V 1 Episode 57 — March 20th, 2017
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Episode 57 -- March 20th, 2017 -- Technician Class Ham License Exam prep, 3 of 3
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V 1.1 International law
* 1.1.1
ITU was founded in Paris in 1865 as the International Telegraph Union. It took its present name in 1932, and in 1947 became a specialized agency of the United Nations. Although its first area of expertise was the telegraph, the work of ITU now covers the whole ICT sector, from digital broadcasting to the Internet, and from mobile technologies to 3D TV. An organization of public-private partnership since its inception, ITU currently has a membership of 193 countries and some 700 private-sector entities. ITU is headquartered in Geneva, Switzerland, and has twelve regional and area offices around the world.
* 1.1.2 The ITU divides the world up into 3 regions for the sake of international Radio Rules. Most of the USA is in Region 2, but there are some territories in regions 1 and 3. This causes a few small differences in frequency assignments for some U.S. Territories different from those in the 50 U.S. States. So if you’re a ham and you’re operating from a boat or a ship at sea, you’ll have different operating frequency privileges, depending on the ITU region you’re in.
* 1.1.3 If you get a Ham Radio license, you can use it whenever you are, subject to the authorization of the country you’re in while operating. Most countries allow ham radio operators to operate, although sometimes with more or fewer privileges than us and you often have to give them months of notice beforehand and sometimes pay hefty fees to do so. A few countries have notified the ITU that it objects to FCC-licensed amateur stations exchanging communications. Check with each country before you try to operate there. Of course, in an emergency, you can talk to anyone you can.
* 1.1.4 When you talk with hams in other countries, the FCC says that you can only discuss Communications incidental to the purposes of the amateur service and remarks of a personal character. I imagine that certain countries don’t want us to discuss politics or certain political philosophies with hams in those countries.
* 1.1.5 Hams are allowed to put the microphone up to the mouth of a person who isn’t a ham radio operator or connect our radios to telephone lines and make calls on behalf of non hams to allow them to talk to people over ham radio. The ham must ALWAYS be in control of the push-to-talk switch. This is called, 3rd party traffic and can only be done in the USA or among countries that allow it. Not all of them do.
V 1.2 FCC Rules, Part 97
* 1.2.1 Code of Federal Regulations 47 is all about the FCC. Part 97 is all about Ham Radio. The FCC has to Answer to the ITU, an United Nations agency for information and communication technology issues.
* 1.2.2
Ham Radio is a "...voluntary noncommercial communication service", and provides, "emergency communications". Hams contribute to Advancing skills in the technical and communication phases of the radio art. Hams Help train operators, technicians, and electronics experts and Enhancing international goodwill. (FCC 97.1).
* 1.2.3 The FCC regulates all radio frequency emissions in United States territories and allows different uses at different frequencies. For example, Part 15 of the FCC rules allows certain unlicensed devices that may emit low powered radio signals on frequencies used by a licensed service.
* 1.2.4 According to the FCC, a Ham Radio Station is A station in the Amateur Radio Service consisting of the apparatus necessary for carrying on radio communications. The station can be at your home, in your car, whoever you are walking around in US Territories or From any vessel or craft located in international waters and documented or registered in the United States
* 1.2.5 The FCC allows a person to conduct radio experiments and to communicate with other licensed hams around the world.
* 1.2.6 But you’re not allowed to broadcast music or earn income or use ham radio in a business. The FCC has other kinds of licenses for those things. You can, however, buy and sell ham equipment when the equipment is normally used in an amateur station and such activity is not conducted on a regular basis, in other words, informal.
* 1.2.7 You can also charge money when giving a ham radio demonstration during instruction at an education institution.
V 1.2.8 Interference
* The main reason why radio has to be licensed is to prevent interference. Harmful Interference is defined by the FCC as That which seriously degrades, obstructs, or repeatedly interrupts a radio communication service operating in accordance with the Radio Regulations
V Ham bands fall into 3 categories of use.
