Get your ham radio license.

The FCC is the government agency in charge of radio in the United States, and Part 97 is its rulebook for ham radio. Your license makes you the control operator of your station, which means you are responsible for everything your station sends out, even if a guest is talking. You identify your station by saying your call sign at least every 10 minutes while you talk, and again at the end. Ham radio is for licensed people talking to licensed people: no music, no broadcasting to the general public, no secret codes meant to hide what you mean, and you cannot be paid to transmit except for a few narrow cases, like a teacher using radio in a classroom. Use only the power you need. A Technician's ceiling is 200 watts PEP in those HF segments, and 1,500 watts PEP on the frequencies above 30 MHz, and the minimum-power rule applies everywhere. If the FCC sends you a letter about your station, answer it fully and honestly.

Start with why the service exists at all, because the FCC states it in the rules. Part 97 opens with the Basis and Purpose of amateur radio, and one of its named purposes is advancing your skills in the technical and communication phases of the radio art. You are not just allowed to learn how radio works; learning is part of the point of the license. The service also exists to grow the pool of trained operators, but when a question asks what the Basis and Purpose includes, the skills answer is the one they want.

Here is how the license itself lands, since nobody mails you a paper license anymore. After you pass, the FCC emails you a link to download your license grant. The grant is real when it appears in the FCC's ULS database, and that listing is the proof of your license. You may get on the air as soon as your grant shows in the database; you do not wait for anything to arrive in the mail. Keep your email current with the FCC, because that address is their line to you: if the FCC cannot reach you by email, they can revoke the station license or suspend the operator license. A renewal can be filed starting 90 days before your expiration date. And know what the two-year grace period does not do: if your license expires, you may renew inside the grace period, but you may not transmit until the renewal is granted.

The FCC issues new licenses for three classes only: Technician, General, and Amateur Extra. Any licensed amateur may also pick a vanity call sign when one is available. Call signs come in formats, and the plain sequential format a new Technician receives is Group D, which looks like KF1XXX: two letters, a digit, and three letters. A club can hold a station license too, as long as the club has at least four members. Two more situations the rules cover: in international waters, you may operate from a US-documented vessel or craft with the master's permission, and your station and your station records must be open to inspection at any time an FCC representative asks.

Some people keep the whole system coordinated. A Volunteer Frequency Coordinator recommends the transmit and receive channels that repeaters and auxiliary stations use, so two repeaters do not land on top of each other. The coordinator is chosen by the amateur operators in that local or regional area whose stations are eligible to be repeater or auxiliary stations. A few definitions ride along with this group: a space station is any amateur station located more than 50 km above the Earth's surface, and automatically controlled propagation beacons, the stations that exist so you can hear how far the band is open, live on ten meters between 28.200 and 28.300 MHz. RACES, the Radio Amateur Civil Emergency Service, has an extra requirement beyond your license: certification that you are currently enrolled with a civil defense organization.

Now the band and power facts a Technician actually gets tested on. Your voice privileges on HF exist on one band only: 10 meters, from 28.300 to 28.500 MHz. On parts of 80, 40, and 15 meters your privileges are CW, and on 10 meters you get CW and data as well as phone. Digital modes like FT8 are open to you on 10 meters and throughout your VHF and UHF bands. Two slices at the bottom of 6 meters and 2 meters, 50.0 to 50.1 MHz and 144.0 to 144.1 MHz, are CW only. Learn to read a frequency and name its band: 52.525 MHz is 6 meters, and 146.52 MHz is 2 meters. Any amateur with a Technician license or higher may try to contact the International Space Station on the VHF bands. SSB phone is allowed in at least some segment of every amateur band above 50 MHz. In segments where the Amateur Radio Service is a secondary user, expect to find non-amateur stations working there, and remember that you must not interfere with them. Finally, never park your dial exactly on the edge of a band or sub-band: your signal has width, and its edges can spill past the line even when the number on the display looks legal.

The conduct rules have fine print the exam loves. Willful or malicious interference is prohibited, full stop, and so is any indecent or obscene language. Your international contacts are for communications incidental to the purposes of the service and remarks of a personal character, and a few countries are simply off limits: any country whose administration has notified the ITU that it objects to amateur communications. Broadcasting is defined as transmissions intended for reception by the general public, and one-way transmissions for broadcasting are prohibited. The famous no-music rule has exactly one crack in it: music sent with a phone emission is permitted when it is incidental to an authorized retransmission of manned spacecraft communications. Coded messages meant to obscure meaning are allowed only in one corner, sending control commands to space stations or to model craft. You may use your station to tell other amateurs about your own amateur equipment for sale or trade, as long as it is your gear and not a regular business. Helping with broadcasting, program production, or news gathering is allowed only when the communication is directly related to the immediate safety of human life or the protection of property and no other means is available. Even test transmissions must identify your station. And the single case where a transmission needs no identification at all is sending control signals to model craft.

The control operator rules go deeper than "you are responsible." A station may never transmit without a control operator; there is no unattended manual exception. The station licensee is the one who designates who the control operator is, and when the operator and the licensee are different people, both of them answer for the station's proper operation. The privileges on the air are set by the license class of the control operator, not by who owns the equipment. The control point is the place where the control operator function is performed. Part 97 sums the job up this way: the control operator is the amateur the licensee designates to be responsible for the station's transmissions and for following the FCC rules. Control comes in flavors. Repeater operation is the classic example of automatic control. Remote control is the other kind: any amateur station may be remotely controlled, and running your station over the internet is the standard example. For satellites, the rule is simple: anyone who is allowed to transmit on the satellite's uplink frequency may be the control operator of a station working through it.

