000 volts. • This voltage can be present in power supply filter capacitors long after the power is disconnected. Procedure for Working on High Voltage Equipment • Remove power cord from the outlet. • Wait 3 minutes. • Using a single hand (other one in pocket) use a shorting stick. Shorting Stick • If it is necessary to work on a rig with the power on work with a single hand standing on a rubber mat. Never wear headphones. If possible don’t work alone. • Interlocks while providing some safety are not foolproof. For example they do not assure that the capacitors are discharged. Dangers of Electricity • We can feel a current of 1-2 mA. • 10 mA causes pain • A current of 10-100 mA causes muscular paralysis, severe physiological shock, and extreme difficulty breathing. • Above 100-200 mA death becomes increasingly likely. What to do Case of Shock 1. Survey the area to ensure your own safety. 2. Turn off the source of current. You don’t want to create two casualties. 3. If it is going to take an excessively long period of time to use a non conductor to remove the victim from the current source. Be sure that what you are using is a non conductor. A dirty or wet robe can be a conductor when the source is a high voltage. 4. If the victim has stopped breathing start artificial respiration. 5. If there is no pulse start cardio pulmonary resuscitation CPR 6. Learn First Aid Antenna Safety • Never install an antenna where it can come in contact an electrical line. • The far ends of dipoles and inverted vees have high RF voltage on them capable of causing burns. Make sure that they do not come in contact with people or animals. • Beam antennas should be high enough that you are not sending RF energy directly at someone’s home. • End fed antennas will have high RF voltages on them at the ends and possibly other places as well. • Open wire transmission lines will have high RF voltage spaced along their length. • Do not use a hydro pole or the electrical stack of a house as a support point for an antenna. • Antennas can be heavy and when working on a tower you may not have the leverage to swing the antenna. Tower Safety • Always use a safety Belt. • Use Belt and Suspenders approach. Ie use two safety straps. • Use a Gin Pole. Gin Pole • Never stand under a tower while sections are being raised. • All towers are rated in terms of the maximum size of antennas they will support usually in terms of wind surface area or wind loading. • Check with your insurance agent to determine if you are covered should your antenna come adrift. Lightning Protection • Minimize the possibility of direct lightning strike. • Minimize the damage caused by a direct strike. • Minimize the damage caused by a nearby strike. • Minimize the damage that may be caused by a build-up and discharge of static electricity. • Current very high. • As a result very high voltages can be induced between sections of the antenna and the ham shack. • The rise time of a lightning bolt is very short so a lightning bolt has an effective frequency of several mHz. All ground lines therefore should be as short and as direct as possible. • There is evidence that damage from a lightning strike on a raised metal object can be reduced by suitable grounding. Damage Minimization • Ground each leg of tower individually. Connect each ground rod together, then connect all ground rods for your antennas together and to the electrical ground of the house. • At the base of a vertical or end fed antenna connect an RF choke made of large gauge wire between the end of the antenna and ground. Alternatively securely ground the antenna when not in use. • Use static arrestors to remove static electricity from coax cable. • Use spark gap arrestor to eliminate static electricity on open wire feedlines. Spark Gap Lightning Protector • Design your system so that it is easy to disconnect all lines entering your house and connect them to ground when the station is not in use. When not in use unplug all power connections and telephone and modem connections when the station is not in use. • Never operate when there are electrical storms in the vicinity. Exposure to RF • Energy of any portion of the electromagnetic spectrum is directly proportional to the frequency. • Microwave operates at 2.45 GHz but we are protected by a Farady Cage. • Diathermy uses a frequency of 27.12 MHz so all ham radio frequencies can transfer energy to the human body. • Do everything to limit your body’s exposure to RF energy. • Keep the antenna away from the body while transmitting. Can be a problem in the winter when handheld must be near body to keep the battery warm enough to keep working. • Health Canada in its Safety Code 6 warns about the dangers of and sets limits for RF body exposure. • When working on antennas ensure that your transmitter is switched off. (perhaps unplug it) • The gain of an antenna can increase the energy in the preferred direction substantially over what might be suggested by the transmitter power. • Antennas such as long wires may extend the high current node (High RF field strength) into the operating area. Soldering • A 150 watt soldering iron can cause significant burns for quite a while after it is unplugged. • Molten solder on bare skin hurts. • An unattended soldering iron can start fires.