* Exclusive to Hams and therefore cannot be interfered with legally, or
* Shared with another service, but hams are considered, Primary. This means that whenever a ham is causing interference on this band to operations of another service, the other service just has to put up with it. On the other hand, if the other service interferes with a ham, they have to cease transmission or move to another channel. (I’ll often use the words “Channel” and “Frequency” interchangably; they mean the same thing).
* Shared with another service or service(s), but hams are considered secondary. As secondary users, hams are required to not interfere with the other user, up to and including ceasing transmission to prevent such interference. For example, Hams are secondary users on some bands and must always stop transmissions to prevent interference with Radionavigation Service.
* willful interference, done on purpose, is never allowed.
* In order to resolve conflicts between operators of repeater and auxiliary stations, the FCC grants powers to a Frequency Coordinator or Frequency Coordinating Committee to recommend transmit/receive channels and other parameters. A Frequency Coordinator or Frequency Coordinating Committee is chosen by Amateur operators in a local or regional area whose stations are eligible to be auxiliary or repeater stations
* If you and another ham operator are interfering with one another, Common courtesy should prevail, because no one has absolute right to an amateur frequency
V 1.3 Station identification
* 1.3.1 The FCC Issues you a callsign. You can look it up in the FCC’s ULS.
* 1.3.2 When you’re on the air, you say your callsign At least every 10 minutes during and at the end of a communication or a test.
* 1.3.3 If you are participating in a public event such as a race, you and the other participants can use Tactical call signs instead of your regular ones, but you still have to identify with your regular FCC callsign at the end of each communication and every ten minutes during a communication
* 1.3.4 According to the FCC, if you are communicating using voice, you must say your callsign in English or using CW
* 1.3.5 If you are operating away from your normal FCC region, you can give your callsign followed by either “Stroke”, “Slant” or “Shash” and then the region or country code where you are. In CW, use a “/“ character. Ditto if you’ve just upgraded and your upgrade hasn’t yet appeared in the FCC’s ULS. Use either /KT, /AE or /AG.
V 1.4 Operator licensing
* 1.4.1 Ham callsigns in the USA start with A, N, W or K
* 1.4.2 Callsigns have 1 or 2 letters and then a single digit and then 1, 2 or 3 letters. The FCC grants Special Event callsigns for special events with a single letter and a number and a single letter.
* 1.4.3 The FCC allows Any licensed amateur to ask for a vanity call sign. A technician class licensees to ask for a vanity call sign (choose your own) but only with 3 letters at the end. Extra class licensees can get a 2x1 or 1x2.
* 1.4.4 If you have at least 4 members, your club can get a license. The person named as trustee on the club station license grant can ask for a vanity call sign for the club.
* 1.4.5 You listen to my radio show. You study this guide. You fill out some forms. You show up with your government issued ID and pay your $15. You take and pass a test. You get a license. You can start operating as soon as your operator/station license grant appears in the FCC's Universal Licensing System (ULS) online at fcc.gov.
* 1.4.6 It lasts 10 years and is renewable.
* 1.4.7 If you forget to renew your license after 10 years, you still have a 2 year grace period in which to do so. You cannot transmit until the FCC's Universal Licensing System (ULS) online at fcc.gov says your license has been renewed.
* 1.4.8 If the FCC writes you a letter at the address you gave them and it is returned as undeliverable, they might revoke your station license or suspend your operator license.
* 1.4.9 There used to be Novice Licenses and Advanced licenses, and Technician Plus licenses but not anymore. The only ham radio licenses now are Technician, General, and Amateur Extra.
V 1.5 Authorized and prohibited transmission
* 1.5.1 Indecent or obscene language is prohibited
* 1.5.2 Messages not in a plane language (with the exception of Satellite Telecommand codes)
* 1.5.3 Music (with the exception of Spacecraft who have the music on in the background)
* 1.5.4 During military communications tests, hams can exchange messages with a US military station.
* 1.5.5 Auxiliary, repeater, or space stations can automatically retransmit the signals of other amateur stations.
* 1.5.6 Hams may broadcast morse code practice or information bulletins
* 1.5.7 Broadcasting means Transmissions intended for reception by the general public
* 1.5.8 In an emergency, when no other means is available, hams can broadcast news, program production, or gather news, but only where such communications directly relate to the immediate safety of human life or protection of property.