Identification and messages for others have their own details. Identify in English. A station transmitting phone may send its call sign with either a CW or a phone emission, and adding a self-assigned indicator, like the suffixes hams use for a brand-new upgrade or portable operating, is acceptable. Passing a message for someone else is third-party communication: a message from one control operator to another station's control operator on behalf of a third person. If an unlicensed person wants to talk through your station to a foreign amateur, that is only allowed when the foreign station's country has a third-party agreement with the United States. A repeater station, by definition, simultaneously retransmits the signal of another amateur station on a different channel. If a repeater happens to retransmit something that breaks the rules, the blame lands on the control operator of the station that originated the transmission, not on the repeater's owner. And for identification itself, the rules encourage using a phonetic alphabet so your call sign is understood the first time.

Key facts:

• A Technician license is good for 10 years, with a 2 year grace period to renew after it expires
• Technicians get all VHF and UHF privileges, plus parts of the 80, 40, 15, and 10 meter HF bands
• Another person may use your station only if a licensed control operator is present and responsible
• Never transmit on a frequency your license class does not allow, even if someone invites you to
• Technician HF power limit is 200 watts PEP; above 30 MHz it is 1,500 watts PEP
• Technician phone on HF is 10 meters only, 28.300 to 28.500 MHz; the CW-only slices are 50.0 to 50.1 and 144.0 to 144.1 MHz
• Your license is real when it appears in the FCC ULS database, and you may transmit as soon as it does
• An expired license in its grace period may be renewed but may not be transmitted on until the renewal lands
• The control operator's license class sets the station's privileges, and the licensee picks the control operator
• Music is allowed only when it rides along with an authorized retransmission of manned spacecraft communications

Start T1 on the learning path

Good operating starts with listening. Before calling, listen on the frequency and ask, "Is this frequency in use?" A CQ is a call to any station: say CQ and your call sign, using the phonetic alphabet so letters stay clear through noise (Alpha, Bravo, Charlie, and so on). Most local talk goes through repeaters: a repeater listens on one frequency and retransmits on another, so your radio transmits on the repeater's input frequency and listens on its output. The split between them is the offset, 600 kHz on the 2 meter band. Many repeaters also need a CTCSS tone, a quiet tone your radio sends to open the repeater up. Simplex means both stations talk and listen on the same frequency. If you hear emergency traffic, stop and give it the frequency. Hams also use short Q signals: QRM means interference from other stations, QTH means location, and QRP means low power.

Two numbers belong in your head next to the 600 kHz offset you already know. The national calling frequency for FM simplex on 2 meters is 146.520 MHz; it is where you call when you want any station listening, and where a lot of hams monitor. And the 600 kHz split is a 2 meter habit: on the 70 centimeter band the common repeater offset is plus or minus 5 MHz. The offset itself, on any band, is just the difference between the repeater's transmit frequency and its receive frequency.

Calling has a choreography, and the exam checks that you know the steps. To call a station you already know on a repeater, say that station's call sign first, then your own. Answering someone else's CQ works the same way: their call sign, then yours. When you are the one calling CQ away from a repeater, repeat "CQ" a few times, then say "this is" and your call sign, then stop and listen; repeat as needed. If you are simply available on a repeater and willing to talk, say your call sign and the word "listening." That one word tells everyone monitoring that a contact is welcome. One more agreement sits on top of the FCC rules: band plans. A band plan is a voluntary guideline, worked out by hams themselves, that says which parts of a band are used for which modes and activities. The FCC does not enforce it, but following it is what makes the bands usable. Band plans are also why simplex channels exist on VHF and UHF: so stations close enough to hear each other can talk directly instead of tying up a repeater.

Your radio has a few controls the exam expects you to understand. The squelch mutes the receiver's audio whenever no signal is present, so you are not listening to static between transmissions. The reverse function flips your radio to listen on the repeater's input frequency, which tells you whether the other station is close enough to reach you directly. DTMF, the touch-tone sounds, is made of two audio tones sent at the same time, and it is how hams command repeaters and linked nodes. Digital repeaters organize people with talkgroups: an identifier for a group, which you join by programming the group's ID or code into your radio. On DMR, the color code works like a CTCSS tone for the digital world; it is an access code that must be programmed into your transmitter for that specific repeater. A linked repeater network goes further and ties repeaters together so that what one repeater hears is retransmitted by all of them.

Troubleshooting and courtesy fill out the rest. If you can hear a repeater clearly but cannot get into it, work the short list of usual causes: the wrong access tone, the wrong offset, or your signal simply not reaching its receiver from where you are. If your FM audio drops out on the loud parts of your voice, you are talking too loudly; back off the microphone. And when two stations end up interfering with each other on the same frequency, the rule of the road is to negotiate continued use of the frequency like adults, not to shout over each other. Add one Q signal to the three you know: QSY means you are changing frequency.

The last block is nets and formal traffic, the organized side of ham radio. Understand first that the FCC rules always apply, in nets, in contests, and in emergencies alike; they never switch off. A net is run by a Net Control Station, who calls the net to order and directs the communications between stations checking in. The standing practice is discipline: unless you are reporting an emergency, you transmit only when the Net Control Station directs you to. The messages a net passes are called traffic, which means formal messages exchanged between net stations. A formal message has a preamble holding the information needed to track it, and a "check," which is the count of the words, or word equivalents, in the text of the message. Unusual words get spelled out with the phonetic alphabet so they arrive exactly right. Winlink is the bridge between this world and ordinary email: it relays messages using email addresses built on amateur call signs. Two volunteer organizations show up in this section. ARES, the Amateur Radio Emergency Service, is made of licensed amateurs who have registered their qualifications and equipment for communications duty in the public service. RACES is different and stricter: it is the Part 97 service for civil defense communications during national emergencies, and joining it requires certification by a civil defense agency. One safety valve sits above all of it: the only time any operator may use frequencies outside their own license class privileges is a situation involving the immediate safety of human life or the protection of property.

