A
- AM (amplitude modulation)
- Carrying a message in the changing height of a wave. → ch. 5 · Carrying a voice: AM
- amplitude
- How tall a wave swings from its resting line; the first of the three knobs. → ch. 1 · What is a wave?
- antenna
- A wire shaken to throw a wave, and shaken by waves that wash over it: the doorway between circuits and open space. → ch. 8 · Throwing and catching waves
B
- backoff
- The secret die a polite radio rolls after the air goes quiet, so eager talkers don’t all pounce at once. → ch. 23 · Taking turns
- bandwidth
- The width of the shelf of frequencies a signal’s recipe occupies. → ch. 16 · The wave recipe
- beamforming
- Timing a row of small antennas so their ripples pile up in one chosen direction: a beam with no moving parts. → ch. 25 · Aiming the invisible
- beat
- The slow wave that appears when two waves are multiplied together, throbbing at the gap between their two speeds; a receiver’s mixer lives on it. → When waves multiply
- bit
- One yes-or-no; the atom every digital message is built from. → ch. 17 · Turning waves into numbers
C
- capture effect
- When two FM signals share a frequency, the stronger one wins outright and the weaker vanishes, so FM comes through either crystal-clear or not at all. → ch. 6 · A steadier ride: FM
- carrier
- The steady high-frequency wave that a message is pressed onto for the journey. → ch. 5 · Carrying a voice: AM
- cell
- One small patch of the phone network’s quilt, tended by its own quiet tower. → ch. 26 · A quilt of cells
- complex number
- The spinning arrow written as one number, so a wave’s amplitude and phase can travel through the math together. → The spinning arrow
- compression
- Squeezing the predictable and the unhearable out of the bits before they travel. → ch. 17 · Turning waves into numbers
- constellation
- The map of every amplitude-and-phase symbol a scheme uses, drawn as stars. → ch. 20 · Constellations & 64-QAM
D
- decibel (dB, dBm)
- Counting a signal’s strength in tenfolds, so multiplying becomes adding; dBm anchors the count to one milliwatt. → Thinking in decibels
- Deep Space Network
- The three giant ear-complexes, spaced a third of the world apart so one always faces the sky, that catch spacecraft whispers from beyond the planets. → Talking to the edge of the solar system
- detector
- The receiver part that reads the message back off the wave: height for AM, speed for FM, timing for phase. → ch. 14 · Inside the receiver
- dipole
- The plainest real antenna: two rods fed in the middle, about half a wavelength end to end. → A field guide to antennas
- duplex
- Talking and listening at the same moment by using two frequency lanes at once. → ch. 23 · Taking turns
E
- encryption
- Scrambling bits with a secret key so anyone can record the wave and still hold nothing but coin flips. → ch. 27 · Anyone can listen
- error correction
- Guardian bits woven among the message bits so the far end can find and flip damaged ones back. → ch. 19 · Keeping bits honest
F
- Faraday cage
- A box of metal that waves can neither enter nor leave: an elevator, a microwave door, a foil room. → ch. 11 · What stops a wave
- FM (frequency modulation)
- Carrying a message in the changing speed of a wave’s wiggle, which shrugs off crackle. → ch. 6 · A steadier ride: FM
- Fourier transform
- The un-adding machine: probe a wave with every pure tone in turn, multiply and average, and the readings are the wave’s recipe. Its fast version, the FFT, hums inside every modern radio. → The un-adding machine
- frequency
- How many times a wave wiggles each second, measured in hertz; the second knob. → ch. 1 · What is a wave?