* 1.5.9 You can’t transmit messages in exchange for money. In fact, you can’t ask for any money for just about anything having to do with Ham Radio (Except buying and selling used equipment individually, informally and if you’re part of an educational institution and you’re demonstrating ham radio in a class; they do this for astronauts at NASA).
V 1.6 Operator Privileges and Frequencies
* 1.6.1 The exact chart that shows on which parts of which bands you can operate which modes using which operator’s license level is called a Band Plan. While the FCC considers the band plan voluntary with respect to modes, it is a rule with respect to operator privileges.
V 1.6.2 You should not operate too close to the band edges
* Radios are not perfect; they can get out of calibration. That’s just a frequency display and not a frequency counter.
* Even if your rig is totally on frequency, sometimes, over time, as it warms up, it might drift
* Each mode takes up some bandwidth. So even if you’re exactly on the mark, as you talk, your sidebands will get bigger with your speech.
V 1.6.3 You can use CW on any ham band
* You can use SSB or AM on at least some portion of all the amateur bands
* Lower sideband for 160, 80 and 40 meters
* Upper sideband for 20, 17, 15, 12 and 10 meters
* You can use FM on some portion of each band from 28 MHz and up.
V 1.6.4 Remember that the speed of light and radio waves, 300 million meters per second divided by the wavelength in meters is equal to a frequency somewhere close to the bad.
* The 6m band goes from 50 - 54 MHz
* The 2m band goes from 144 - 148 MHz. The national calling frequency is 146.52 MHz.
* The 1.25m band goes from 222 - 225 MHz, but data only can be used from 219 - 220 MHz
* The 70cm band goes from 420 - 450 MHz. The national calling channel is 446.0 MHz.
* The 33cm band goes from 902 - 928 MHz
* The 23cm band goes from 1240 - 1300 MHz
V The 6 meter, 2 meter, and 1.25 meter bands have mode-restricted sub-bands for technician class hams.
* Generally, the first 100 KHz of every band is for CW only. For example, 144.0 - 144.1 MHz.
* 1.6.5 While not exceeding the maximum power permitted on a given band, use the minimum power necessary to carry out the desired communication
V 1.6.6 Control operator and control types
V When the FCC gives you a license, it’s really 2 licenses in 1: a Station license for your equipment and an operator’s license for you. Each set of station equipment, even a handitalkie is licensed as a station license and each person who gets a ham license is a control operator when using such equipment. You can loan your equipment to another ham, even one from outside the country, but they have to only use it within the limits of their operator’s license. Even Repeaters have a control operator — that’s the ham who is listening in case of a problem and can shut the repeater down remotely if needed. No amateur station can transmit without a control operator. Whoever is the station licensee designates the station control operator. The Control Operator and the Station Licensee are equally responsible for proper operation of the station.
* T1E02 (D) [97.7(a)]
Who may a station licensee designate to be the control operator of an amateur station?
A. Any U.S. citizen or registered alien
B. Any family member of the station licensee
C. Any person over the age of 18
D. Only a person for whom an amateur operator/primary station license grant appears in the FCC database or who is authorized for alien reciprocal operation
* T1E03 (A) [97.103(b)]
Who must designate the station control operator?
A. The station licensee
B. The FCC
C. The frequency coordinator
D. The ITU
V Every station has a control point, whether that’s near the transmitter or remote. That’s where the control operator function is performed. The control they’re talking about here is the PTT switch and the ability to override it.
* Local control is where the control operator is at the controls of the transmitter directly.
* Remote control is where the control operator can control the transmitter from another radio or over the internet or a telephone.
* Even repeaters and APRS network digipeaters have a control operator, but since they work under Automatic Control, the control point is always somewhere else such as over the internet or a radio. Contrast that with the Local control or Remote Control which must be used for all other types of transmissions besides those from repeaters, auxiliary stations and satellite transponders.
* Unless there’s specific documentation saying otherwise, FCC presume to be the control operator of an amateur station to be The station licensee
* An FCC representative can ask to inspect the station or its records at any time.