Key facts:

• Always listen first, and keep transmissions short on repeaters so others can get in
• Voice signal reports are RST: Readability 1 to 5, Strength 1 to 9. A perfect report is 59
• On repeaters, pause between transmissions so the repeater can reset and others can join or call for help
• Your call sign in phonetics beats mumbled letters every time
• 146.520 MHz is the 2 meter FM simplex calling frequency; the 70 centimeter repeater offset is plus or minus 5 MHz
• Call a station by saying their call sign first, then yours; answer a CQ the same way
• QSY means changing frequency; a band plan is a voluntary agreement, not an FCC rule
• In a net, transmit only when the Net Control Station directs you, unless it is an emergency
• RACES needs civil defense certification; ARES is the registered volunteer service

Start T2 on the learning path

Radio waves reach other stations two main ways. Ground wave and line of sight are direct: VHF and UHF signals mostly travel straight, bend only a little, and stop at the horizon, which is why repeaters live on hilltops and tall towers. The second way is the sky wave: HF signals can bounce off the ionosphere, a set of layers high above the earth that the sun charges up during the day. That bounce is why HF can reach other continents. Sunspots matter: more sunspots usually mean a stronger ionosphere and better long distance HF, and the sunspot cycle runs about 11 years. Night changes everything, because some layers fade after dark, so lower HF bands open up at night while higher ones close down. VHF has its own surprises: sporadic E can bounce 6 and 2 meter signals hundreds of miles for a few hours, and tropospheric ducting can carry UHF signals far along weather fronts.

Before the paths, know the wave itself. A radio wave is two fields traveling together, an electric field and a magnetic field, set at right angles to each other. Which way the wave is polarized is set by the orientation of its electric field: electric field vertical, wave vertically polarized, and the same for horizontal. Every radio wave in free space moves at the speed of light, about 300,000,000 meters per second, and frequency does not change that; a 2 meter signal and an HF signal leave the antenna at exactly the same speed. The bands are named two ways at once, by frequency range and by their rough wavelength in meters, which is where names like the 2 meter band come from. The ranges are worth memorizing cold: HF runs 3 to 30 MHz, VHF runs 30 to 300 MHz, and UHF runs 300 to 3,000 MHz.

Most of the strange behavior of local signals comes from one idea: multipath. Your signal rarely takes a single road to the other station. It bounces off buildings, hills, and vehicles, and the copies arrive at slightly different times. Where the copies add up, the signal is strong; where they cancel, it drops into a hole. That is why a VHF signal can swing from full strength to nothing when the antenna moves only a few feet, and why a mobile signal flutters rapidly as you drive, an effect hams call picket fencing. Multipath also scrambles digital signals, raising the error rate on data. Two more local effects matter. Vegetation soaks up UHF and microwave signals, so trees between you and a weak station genuinely hurt. And polarization is not a detail: on a line-of-sight path, a vertical antenna talking to a horizontal one loses most of the signal to cross-polarization. That is why serious long-distance CW and SSB work on VHF and UHF uses horizontal polarization on both ends. Ionospheric signals play by different rules: they come back down elliptically polarized, twisted on the way, so either a vertical or a horizontal antenna can work for them. When buildings block your direct path to a repeater, a directional antenna gives you one more trick: aim at a surface that can reflect your signal around the obstruction and into the repeater. Rain and fog, by the way, barely touch 10 meter and 6 meter signals, but precipitation does eat into range up at microwave frequencies.

Now the horizon tricks, the ways VHF and UHF sometimes travel farther than they should. First, your radio horizon is already a little farther than your visual horizon, because the atmosphere refracts radio waves and bends them slightly around the curve of the earth. Past that, UHF signals are rarely heard, because the ionosphere almost never bends UHF back down the way it does HF. A sharp ridge or building edge can help through knife-edge diffraction, which spills a signal over an obstruction into the shadow behind it. The aurora can act as a rough mirror too, but signals reflected from it come back distorted with a raspy, buzzing sound that is unmistakable. Tropospheric ducting, which you already met, is caused by temperature inversions, layers where warm air sits on top of cool air and traps the signal between them; that is the mechanism that regularly carries VHF and UHF around 300 miles. For meteor scatter, where your signal bounces off the ionized trail of a burning meteor for a second or two at a time, the best band is 6 meters. And the F region rewards patience at the top of the sunspot cycle: the best long-distance 10 meter time runs from dawn to shortly after sunset during high sunspot activity, and at the cycle's peak even 6 meters can open for true long-distance work through the F region, which almost never happens in quiet years.

Key facts:

• VHF and UHF are local, line of sight bands. Height beats power
• HF long distance depends on the ionosphere, the sun, and the time of day
• A signal that is strong all day and gone at night (or the reverse) is normal propagation, not broken gear
• Weather barely affects HF, but it can stretch VHF and UHF through ducting
• HF is 3 to 30 MHz, VHF is 30 to 300 MHz, UHF is 300 to 3,000 MHz; all of them travel at the speed of light
• Multipath is signals arriving by several paths and canceling or reinforcing; on a moving station it sounds like picket fencing
• Polarization follows the electric field; crossed polarizations cost you most of a line-of-sight signal
• Ducting is caused by temperature inversions; meteor scatter belongs on 6 meters

Start T3 on the learning path

This subject is the everyday craft of running a station well. Set up neatly and safely, with short, tidy cables and everything grounded together. Use the minimum power that does the job: it is the rule, it is polite, and it prevents interference. When something sounds wrong, hunt the cause in order: check your own antenna connections and feed line first, because most interference problems start at home. A dummy load lets you test a transmitter without putting a signal on the air; it turns radio energy into heat instead of radiating it. Test gear earns its keep: an SWR meter watches your antenna match, and an antenna analyzer shows where an antenna is resonant. If you run digital modes or amplifiers, watch your signal and your equipment heat, and keep a clean, narrow signal so you are a good neighbor on the band.

