key word: UNAUTHORIZED. A locked switch in line with the electrical circuit feeding the station would prevent unauthorized operation of the station.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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key word: UNAUTHORIZED. A locked switch in line with the electrical circuit feeding the station would prevent unauthorized operation of the station.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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key words: HIGH-VOLTAGE. Devices operating with high voltage should always include an 'interlock' switch so they power down when cabinets are open to prevent electrocution.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Under certain circumstances, even 30 VOLTS can be dangerous. If the human heart is part of the electrocution path, even one tenth of an ampere can lead to cardiac arrest. Wet skin or cuts to the skin and the exact path of the current are all factors that determine the severity of electrocution.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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key words: "MAINS" OPERATED. This refers to 'Household' current which runs at 120 volts and can supply hundreds of amperes (for a brief time) before a fuse or breaker interrupts the circuit after a fault. 30 VOLTS is considered potentially dangerous to humans and less than A TENTH of an AMPERE can lead to cardiac arrest.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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This was especially true of transmitters using vacuum tubes. Plate voltages ran into the hundreds of volts with current capacities of hundreds of milliamperes. 30 VOLTS is considered potentially dangerous to humans and less than A TENTH of an AMPERE can lead to cardiac arrest.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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An external ground connection on each cabinet serves as a backup to the normal electrical outlet ground ( the 'green' wire in a three-lead power cord ).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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An external ground connection on each cabinet serves as a backup to the normal electrical outlet ground ( the 'green' wire in a three-lead power cord ).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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'Copper-Clad' ( steel core, copper plating ) offers rigidity (when hammering the rod into the ground) and conductivity (for best ground connection).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Like everything else about electricity, station and antenna system grounding is governed by the electrical Code applicable to your province. Typically inspired by the "Canadian Electrical Code" (CSA Group, formerly Canadian Standard Association), provincial requirements are often appended to the national code.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The 'green wire' in a three-wire AC line cord is a ground connection. Securing the 'green wire' to the chassis (and outside cabinet) keeps the chassis at ground potential if a fault ever caused the 'live' side (120 volts) of the AC line to contact the chassis.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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key word: 10 METRES. RF 'hot spots' and RF 'burns' are symptoms of 'Stray RF'. This is relatively long in comparison with some of the wavelengths in the HF (High Frequency) spectrum. For example, 10 metres is a quarter wavelength on the 40 metre band. A wire this long looks like an antenna and will not provide a low impedance ground connection necessary to evacuate 'Stray RF'.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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RF 'hot spots' and RF 'burns' are symptoms of 'Stray RF'. To eliminate 'Stray RF', a low impedance path to ground must be provided. Only SHORT and WIDE ground conductors can provide low impedance.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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RF 'hot spots' and RF 'burns' are symptoms of 'Stray RF'. To eliminate 'Stray RF', a low impedance path to ground must be provided. Only SHORT and WIDE ground conductors can provide low impedance.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The 'green wire' in a three-wire AC line cord is a ground connection. Securing the 'green wire' to the chassis (and outside cabinet) keeps the chassis at ground potential if a fault ever caused the 'live' side (120 volts) of the AC line to contact the chassis.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The 'green wire' in a three-wire AC line cord is a ground connection. Securing the 'green wire' to the chassis (and outside cabinet) keeps the chassis at ground potential if a fault ever caused the 'live' side (120 volts) of the AC line to contact the chassis.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The lightning arrestor must be outside to prevent as much energy as possible from entering the premises. It must be close to ground so that a path with the least possible impedance (resistance + inductance) can divert the most energy into the ground. Peak voltage between the transmission line and ground is thus minimized. Rise time in a lightning bolt is measured in microseconds (i.e., high frequency); voltage is high and current is zero in the first instant an inductance is subjected to a pulse.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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If station equipment is totally disconnected from external circuits (power and antenna), damage to station equipment from lightning or voltage surges become impossible.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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'Fall prevention' is a serious matter. In Canada, worker safety is a provincial responsibility. A 'safety harness' and 'hard hat' are minimum requirements.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Even at modest power, touching a radiating antenna or open-wire line can lead to 'RF burns'. Voltage is not the only factor, radio frequency reaches deep into the skin, potentially causing nasty burns. Suspending an antenna above electric lines is a dangerous mistake: if the antenna dropped, lethal voltages would be carried back to the station.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Even at modest power, touching a radiating antenna or open-wire line can lead to 'RF burns'. Voltage is not the only factor, radio frequency reaches deep into the skin, potentially causing nasty burns.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
Even at modest power, touching a radiating antenna or open-wire line can lead to 'RF burns'. Voltage is not the only factor, radio frequency reaches deep into the skin, potentially causing nasty burns.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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"Disconnecting the transmission line", that is an important precaution to ensure that no RF is ever sent to the antenna. This is especially important if there are several parties in the work crew: an operator could return to the station, turn-on a transmitter and put someone outside at risk.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Even at modest power, touching a radiating antenna or open-wire line can lead to 'RF burns'. Voltage is not the only factor, radio frequency reaches deep into the skin, potentially causing nasty burns.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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RF energy can heat body tissue. 1000 MHz is generally considered to be the low end of the MICROWAVE spectrum. Microwave energy has long been known for its 'heating' effect ( think "microwave oven" ). Never point antennas at anyone. Never look into antennas. Disconnect transmission lines before working on antennas (to further reduce the odds of an error at the station exposing to RF).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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RF energy can heat body tissue. VHF and UHF frequencies present the greatest risk. Never point antennas at anyone. Never look into antennas. Disconnect transmission lines before working on antennas (to further reduce the odds of an error at the station exposing to RF).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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RF energy can heat body tissue. VHF and UHF frequencies present the greatest risk. 30 MHz to 300 MHz is the range of radio frequencies over which Health-Canada's "Safety Code 6" recommends the lowest exposure level.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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RF energy can heat body tissue. VHF and UHF frequencies present the greatest risk. 30 MHz to 300 MHz is the range of radio frequencies over which Health-Canada's "Safety Code 6" recommends the lowest exposure level.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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RF energy can heat body tissue. VHF and UHF frequencies present the greatest risk. 30 MHz to 300 MHz is the range of radio frequencies over which Health-Canada's "Safety Code 6" recommends the lowest exposure level.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The inside of the eye is mostly liquid. Ever seen a cup of water brought to a boil in a microwave oven ? RF energy can heat body tissue. VHF and UHF frequencies present the greatest risk. 30 MHz to 300 MHz is the range of radio frequencies over which Health-Canada's "Safety Code 6" recommends the lowest exposure level. Keep antennas away from your head.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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RF energy can heat body tissue. VHF and UHF frequencies present the greatest risk. 30 MHz to 300 MHz is the range of radio frequencies over which Health-Canada's "Safety Code 6" recommends the lowest exposure level.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
RF energy can heat body tissue. VHF and UHF frequencies present the greatest risk. Never point antennas at anyone. Never look into antennas. Disconnect transmission lines before working on antennas (to further reduce the odds of an error at the station exposing to RF).
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
Even at modest power, touching a radiating antenna or open-wire line can lead to 'RF burns'. Voltage is not the only factor, radio frequency reaches deep into the skin, potentially causing nasty burns.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none