V 1.7 Operating
* 1.7.1 CQ means “Seeking You” or Calling any station
V 1.7.2 When you first get on the air on HF, you’ll want to try to talk to somebody and most likely, you’ll either listen for somebody else calling CQ or do it yourself.
* Make sure you’re in a band where you’re allowed via your license and mode
* Listen first to make sure nobody’s using that frequency. Remember that maybe you can hear only 1 side of the conversation
* Verbally ask “Is the frequency in use?”
* 1.7.3 Since repeaters are guarrenteed that if you can get into it, everybody can hear you, we don’t use CQ on a repeater. Mostly, we might say something like, “WB5QAL Listening”.
* 1.7.4 If you’re trying to reach a specific station or answering somebody’s CQ call or “so-n-so listening”, briefly give the other station's call sign followed by your call sign.
* 1.7.5 If you’re on HF or if you’re mobile, the FCC recommends that you identify Using a phonetic alphabet to make sure everybody understands your callsign correctly.
* 1.7.6 To help identify where hams are located, there is an international standard Grid Square Map. A letter-number designator assigned to a geographic location is a “grid square”. My home is in CM89. KPFZ is closer to CM88.
* 1.7.7 Some hams participate in contests, contacting as many stations as possible during a specified period of time. Because everyone’s going as fast as they can, Send only the minimum information needed for proper identification and the contest exchange. Usually signal strength, location and some brief info about the contest, such as a designation for your equipment or station size.
V 1.7.8 In morse code, we often use Q signals to indicate specific common phrases
* QRM = interference caused by humans; “Somebody is QRMing us - try 5 KHz up”.
* QRN = atmospheric interference. “I am experiencing QRN mixed with your signal; I can’t hear you.”
* QTH? = Where are you? — QTH = My QTH is Lake County
* QSY? = “Please change frequencies to …” ; QSY = “I am changing frequency to …”
* QSB? = “Does my signal strength vary?”; QSB = “Your signal strength is going up and down
* QRU = “I have nothing for you”; QRU? = “Do you have anything for me?”
* QRS = Send more slowly
* QRZ? = “Was someone calling me?”
V 1.8 Satellite and Radio Control operation
* Hams have a few satellites. Ham satellites have Transponders. A Transponder is like a repeater but instead of listening on just one frequency for one person to talk, it listens on a portion of a whole band and repeats the whole band portion and everyone’s conversation on another band. If you have the license privilege to talk on the satellite’s input band, you can use one.
V We use satellite tracking programs to see Maps showing the real-time position of the satellite track over the earth and The time, azimuth, and elevation of the start, maximum altitude, and end of a pass and The apparent frequency of the satellite transmission, including effects of Doppler shift.
* time, azimuth and elevation
V Orbits
* LEO - Low Earth Orbiting Satellites are so close that they move much faster and can sometimes be seen twice or more often in 1 day.
Geosynchronous - An orbit around Earth whose orbital period is equal to a sidereal day (23 hours, 56 minutes), irrespective of its inclination.

- A person on a point on Earth, will see a satellite in this orbit in the same place in the sky at the same time of the day, everyday.

Geostationary - A geosynchronous orbit around Earth at 35,786 km above the equator, so that it remains stationary as seen from Earth.

- A person on any point on Earth, will see a satellite in this orbit stationary w.r.t his position, just like a star in the sky.
* Doppler shift is An observed change in signal frequency caused by a change in distance between the satellite and the earth station. Think of a train whistle, changing its pitch as it comes closer and then goes farther away.
V The Keplerian Elements are a set of numbers which allow satellite tracking programs (or really patient humans) to calculate a satellite's position in space. Named after (wikipedia) Johannes Kepler, (1571-1630), German astronomer who discovered what we call the three major laws of planetary motion.
* (1) the planets move in elliptical orbits with the Sun at one focus;
* (2) the time necessary to traverse any arc of a planetary orbit is proportional to the area of the sector between the central body and that arc (the “area law”); and
* (3) there is an exact relationship between the squares of the planets’ periodic times and the cubes of the radii of their orbits (the “harmonic law”).