Power comes first, because a station that is starved for power misbehaves in ways that look like radio problems. A typical 50 watt mobile FM rig wants 13.8 volts at about 12 amperes, so the supply feeding it needs that much headroom. The wires between the supply and the radio matter as much as the supply: keep them short and heavy-gauge, because a long thin wire drops voltage every time you key up, and the radio feels it exactly when it is working hardest. In a vehicle, the negative return lead goes to the 12-volt battery's chassis ground point, not just any convenient bolt. Battery math is one division problem: take the battery's ampere-hour rating and divide by your equipment's average current draw, and you have roughly how many hours it will run your station. For RF grounding and bonding, the conductor of choice is flat copper strap. RF travels on the surface of a conductor, and a wide flat strap gives it far more surface than a round wire of the same weight.

Meters and computers plug into a station in specific places. An RF power meter belongs in the feed line, between the transmitter and the antenna, where it can see what actually leaves the station. When you shop for an accessory SWR meter, check two ratings before anything else: the frequencies it covers and the power levels it can handle, since a meter built for HF will not tell the truth on UHF. Digital modes turn your computer into part of the radio. The connection between them carries three things: receive audio, transmit audio, and a keying signal that tells the radio when to transmit. In practice that means cables like the computer's line-in fed from the transceiver's speaker connector, and the computer's audio out feeding the radio's mic or data input, which is exactly how an FT8 station is wired. A digital hotspot is the small box that gives radios near it a doorway into a digital voice or data network. And one old tool survives from the CW era: an electronic keyer, a device that helps you send clean, even Morse code by hand.

The front-panel controls are on the exam because using them wrong is how beginners sound bad. You set the operating frequency with the keypad or the VFO knob, and the scanning function sweeps a range of frequencies for you, stopping where it finds activity. Squelch cuts both ways: set the threshold too high and weak stations vanish, so to hear a weak FM signal you turn the squelch down until the receiver audio stays on all the time and you listen through the noise. An FM signal received slightly off frequency comes out distorted, which is a tuning problem, not a broken radio. On SSB the equivalent fix is the RIT or Clarifier: when the station answering you sounds pitched too high or too low, that control fine-tunes your receive frequency without moving your transmit frequency. Receiver filter bandwidth is your main weapon against noise and nearby signals: choose the filter that matches the mode you are using, and the unwanted energy outside that width never reaches your ears. For SSB voice, the bandwidth with the best signal-to-noise ratio is about 2,400 Hz.

Digital voice radios add one more layer: they are programmed, not just tuned. A DMR radio loads a configuration file called a code plug, which holds the repeaters, channels, and talkgroups the radio knows about. To select a particular group of stations on DMR, you enter the group's identification code. D-STAR has a hard rule of its own: before the radio will transmit, your call sign must be programmed into it, because the network routes by call sign.

Key facts:

• Most interference is caused by loose connections, bad coax, or overdriven audio. Check your own station first
• Test into a dummy load, not on a busy frequency
• Minimum power needed is both an FCC rule and good manners
• If your audio sounds distorted, turn the microphone gain down before anything else
• A 50 watt mobile rig wants about 13.8 volts at 12 amps; short, heavy power leads fight voltage drop
• Battery hours equal ampere-hours divided by average current draw
• Bond RF grounds with flat copper strap; put the RF power meter in the feed line
• SSB sounds pitched wrong? Reach for the RIT or Clarifier, not the main tuning knob
• A code plug is the setup file inside a DMR radio; D-STAR needs your call sign programmed before it transmits

Start T4 on the learning path

Everything electrical in this exam comes from a few ideas. Voltage is electrical pressure, measured in volts. Current is the flow itself, measured in amps. Resistance, in ohms, is anything that pushes back against the flow. Ohm's law ties them together: volts equal amps times ohms (V = I x R), and from that one rule you can solve for any of the three. Power is volts times amps (P = V x I), measured in watts. Frequency counts how many times an alternating signal swings per second, in hertz; as frequency rises, wavelength shrinks, and in meters the wavelength is about 300 divided by the frequency in megahertz. Decibels compare powers: 3 dB is about double, 10 dB is ten times. Resistors in series add up. Resistors in parallel give current more paths, so the total is less than the smallest one.

Two short ideas finish the picture of what electricity is doing inside a wire. Metals conduct so well because their atoms hold their outer electrons loosely; a metal is full of free electrons ready to move the moment voltage pushes them, and that moving crowd is the current. Materials at the other extreme, like glass, hold their electrons tight, which is what makes them good insulators to wrap around the conductors.

Two prefixes complete the set you already know. Beyond mega comes giga, one billion: 2,425 MHz is the same thing as 2.425 GHz. At the tiny end, below micro sits pico, one trillionth: a million picofarads add up to a single microfarad. Radio parts live at these scales, so the full ladder, pico, micro, milli, one, kilo, mega, giga, is worth knowing in order.

Two energy-storage ideas get names here that the components lesson will use. Capacitance is the ability to store energy in an electric field, and it is measured in farads. Inductance is the ability to store energy in a magnetic field, and it is measured in henries. One more opposition word joins resistance: impedance is the opposition to alternating current flow, the AC cousin of resistance, and it is measured in ohms as well.

Series and parallel circuits each keep one thing the same everywhere. Wire parts in series and the same current flows through every one of them, like the same water through a single pipe; that is why series resistances simply add. Wire parts in parallel and every branch sees the same voltage across it, while the current splits between the paths; that is why parallel resistance always comes out less than the smallest single resistor.

Key facts:

• Memorize two formulas and most math answers fall out: V = I x R and P = V x I
• Wavelength in meters is about 300 / frequency in MHz. Higher frequency, shorter antenna
• 3 dB doubles power, -3 dB halves it, 10 dB is 10 times
• Metric prefixes show up constantly: milli is a thousandth, micro a millionth, kilo a thousand, mega a million
• Metals conduct because they are full of free electrons; glass is a classic insulator
• Pico is a trillionth and giga is a billion; capacitance is measured in farads, inductance in henries
• Impedance is opposition to AC current, measured in ohms
• Series circuits share one current everywhere; parallel circuits share one voltage everywhere

Start T5 on the learning path

Circuits are built from a small family of parts, and the exam wants you to know what each one does and what it looks like on a schematic drawing. A resistor limits current and drops voltage. A capacitor stores energy in an electric field, blocks direct current, and lets alternating current pass. An inductor, a coil of wire, stores energy in a magnetic field and resists changes in current. A diode lets current flow one way only, and an LED is a diode that makes light. A transistor is a switch and amplifier controlled by a small current or voltage. A fuse protects a circuit by melting open when current runs too high. Batteries turn stored chemical energy into electricity. Being able to read the schematic symbols for these parts is half of this section, so picture each symbol as you learn the part.