- frequency hopping
- Skipping between lanes many times a second on a pattern only your partner knows. → ch. 24 · Hiding in the noise
G
- geostationary
- The magic altitude where one orbit takes one day, so a satellite hangs over a single spot forever. → Towers in the sky
- GPS
- Satellites whispering the time from atomic clocks, so your phone can turn tiny delays into a place on the map. → ch. 28 · Echoes that measure
- groundwave
- A low-frequency wave that hugs the curve of the earth for a few hundred miles. → ch. 12 · Bouncing off the sky
H
- handoff
- The mid-sentence leap of your call from one cell tower to the next, arranged so you never hear it. → ch. 26 · A quilt of cells
- harmonic
- A whole-number multiple of a pitch; stacked harmonics are the ingredients of every repeating wave. → ch. 16 · The wave recipe
- hertz (Hz)
- One wiggle per second, named for the man who first made radio waves on purpose. → ch. 3 · From ripples to radio
I
- interference
- What happens when waves share a spot: their heights simply add, heaping up or canceling out. → ch. 4 · When waves meet
- inverse-square law
- Twice as far means a quarter as strong: the tax every spreading wave pays with distance. → ch. 9 · Fading away
- ionosphere
- The mirror in the sky: a high electrified layer that bounces some waves back down, especially at night. → ch. 12 · Bouncing off the sky
K
- key exchange
- The public mathematical dance that leaves two radios holding the same secret while eavesdroppers hold nothing. → ch. 27 · Anyone can listen
M
- Manchester coding
- Writing every bit as a step in the middle of its beat, so the signal carries its own clock. → ch. 19 · Keeping bits honest
- microphone
- A thin drumhead that turns the push of sound into a wiggling electrical wave; a speaker is the same trick run backward. → ch. 15 · From your voice to a wiggle
- MIMO
- Multiple antennas at each end running more than one stream of data at once, so the tangle of echoes that muddies a single signal instead keeps the streams apart. → ch. 25 · Aiming the invisible
- mixer
- The receiver part that combines the station with a homemade wave, sliding it down to one easy workbench frequency. → ch. 14 · Inside the receiver
- modulation
- Wiggling a carrier’s knobs on purpose so a wave carries a message. → ch. 5 · Carrying a voice: AM
- multipath
- Copies of a signal arriving by different bounced routes, painting dead spots and smearing fast symbols. → ch. 4 · When waves meet
N
- near field
- The part of an antenna’s field that never flies off as a wave but swells and fades right at its surface, close enough that a tap-to-pay card works only on contact. → Everyday radio mysteries
- noise floor
- The ever-present grass of hiss (warm electronics, lightning, the sun, the Big Bang’s afterglow) every signal must stand above. → ch. 10 · Where the hiss comes from
- Nyquist rule
- Snapshot a wave more than twice as often as its fastest wiggle, or a false wave sneaks into your numbers. → ch. 17 · Turning waves into numbers
O
- OFDM
- Sending hundreds of slow symbol streams side by side on thin subcarriers: the orchestra no echo can trip. → ch. 21 · An orchestra of carriers
- oscillator
- A self-pushing electrical swing that sings one pure note forever: the metronome of every radio. → ch. 14 · Inside the receiver
P
- phase
- Where in its cycle a wave is right now: a nudge earlier or later; the third knob. → ch. 1 · What is a wave?
- phase-shift keying (PSK)
- Sending bits as deliberate jumps in a wave’s timing, invisible to the ear but unmistakable to a machine. → ch. 7 · The third knob: phase
- phased array
- A team of small antennas fed split seconds apart, steering a beam electronically. → ch. 25 · Aiming the invisible
- photon
- The tiny packet a wave’s energy arrives in; faster wiggles make stronger packets, and only packets far beyond light’s can break molecules. → ch. 13 · Is any of this dangerous?
- polarization
- The direction a wave wiggles, remembered from the way its antenna was shaken; receivers catch best when they match it. → ch. 8 · Throwing and catching waves
- preamble
- The little hello of known wiggles at the front of a packet, played so the receiver can find the rhythm before the real bits arrive. → ch. 29 · The whole journey
Q
- QAM
- Mixing amplitude and phase into a grid of symbols so each slice of wave carries many bits. → ch. 20 · Constellations & 64-QAM
R
- radar
- Timing your own echo to measure distance, and its pitch-shift to measure speed. → ch. 28 · Echoes that measure
- repeater
- A relay that catches a whisper and re-shouts it, so two radios can talk across a mountain or a city. → ch. 26 · A quilt of cells
- resonance
- A swing answering only pushes timed to its own rhythm; tuning is choosing which pushes may pile up. → ch. 14 · Inside the receiver
S
- sampling
- Taking quick regular snapshots of a wave, the first step of turning it into numbers. → ch. 17 · Turning waves into numbers
- Shannon limit
- The hard ceiling on any channel’s speed: lane width times headroom above the hiss, and no cleverness beyond it. → ch. 22 · The speed limit
- sideband
- The pair of new waves that flank a carrier once a message is multiplied onto it; the message actually rides in them, just above and below the carrier’s own speed. → ch. 5 · Carrying a voice: AM
- sine wave
- The roundest wave there is: the shadow of a dot going around a circle, and radio’s favorite shape. → ch. 2 · Meet the sine wave
- software-defined radio (SDR)
- A radio that catches raw snapshots of the air and does everything after the antenna in math. → Hear it for yourself
- spectrum
- The whole run of frequencies, from AM’s rumble past light itself, divided into lanes. → ch. 3 · From ripples to radio
- spread spectrum
- Smearing a signal so thin across frequencies that it can hide below the hiss and dodge trouble. → ch. 24 · Hiding in the noise
- symbol
- One deliberate setting of the wave’s knobs, held for a beat; each symbol carries one or more bits. → ch. 18 · Bits on the air
T
- transceiver
- A transmitter and receiver sharing one set of machinery, like the radio in your phone. → ch. 14 · Inside the receiver
W
- wavelength
- The distance from one crest to the next; the faster the wiggle, the shorter the wave. → ch. 3 · From ripples to radio