* Kepler regarded these as celestial harmonies reflecting God’s design for the universe. We call them laws. Kepler’s discoveries turned Nicolaus Copernicus’s Sun-centred system into a dynamic universe, with the Sun actively pushing the planets around in noncircular orbits.
* You should only use enough power to complete the contact
V Many astronauts are hams. The Ham license training is an optional part of Astronaut training. So the ISS often has hams aboard.
* If you have a technician license, and they’re available, you can talk with them.
* If you’re talking to somebody in a manned spacecraft, they’re allowed to have music on incidental to an authorized retransmission of manned spacecraft communications
* Satellites often transmit information about themselves using a beacon, which is just a fancy word for a transmitter that sends out some kind of data that the inventor of the beacon thought might be useful or interesting to somebody. The most popular kind of data to send is telemetry. According to the FCC, Telemetry is defined as a one-way transmission of measurements at a distance from the measuring instrument
* And, while we’re on the subject, A one-way transmission to initiate, modify or terminate functions of a device at a distance is called Telecommand. These are required for satellite operating, in case nobody is there to stop the transmitter. It's okay to transmit one way, not expecting a reply.
* Telecommand is also used to control radio-controlled vehicles on ham frequencies up to a maximum transmit power of 1 watt. You don’t have to identify. Instead, A label indicating the licensee's name, call sign and address must be affixed to the transmitter.
* Telecommands may be encrypted to hide their contents. But that is the only situation in which hams are allowed to have secret communications. All others must be in plane language.
* Most satellites have more than one transponder. We talk about them by using terminology such as U/V to mean a UHF uplink and a VHF downlink. That is, in order for you to talk though a satellite transponder operating in U/V mode, you must transmit your SSB or CW or FM or FM packet digital signal on UHF (70cm) and receive the satellite’s transmissions of your signal and that of whoever responds to you on VHF, or 2 meters.
* Satellites have a different kind of noise than normal radio communications. Rotation of the satellite and its antennas causes spin fading.
* There are digital satellites which only work for FM Packet Radio
V 1.9 Station setup
V Some hams use computers
* Satellite tracking
* For logging contacts and contact information
* For sending and/or receiving CW
* encoding and decoding digital signals using a Terminal node controller or a sound card to the mic and speaker jacks of the radio
* Seeing a graph in real time of the conditions of the band
* Programming VHF and UHF radio frequencies from a spreadsheet like application
* Seeing a map of APRS stations
V In the car
* Since most ham equipment runs off of 12vdc and most ham homes have 120vac, it stands to reason that most hams use regulated power supplies. The regulation prevents voltage fluctuations from reaching sensitive circuits which might otherwise make objectionable hum along with your transmissions
* The alternator in your car produces square waves as it turns on and off as it rotates so it produces a lot of RF noise. On the radio, this sounds like high-pitched whine that varies with engine speed
* When wiring a rig in the car, try to attach the ground wire At the battery or engine block ground strap
* Just as you can adjust the volume control on your receiver so that it doesn’t distort the sound coming through your speaker, there is also a microphone gain control to adjust the level for different people to be able to talk clearly, some loud, some soft. If it’s turned up too loud, the sound might become distorted on transmit, too.
V at home
* So you have a power supply and radio and mic and key connected perhaps through an amplifier and then an SWR meter and then perhaps through an antenna tuner and finally you’ll want to connect a filter to reduce harmonic emissions Between the transmitter and the antenna
* Best to use a solid Flat strap for grounding the station to a ground rod
* Another popular source of distortion while your listening to an AM or single sideband receiver is hash from power lines. Noise Blanker circuits are designed to mitigate this.
* Automatic Gain Control is like an automatic volume control that keeps the signal the same loudness while you’re listening, even as it fades up and down in strength
* The best way to hear signals on HF is to set your receiver bandwidth so that it only picks up a big enough chunk of the band to hear the signals you’re looking for. If that’s CW, then 250 or 500 Hz is plenty. For USB and LSB, you can get by with as little as 1.6 kHz, but normally 2400 Hz is considered optimal.