Meet the adjustable resistor first. A potentiometer is a resistor you can turn, and turning it changes the resistance in the circuit. It is the component behind almost every volume knob ever made: the knob sweeps a contact along a resistive track, and the circuit gets more or less resistance as you turn. Switches have a naming system based on poles and throws. A single-pole single-throw switch is a plain on-off switch for one circuit. A single-pole double-throw switch, SPDT, connects one circuit to one of two others, choosing which way the signal goes, like a railroad switch for electrons.

Batteries are not all the same inside. Nickel-cadmium, nickel-metal hydride, and lithium-ion cells are built to be recharged hundreds of times. Plain carbon-zinc cells are the disposable kind; when one is dead, it is dead, and trying to recharge it is asking for a leak or a burst.

The diode family has details worth knowing. A diode's two leads have names: the anode and the cathode, and on most real diodes the cathode end is marked with a stripe printed on the package. Current flowing the forward way produces a small forward voltage drop, and that drop is not the same for every diode; some types drop less than others, which is one reason different diodes exist. An LED lights for a simple reason: forward current is flowing through it. No forward current, no light. Transistors split into two families. A bipolar junction transistor is three regions of semiconductor material in a sandwich, with three leads named the emitter, the base, and the collector; a small base current controls a much larger collector current. A field-effect transistor, FET for short, has leads named the gate, the drain, and the source, and it is controlled by voltage on the gate instead of current. Either way, the point of the device is gain: how much bigger the output signal is than the input that controlled it. Gain is the whole reason amplifiers exist.

A whole toolbox of supporting parts rounds out a real station. A rectifier changes alternating current into a varying direct current, which is the first thing every power supply does to wall power. A transformer changes AC voltage from one level to another, stepping 120 volt house current down to the lower AC voltage a circuit wants, before the rectifier takes over. A regulator then holds the supply's output voltage steady at the amount the circuit needs. A relay is a switch flipped by electricity instead of by your finger, so a small signal can control a big circuit. A meter displays an electrical quantity as a number you can read. An integrated circuit packs several semiconductors and other components into a single package, whole circuits shrunk onto one chip. And shielded wire wraps its conductor in a protective braid to keep unwanted signals from coupling into the wire, or leaking out of it.

One partnership of parts matters so much it gets its own name. Put a capacitor together with an inductor and you have a resonant circuit, also called a tuned circuit, whether the two are wired in series or in parallel. Each one stores energy in its own way, field and magnetism trading the energy back and forth, and at one frequency the pair resonates. Tuners, filters, and oscillators all live on this idea.

A schematic is the diagram that draws a circuit with standard symbols, and what it shows you accurately is how the components connect. Learn the cast of the three exam figures and you have learned the symbol system. In figure T-1, component 1 is a resistor, 2 is a transistor (its job there is to control the flow of current), 3 is a lamp, and 4 is a battery. In figure T-2, component 3 is a single-pole single-throw switch, 4 is a transformer, 6 is a capacitor, 8 is a light emitting diode, and 9 is a variable resistor. In figure T-3, component 3 is a variable inductor and 4 is an antenna. When you drill the figure questions, do not guess from memory of this list; picture the symbol: the zigzag is resistance, the two plates are a capacitor, the coil is an inductor, and an arrow on a symbol means that part can be adjusted.

Key facts:

• Capacitor: blocks DC, passes AC, stores energy in an electric field
• Inductor: a coil; stores energy in a magnetic field; opposes changes in current
• Diode: one way street for current. LED: a diode that lights
• Fuse: the part that sacrifices itself to protect everything else
• A potentiometer is an adjustable resistor; it is the part behind a volume control
• Diode leads are anode and cathode, and the cathode usually wears a stripe; bipolar transistor leads are emitter, base, collector; FET leads are gate, drain, source
• Carbon-zinc batteries cannot be recharged; nickel and lithium chemistries can
• A capacitor plus an inductor makes a resonant (tuned) circuit, in series or in parallel
• A rectifier makes DC from AC, a regulator holds voltage steady, a relay is a switch worked by electricity

Start T6 on the learning path

A ham station is boxes connected in a chain. A power supply turns house AC into the 12 volt DC most radios eat. A transceiver is a transmitter and receiver in one box. Between the radio and the antenna you may find filters that keep your signal clean, an amplifier that adds power, an antenna tuner that helps the radio accept the antenna, and meters that watch it all. When something breaks, troubleshoot in order and change one thing at a time: Is it plugged in and powered? Are the connectors tight and on the right jacks? Are the settings right for the band and mode? A multimeter is the basic tool: it measures voltage, resistance, and current, and you always check resistance only with the power off. Soldered joints should be shiny and smooth; a dull, grainy cold solder joint is a failure waiting to happen.

A receiver is judged by two words that sound alike and mean different things. Sensitivity is its ability to detect the presence of a signal at all, to pull a whisper out of the noise. Selectivity is its ability to discriminate between multiple signals, to hear the one station and reject the one right next to it. Inside the box, a few circuits do the frequency work. An oscillator generates a signal at one specific frequency, and the Variable Frequency Oscillator, the VFO, is the one that sets your receive and transmit frequency as you tune. A mixer takes a signal at one frequency and converts it to another, which is how radios move signals around internally. Modulation is the act of combining your speech with the RF carrier so the carrier carries it. A transverter is an add-on box that converts your transceiver's input and output to a band the radio does not cover on its own. The PTT input is the switch line: ground it, and the transceiver flips from receive to transmit, which is what your microphone button and your digital interface both do. On amplifiers that offer an SSB/CW switch, that switch sets the amplifier up for proper operation in the mode you picked. And the reason a solid-state rig sometimes shows low output is self-defense: as SWR climbs, the transmitter reduces its power to protect its RF output transistors, so low output on a bad antenna match is the radio saving itself.

