Modes: what varies, how wide, what the name says

This section asks which mode suits a job, how much spectrum it occupies, and what a run of capital letters stands for. Two habits answer most of it: ask what the carrier is doing, and read the name literally.

What varies, how wide, who else hears you

Begin with the property of the carrier that carries the message. Change its size and you are in the amplitude family, whose full version is a carrier flanked by a matching pair of sidebands and whose economical version keeps one and throws the rest away. Change its timing, the frequency or the phase, and you have the family used for channelised local work and for keyed data pushed through a voice transceiver. Change nothing but on and off, and the keyed carrier spells the message itself. Both ends must agree which sideband: the lower one on the lowest bands, the upper one on 20 metres and every higher frequency.

Width decides more than tidiness. A narrow receiver passband lets in less noise, so narrow modes stay readable where a wide one has already sunk from sight, which is why weak-signal work on VHF and UHF avoids it. The wide constant-amplitude mode pays that back locally: it ignores amplitude noise and locks onto the strongest signal on the channel, suppressing the rest, so the audio is clean and the dial is forgiving. The rest of the section is vocabulary with a method: expand the abbreviation, then check every word of it against what the thing does.

• Locating a transmitter is a bearing problem: bearings taken from several places and crossed give the position of a jammer or a hidden station.
• One activity counts contacts against the clock, so its exchanges carry only what identification and the log require; a station names its place with a short letter-and-number designator for a map rectangle.
• One packet network carries whatever short data is offered — position, weather, a few words of text — and plots the senders live on a shared map.
• A digital mode sends coded symbols rather than a continuously varying waveform; the weak-signal ones use timed fixed-length transmissions and heavy coding to decode below the noise.
• A mesh is not a voice mode: it is a data network of commercial Wi-Fi hardware with its firmware replaced.

Where the answers are lost

• Trading the real difference for an imagined one. The narrow mode's advantage is width and it pays for that at the dial; distractors credit it instead with easy tuning, immunity to interference or indifference to a high SWR, and in the other direction saddle the wide mode with poor audio or hard tuning, when its one real cost is that only the strongest signal on the channel is heard.
• Guessing bandwidth from familiarity. Distractors squeeze speech into 1 kHz, stretch keying to 2.4 or 15 kHz, inflate an FM channel to 150 kHz, halve or double a television channel, or rank a voice or picture mode narrower than keying.
• Reading the combined choice as generosity or as a trick. It is right exactly when every item stands on its own: a packet frame does carry addressing, a check value and a request to send it again, while what a spacecraft measures about itself is its own condition, a tracking program is fed the orbit, not the transmitter power or a past Doppler reading, and a hunt needs a bearing, not meters on your own feed line.
• Mixing up the satellite effects. A frequency drifting through a pass is relative motion; a strength swinging in a steady rhythm is the spacecraft turning; and too much uplink power takes the transponder from everyone else rather than overloading batteries, rebooting a computer or commanding a mode; the fair-share check is your downlink against the beacon.
• Sorting linked systems by name rather than by function. Over-the-air control of a node is keypad digits, not a squelch tone or an internet password; access from an application is granted only against proof of licence, since the user's own transmitter is not involved; and a station joining two networks is named for the joining.
• Translating an abbreviation by ear. Distractors offer ultraviolet for a band letter, a low-energy or low-elevation orbit, keying by pulse or power instead of by phase, compression or encryption for a repeat request or for an analogue picture standard, and a form of propagation for what is only keyed Morse.

Try it yourself