* Nowadays, all HF radios have receive and transmit VFO and all VHF and UHF radios have computers controlling a frequency synthesizer so that you can use a keypad or knob to tune any channel and then store it in a memory channel for quick access
* When you listen to a single sideband signal, as you turn your VHF knob, you’ll hear part of it then the center (where you’ll hear all of it) and then the other side. Because of this, all modern radios have RIT or Receiver Incremental Tuning to allow you to change your receive frequency but stay transmitting on the same frequency so the person with whom you’re conversing doesn’t chase you down or up the band.
* In the old days, you’d have a receiver and a transmitter and they would each have a crystal to specify precisely what frequency upon which you could listen and talk. Later, everybody changed their receivers so that instead of a single crystal controlling a single local oscillator, there would be a variable capacitor to adjust a tuned circuit to change the frequency so that you could turn the VFO knob to hear stations on different frequencies.
V 1.10 Traffic Handling
* 1.10.1 To further the FCC’s aim that ham radio operators provide public service, there has been a culture in ham radio of playing the game of telephone for passing messages between non-hams to aid during disasters and public events. This is much less prevalent since the advent of cellular phones, but still practiced.
* 1.10.2 Obviously the goal is to pass messages exactly as they were received.
* 1.10.3 Messages are in a standard format including a preamble which includes The information needed to track the message as it passes through the amateur radio traffic handling system followed by the contents of the message itself, usually fewer than 30 words long with only question marks and periods and commas for punctuation, rather like a telegram. Anyone can pass messages to a ham to send anywhere in the world where 3rd party traffic is permitted and them message should arrive within a few days. This is a free service that hams perform to keep in practice.
* 1.10.4 When Passing messages via voice including proper names or unusual words, such words and terms should be spelled out using a standard phonetic alphabet
* 1.10.5 The past part of the preamble of each message is a check. This refers to the counted number of words and punctuation marks in the body of the message itself, not including the preamble.
V 1.11 Public Service
* 1.11.1 Radio Amateur Civil Emergency Service and Amateur Radio Emergency Service are two separate organizations that may provide communications during emergencies
* 1.11.2 ARES is a group of Licensed amateurs who have voluntarily registered their qualifications and equipment for communications duty in the public service
V 1.11.3 RACES
* A radio service using amateur frequencies for emergency management or civil defense communications
* A radio service using amateur stations for emergency management or civil defense communications
* An emergency service using amateur operators certified by a civil defense organization as being enrolled in that organization
* 1.11.4 During emergencies, one station will act as a net control operator on a given frequency or channel. Since almost all of our radio equipment is designed to work in half-duplex operation as opposed to full duplex, it is necessary to know who is supposed to begin talking when somebody else stops. It is always the net control operator who gets to speak and ask everybody else to answer him or her.
* 1.11.5 Therefore, when an emergency occurs and you’re at a radio, find a local net and listen for the net control operator to ask for checkins. Follow the instructions (usually by saying your callsign when they ask for checkins and letting them know your location or whatever information they ask you for. Then, remain on frequency without transmitting until asked to do so by the net control station.
V 1.11.6 IN an emergency, an accepted practice to get the immediate attention of a net control station is to begin your transmission by saying "Priority" or "Emergency" followed by your call sign.
* “Priority” means having to do with the safety of property of the safety of people’s or animals lives which are not in immediate danger.
* “Emergency” is a word only used to refer to an immediate life-threatening situation
* 1.11.7 In an actual emergency, you can transmit wherever you need to to resolve the emergency, but only if necessary in situations involving the immediate safety of human life or protection of property
V 1.12 Electrical Safety
* If you charge or use up a lead-acid storage battery too fast, it can overheat and give off flammable gas or explode
* If you Short the terminals, it can cause burns, fire, or an explosion
V Electrical current flowing through a human body
* physically heats tissue, like a microwave oven heats meat
* disrupts the electrical functioning of cells
* causes involuntary muscle contractions
V The electricity coming into your home starts out as 3 phase 240 volt 60 cycle AC
* Red and Black are hot
* White is neutral - white to red and white to black are 120 vac
* Green is ground
V Fuses and circuit breakers exist to break a circuit rather than heat up wires beyond their capacity.