Interference work is mostly manners plus filters. If you are told your FM signal is over-deviating, the cure is embarrassingly simple: talk farther away from the microphone. If your voice through a repeater comes out distorted, remember the causes are ordinary ones, including your battery, your location, and your audio settings, and check them before blaming the repeater. A broadcast radio that hears your amateur transmissions is usually suffering from overload: it cannot reject a strong signal from outside its own band. The fix that helps a neighbor's set is a filter at the antenna input of the affected receiver, which blocks your signal before it gets in. Running the problem the other direction, a strong commercial FM station can swamp a 2 meter receiver, and the cure there is a band-reject filter that notches out the offender. If RF is getting back into your own audio and garbling your voice, a clip-on ferrite choke on the microphone cable can stop the feedback and clean the transmission up. When a neighbor complains, the first move is always at home: prove your own station is clean by confirming your transmissions do not bother your own radio or television tuned to the same channel. For cable TV interference blamed on your station, the first step is checking that every TV feed line coax connector is installed properly, because a loose shield connection is the usual doorway. And when the interference runs the other way, from a neighbor's gadget into your station, the playbook is cooperation: find the device together, be polite about it, and solve it like neighbors, because the rules and your reputation both reward that. Interference itself comes from a short list of causes worth knowing by name: fundamental overload, harmonics, and spurious emissions.

Test gear has specifics the exam checks one by one. A dummy load is a 50-ohm non-inductive resistor mounted on a heat sink, built to swallow your transmitter's power as heat so you can test without radiating, which is its whole purpose. SWR can be measured with a directional wattmeter as well as a dedicated SWR meter. Power that a feed line loses does not vanish; it turns into heat inside the cable. Coax dies by water: moisture contamination is the classic cause of cable failure, which is why the outer jacket needs to resist ultraviolet light, since sun-rotted jackets crack and let the water in. Between cable types, foam-dielectric coax loses less signal per foot than solid-dielectric coax.

The meter bench has connection rules that are pure exam gold. A voltmeter, the instrument for electric potential, always connects in parallel, across the component. A meter measuring current, an ammeter or a multimeter on its current setting, always connects in series, in line with the component, so the current flows through the meter. An ohmmeter works by applying a small current of its own and measuring the voltage that results, then doing the division for you; that is also why a big discharged capacitor fools it, showing a resistance reading that climbs with time as the capacitor charges from the meter's own current. Two ways to hurt a meter: try to measure voltage while it is set to resistance, which can damage it, and measure resistance on a live circuit, which you already know never to do. At the soldering bench, use rosin-core solder only; acid-core solder, made for plumbing, corrodes electronic joints and should never touch radio work.

Key facts:

• Troubleshoot in a fixed order: power, connections, settings, then parts
• Measure resistance and continuity only on unpowered circuits
• A receiver with no signals at all: check the antenna connection before blaming the radio
• Keep a simple station log of changes. The last thing you touched is the first suspect
• Sensitivity hears weak signals; selectivity separates close ones; a mixer moves a signal to a new frequency
• Over-deviating on FM? Talk farther from the microphone
• Voltmeters go in parallel, current meters go in series, and an ohmmeter pushes its own small current through the part
• A dummy load is a 50-ohm non-inductive resistor on a heat sink; lost feed line power becomes heat
• Never use acid-core solder on electronics

Start T7 on the learning path

Every transmission takes up elbow room on the band, called bandwidth, and the exam expects you to know the order of things: plain Morse code (CW) is the narrowest, a single sideband voice signal is a few kilohertz wide, FM voice is wider still, and fast scan television is the widest of the common modes. Emission labels name the shape: phone means voice, image means pictures and TV, data means digital modes, and CW means Morse. Keeping your signal clean is a legal duty and a courtesy: too much microphone gain or an overdriven amplifier makes splatter, extra signals on nearby frequencies, and harmonics, which are copies of your signal at multiples of your frequency. Digital modes are often run at reduced power because they transmit steadily and heat the radio; that steady load is called duty cycle.

Put numbers on the bandwidth ladder you already know, because the exam asks for them. A CW signal needs only about 150 Hz. An SSB voice signal takes about 3 kHz. An FM voice signal on a VHF repeater spreads across 10 to 15 kHz. And an AM fast-scan television signal eats about 6 MHz, thousands of times wider than the CW signal, which is why TV lives where there is room for it. Two family facts ride along: single sideband is a form of amplitude modulation with one sideband kept and the carrier and other sideband thrown away, and the sideband everyone uses on 10 meters and on the VHF and UHF bands is the upper sideband. FM has one built-in weakness compared with SSB: when two FM signals land on the same frequency, you hear only one of them, the stronger one, because the receiver locks onto it. On SSB the two signals mix and both can be copied. Packet radio on VHF usually rides on FM or PM, and weak-signal operators doing long-distance voice work on VHF and UHF choose SSB precisely because its narrow bandwidth concentrates the power.

Satellites get a whole block of the exam, so they get a real introduction here. An amateur satellite is a repeater in orbit, and almost everything about working one follows from that. Its beacon is a transmission that carries telemetry, the satellite's health and status information, and anyone at all may listen to it; receiving telemetry needs no license. Working through a satellite has a courtesy problem built in: the transponder hears everybody at once, so if your uplink power is excessive, your signal hogs the satellite and blocks access by other users. The self-check is elegant: on a linear transponder, listen to your own signal coming back on the downlink and compare it with the beacon. If your signal is about the same strength as the beacon, your power is right. None of this works without knowing where the satellite is. Tracking programs do that job: you feed them the Keplerian elements, the numbers that describe the satellite's orbit, and they hand you back maps, antenna bearings, and the times of the next passes. Two motion effects show up in the questions. Doppler shift is the change in the signal's frequency caused by the relative motion between the satellite and your station, the same reason a passing siren changes pitch; you will tune to follow it during a pass. Spin fading is the flutter caused by the satellite rotating and swinging its antennas around as it tumbles or spins. The mode label U/V tells you the bands: the uplink is in the 70 centimeter band (U) and the downlink is in the 2 meter band (V). Most amateur satellites live in LEO, low earth orbit, circling the planet in roughly 100 minutes, which is why passes are short and frequent. And the modes they carry are the familiar ones: SSB, CW, and FM all fly.

The activity words are a vocabulary set of their own. Radio direction finding is how hams locate a noise source, a jammer, or a hidden transmitter, and the tool of the sport is a directional antenna. Contesting is the sport of contacting as many stations as possible inside a set period, and good contest practice is brevity: send only the minimum information needed for identification and the exchange. Your grid locator is the short letter-and-number code that names the square of the map you are operating from, the way operators swap locations without addresses. Then comes the internet family. VoIP is voice delivered over the internet by digital techniques. IRLP, the Internet Radio Linking Project, connects amateur systems like repeaters through the internet, and you reach its nodes over the air by sending DTMF tones. EchoLink is the protocol that lets a station come in through the internet and transmit through a repeater without a radio starting the contact; before you use it, you must register your call sign and provide proof that you are licensed. A station that connects other amateur stations to the internet is called a gateway.

The digital modes each have a one-line identity, and the exam tests exactly those lines. FT8 is the weak-signal champion, designed to complete contacts at signal-to-noise ratios where voice would be hopeless. PSK means Phase Shift Keying, a mode that encodes data in the phase of the signal. APRS is the position and data system: it can carry position reports, weather readings, and short messages, and its classic use is real-time tactical communication on a map that shows where every station is. Packet radio transmissions are little envelopes that include addressing and error-check information along with the message. ARQ is the polite error fixer: the receiving station detects errors and asks for a retransmission. DMR fits two separate digital voice conversations onto one 12.5 kHz repeater channel by time-multiplexing, slicing time between them. NTSC names the analog fast-scan color TV signal. The WSJT-X software suite is the toolbox for the extreme weak-signal sports, including bouncing signals off the moon and off meteor trails. And a mesh network is a data network built from commercial Wi-Fi equipment running modified firmware, ham ingenuity on grocery-store hardware.

Key facts:

• Narrowest to widest: CW, then SSB voice, then FM, then television
• Splatter and harmonics come from overdriving. Back the gain down
• Your signal must stay inside the band and inside your license privileges, including its edges
• Steady digital transmissions heat radios. Lower power protects the finals
• Bandwidth numbers: CW about 150 Hz, SSB about 3 kHz, FM voice 10 to 15 kHz, fast-scan TV about 6 MHz
• SSB is a kind of AM; use the upper sideband on 10 meters, VHF, and UHF
• A satellite beacon reports the satellite's health and status, and anyone may listen
• Match your downlink strength to the beacon and your uplink power is right; U/V means up on 70 cm, down on 2 meters
• FT8 works in noise that buries voice; ARQ errors get a polite request to send it again

Start T8 on the learning path

Ask experienced hams and they will tell you: the antenna matters more than the radio. The workhorse is the dipole, two equal legs stretched out from a center feed point. Each leg is about a quarter wavelength, and for a dipole in feet the full length is about 468 divided by the frequency in megahertz. A vertical antenna stands up and usually needs radials or a ground system under it. A Yagi beam aims your signal one direction and adds gain, like a flashlight reflector. Coax feed line carries the signal from radio to antenna, and every foot of it loses a little signal; the loss grows with frequency and with cheaper, thinner cable. SWR, standing wave ratio, grades the match between feed line and antenna: 1 to 1 is perfect, and a high SWR means power is bouncing back instead of radiating. Radios and antennas also have polarization: most repeater work is vertical, most HF is horizontal, and matching the other station's polarization keeps signals strong. Above all, never let any antenna touch or fall across a power line.

An antenna has a shape to its voice. A half-wave dipole does not spray signal equally in all directions: it radiates strongest broadside, off its flat sides, and weakest off its ends, which is worth knowing before you string one up pointing the wrong way. Gain, the word every antenna advertisement shouts, has a precise meaning: it is the increase in signal strength in a specified direction compared with a reference antenna. A beam does not create power; it concentrates the power you have into the direction you point it, like the reflector behind a flashlight bulb. Size trades against convenience everywhere. The short flexible antenna on a handheld is easy to carry but inefficient next to a full-size quarter-wave antenna, and using that handheld inside a car costs you even more, because the metal body shields the signal. On 2 meters, the classic mobile answer is a vertical about 19 inches long, which is no accident: that is a resonant quarter wavelength on the band. Step up to a 5/8-wavelength whip and you gain more signal than the quarter wave gives you. When an antenna is physically too short for the band, loading fixes it electrically: inserting inductors into the radiating elements makes the antenna act longer than it is. One adjustment fact ties the whole subject together: shortening a dipole raises its resonant frequency, which is exactly why the old advice says to cut a dipole a little long and then trim it down to resonance. And remember that an antenna's polarization is described by the orientation of its electric field, the rule behind the vertical and horizontal choices you already know.