* For example, if you have a circuit which requires a 5 amp fuse, that means that the wires in that circuit and other components can only accommodate up to 5 (or, more likely, 4 or less) amps. If you change that 5 amp fuse for a 20 amp fuse, that means that if a component fails and you accidentally end up with 19 amps flowing through the circuit, then those components the fuses is there to protect will fail instead of the fuse. If one of those components is a wire passing too close to something flammable, than that wire will heat up and possibly start a fire.
V Guard against electrical shocks at your ham station:
* Use 3 wire cords and plugs for all AC equipment and connect the ground wire to chassis ground
* Connect all AC powered equipment in your station to a common ground
Plug it all into a GFCI outlet. “A GFCI is much more subtle. When you look at a normal 120-volt outlet in the United States, there are two vertical slots and then a round hole centered below them. The left slot is slightly larger than the right. The left slot is called "neutral," the right slot is called "hot" and the hole below them is called "ground." If an appliance is working properly, all electricity that the appliance uses will flow from hot to neutral. A GFCI monitors the amount of current flowing from hot to neutral. If there is any imbalance, it trips the circuit. It is able to sense a mismatch as small as 4 or 5 milliamps, and it can react as quickly as one-thirtieth of a second.
So let's say you are outside with your power drill and it is raining. You are standing on the ground, and since the drill is wet there is a path from the hot wire inside the drill through you to ground (see How Power Distribution Grids Work for details on grounding). If electricity flows from hot to ground through you, it could be fatal. The GFCI can sense the current flowing through you because not all of the current is flowing from hot to neutral as it expects -- some of it is flowing through you to ground. As soon as the GFCI senses that, it trips the circuit and cuts off the electricity. http://home.howstuffworks.com/question117.htm
According to a 1999 study by the American Society of Home Inspectors, 21% of GFCI circuit breakers and 19% of GFCI receptacles inspected didn't provide protection, leaving the energized circuit unprotected. In most cases, damage to the internal transient voltage surge protectors (metal-oxide varistors) that protect the GFCI sensing circuit were responsible for the failures of the protection devices. In areas of high lightning activity, such as southwest Florida, the failure rate for GFCI circuit breakers and receptacles was over 50%!
GFCIs will also fail if you wire them improperly. The most important thing to remember when wiring them is to connect the wire originating at the breaker to the line side of the GFCI and the wire connecting downstream to the load side of the device. The GFCI terminals are clearly marked “Line” and “Load.”. http://ecmweb.com/basics/how-gfcis-work
* Mitigate lightning strikes on your antennas by grounding through lightning protectors such as gas-discharge type and ground all of them to the earth and each other.
* When you build equipment which plugs into the wall (such as a power supply) always include a fuse or circuit breaker in series with the AC hot conductor
* Remember that, if you build a power supply, it might have very big capacitors which store electrical energy, even when the power is removed it can shock you.
* When working on a tower with others, always wear a hard hat and safety glasses because the FCC rules say you should. Safety glasses around a tower might be useful if you’re welding or looking up when somebody drops a screw, …ditto hard hat
* Even climbing a tower, the FCC wants you to wear safety glasses with your climbing harness.
* They also insist that you never do it alone, even if it’s just 20 feet up.
* DO identify all the overhead electrical wires and place your mast or tower and antenna system so that, if it fell, it wouldn’t fall within 10 feet of the wires. Duh.
* DO use a gin pole to lift tower sections because it is the easiest way to put up a tower if you don’t own a giant crane
* DO NOT climb a telescoping or crank-up tower unless it is all the way retracted.
* DO use a separate 8 ft ground rod for each leg of the tower and bond them to each other also. DON’T make sharp bends in the wires. DO Ensure that connections are short and direct
* DO NOT use a utility pole to hold up your antenna because you might be a moron and place it in such a fashion as to accidentally touch high voltage wires if it were to blow away or break or fall.
* Tower Grounding requirements are specified by local electrical codes