Feed lines have their own fact set. Almost all amateur coax is 50-ohm cable, and coax conquered the hobby because it is easy to use and asks for almost no special installation care. An antenna tuner's real job, stated properly, is to match the impedance of the antenna system to the output impedance of the transceiver, so the radio sees the 50 ohms it wants. Loss creeps in from three directions at once: the diameter of the cable, its length, and the frequency you run through it. That is why RG-213, the thicker cable, loses less than skinny RG-58 at the same frequency, and why the lowest-loss feed line of all is air-insulated hardline, the rigid pipe-like line on big towers. Connectors follow one simple rule: the PL-259 is the everyday connector at HF and VHF, but above 400 MHz the Type N is the right tool for the job. Whatever connector goes outdoors gets carefully taped and sealed against the weather, every type, no exceptions. And when your SWR readings start jumping around erratically, do not blame the antenna design: hunt for a loose connection in the antenna or the feed line.

Key facts:

• Dipole length in feet is about 468 / MHz. Cut a little long, then trim for low SWR
• High SWR: check for damaged coax, water in connectors, and wrong antenna length
• Thin coax is fine for short runs; long runs and high frequencies want better cable
• An antenna at a safe height that stays up beats a perfect antenna that falls on a power line
• A dipole shouts broadside and whispers off its ends; gain means strength in one direction versus a reference antenna
• Almost all ham coax is 50 ohms; a tuner matches the antenna system to the radio's 50 ohms
• A 19 inch whip is a quarter wave on 2 meters; a 5/8-wave whip beats a quarter wave for gain
• RG-213 loses less than RG-58, hardline loses least of all; use Type N above 400 MHz
• SWR jumping around erratically usually means a loose connection somewhere

Start T9 on the learning path

Radio is safe when you respect two things: electricity and height. Wires and towers kill people every year, usually through contact with power lines, so before any antenna work, look up and plan where everything could fall; nothing you put up may ever be able to touch a power line. Towers get climbed only with proper gear, a helper on the ground, and no work in wind or storms. Indoors, remember that power supply capacitors can hold a painful or deadly charge long after switch off, and big batteries can deliver enormous current if shorted, enough to melt tools and start fires. Radio frequency energy itself is a safety topic: the FCC sets RF exposure limits, and your duty is to evaluate your station, keep people a sensible distance from antennas while transmitting, and never look into or touch an antenna that is live. Lightning protection means grounding feed lines where they enter the house and disconnecting when storms roll in.

House wiring has a color code worth memorizing before you ever open an outlet. In a standard three-wire cable in the United States, the black wire is hot, the white wire is neutral, and green or bare copper is ground. Fuses and circuit breakers belong in series with the hot wire only, because that is the wire carrying the danger. A fuse has one job: when current runs past its rating, it opens and removes power before something melts. That is why you never put a bigger fuse in to stop one from blowing. A 20 amp fuse standing guard over a circuit built for 5 amps will happily let through enough current to heat wires and start a fire.

Electricity hurts the body three ways at once. It heats tissue the way a heating element heats water. It scrambles the tiny electrical signals your nerves and cells run on. And it forces muscles to contract on their own, which is the cruelest part: a hand gripping a live wire may be unable to let go. Guard against it at your own station with insulated wiring and tools, grounded three-wire plugs, and ground fault protection that cuts power the moment current leaks where it should not go. And when you measure high voltage, remember that the meter and its test leads have voltage ratings too. Both must be rated for the voltage you are measuring, or the meter itself becomes the hazard. One more battery warning: charging or discharging an unprotected battery too fast can overheat it and make it gas, on top of the short circuit danger you already know.

Lightning grounding is a system, and every part of it has a reason. A lightning arrester for a coax line mounts on a grounded panel right where the feed lines enter the building, so the surge meets ground before it meets your house. Every ground rod outside, including the one on that panel, must be bonded together with heavy wire or strap, because separate unconnected grounds can sit at different voltages during a strike and arc between them. Ground leads should run short and direct, with no sharp bends, since a surge does not like turning corners. The rules for what counts as a legal ground come from your local electrical codes.

Towers have their own grounding recipe: a separate eight-foot ground rod for each tower leg, bonded to the tower and to each other. Guy wires get a small detail that saves towers: a safety wire threaded through each turnbuckle so vibration cannot slowly unscrew it over the seasons. A crank-up tower is never climbed while it is up. It must be cranked fully down, or fitted with mechanical safety locks, before anyone leaves the ground. Measure your power line clearance the pessimistic way, for the day something falls: if the antenna comes down, no part of it may land within 10 feet of the power wires. And never hang an antenna on a utility pole. The pole carries high-voltage lines, and your antenna could contact them.

Radio waves are non-ionizing radiation. Unlike radioactivity, an RF signal does not carry enough energy to change your cells or damage DNA, which is why the FCC regulates it as an exposure and heating question instead of a poisoning one. The limits change with frequency because your body absorbs RF energy more strongly at some frequencies than at others; the strictest limit of all, the lowest maximum permissible exposure, is at 50 MHz. What decides the exposure near an antenna is a handful of things working together: the frequency, the power, the antenna gain, how far away people are, and the duty cycle. Duty cycle is simply the percentage of time your transmitter is actually on the air during the averaging period. Exposure limits are about the average, so a station transmitting half the time averages half the exposure: drop the duty cycle from 100 percent to 50 percent and the allowable power density doubles. You can show your station complies by calculation, by computer modeling, or by measuring with calibrated equipment, and you must run that evaluation again every time you change anything in the transmitter or antenna system. The responsibility sits with one person: the station licensee. Practical ways to lower exposure are simple. Move the antenna farther from where people live and sit, and never touch an antenna while it is transmitting, because that is exactly how RF burns happen.

Key facts:

• If it can fall on a power line, do not put it there. No exceptions
• Capacitors stay dangerous after power off. Discharge and verify before touching
• Never climb a tower alone, in bad weather, or without proper safety gear
• Keep people clear of antennas while transmitting, and ground everything where cables enter the house
• Black wire is hot, white is neutral, green or bare is ground; fuses go in the hot wire only
• Duty cycle is the percent of time you are actually transmitting, and exposure limits use the average
• Every ground rod gets bonded to all the others with heavy wire or strap
• A crank-up tower is climbed only when fully retracted or mechanically locked

Start T0 on the learning path