E2: Operating Procedures

Yes, you can hold a small radio in your backyard, point an antenna at the sky, and have a conversation through a satellite the size of a microwave oven flying overhead at 17,000 miles per hour. This group covers how those satellites move, how they relay your signal, and the equipment quirks that come with working them.

How a satellite moves: passes and orbits

An amateur satellite does not hover; it circles the Earth, so from your spot on the ground it rises on one horizon, arcs across the sky, and sets on the other. Each time it comes over is called a pass. Many amateur satellites travel in a roughly north-south polar orbit, looping over the poles while the Earth turns underneath. The part of a pass where the satellite is heading upward in latitude, climbing from the southern sky toward the north, is the ascending pass, and its direction is from south to north. (When it is coming back down toward the south, that is the descending pass.)

To know when and where a satellite will appear, your tracking software needs the math that describes its orbit. That set of numbers is called the Keplerian elements (named after Johannes Kepler, who worked out the laws of orbits). In plain words, Keplerian elements are the parameters that define the orbit of a satellite, things like how tilted the orbit is and how high it goes. Feed them into a tracking program and it predicts every pass.

One special orbit deserves its own name. A satellite parked very high above the equator, circling at exactly the speed the Earth rotates, appears to hang motionless in the sky. That kind, which appears to stay in one position in the sky, is called geostationary. ("Geo" = Earth, "stationary" = not moving; from the ground it just sits there.) You can aim a fixed dish at it and never move it.

What "mode" means for a satellite

This is a confusing bit of jargon, so go slow. When hams say the "mode" of a satellite, they do not mean SSB versus FM. For a satellite, the mode is the satellite's uplink and downlink frequency bands. The uplink is the frequency you transmit up to the satellite; the downlink is the frequency it sends back down to you. So a satellite's mode just tells you which band to talk on and which band to listen on.

These bands are written with letter codes. The letters in a satellite's mode designator specify the uplink and downlink frequency ranges. Two letters you must know: "L band" and "S band" specify the 23-centimeter and 13-centimeter bands respectively. (L band = 23 cm, around 1.2 GHz; S band = 13 cm, around 2.4 GHz. A memory hook: L comes before S, and 23 is a bigger wavelength number than 13.)

The transponder: the satellite's relay box

Most conversational satellites carry a transponder, a relay that hears a whole slice of band on the uplink and rebroadcasts that entire slice on the downlink at the same time. A linear transponder relays a chunk of spectrum faithfully, so it can carry any signal in that slice at once, SSB, CW, and more, all these choices, for many users simultaneously. (This is unlike a simple FM repeater, which handles only one conversation at a time.)

Some are inverting linear transponders, and the test loves their three telltale traits, which is why the answer is "all these choices are correct":

• The signal position in the band is reversed, what was at the low end of the uplink slice comes out near the high end of the downlink slice.
• Upper sideband on the uplink becomes lower sideband on the downlink, and the other way around. (Upper and lower sideband, USB/LSB, are the two flavors of single-sideband voice.)
• Doppler shift is reduced because the uplink and downlink shifts are in opposite directions. ("Doppler shift" is the small frequency change caused by the satellite racing toward you and then away from you, the same effect that makes a passing siren change pitch. With an inverting transponder the two shifts partly cancel.)

How does it pull off that flip? The uplink signal is mixed with a local oscillator signal and the difference product is transmitted. In plain terms, the transponder blends your incoming signal with a steady internal tone (the "local oscillator") and sends out the difference between them. Subtracting in that way is exactly what reverses the band and flips the sidebands.

Be a polite, low-power user

A linear transponder shares its limited transmit power among everyone using it at that moment. So you should keep your effective radiated power (ERP) limited, that is, do not blast it. (ERP is just a measure of how strong your signal actually is by the time it leaves your antenna.) The reason: if you shout, the transponder pours more of its power into relaying you and less into everyone else. You must limit ERP to avoid reducing the downlink power to all other users. Use only as much power as you need to be heard.

Antennas: beating spin and twist

Satellites tumble, and their signals also get twisted as they pass through the upper atmosphere. Two problems result: spin modulation (the signal fading in and out as the satellite rotates) and Faraday rotation (the wave's orientation slowly rotating as it crosses the charged layers of the atmosphere). The cure for both is a circularly polarized antenna. Instead of holding its waves flat (horizontal or vertical), this antenna corkscrews them in a spiral, so no matter how the satellite's signal is twisted when it arrives, the antenna still catches it.

Store-and-forward satellites

Not every satellite is a live relay. Some are flying mailboxes. The purpose of digital store-and-forward functions on a satellite is to hold digital messages in the satellite for later download. You upload a message when the satellite is over you; it stores it, carries it around the world, and someone elsewhere downloads it on a later pass. The satellite is the courier.

Hams have sent pictures over the air for decades. There are two big families: fast-scan television (FSTV), which is full-motion video like the old broadcast channels, and slow-scan television (SSTV), which sends a single still image slowly, encoded as audio tones. This group covers both.

Fast-scan (NTSC) analog television

NTSC is the name of the old North American analog TV standard (it stands for the committee that wrote it). A complete picture in that system is called a frame, and an NTSC frame is built from 525 horizontal lines stacked from top to bottom. Memorize that number: 525.

Those lines are not drawn straight down in order. The system uses interlaced scanning to reduce flicker, generated by scanning the odd-numbered lines in one field and the even-numbered lines in the next. (A "field" is half a frame. The screen paints lines 1, 3, 5... then comes back and fills in 2, 4, 6..., and the two half-pictures interlace like fingers.)

To save bandwidth, analog fast-scan TV uses vestigial sideband modulation. First the definition: vestigial sideband modulation is amplitude modulation in which one complete sideband and a portion (a vestige) of the other are transmitted. (Amplitude modulation normally sends two mirror-image sidebands; here we keep one whole and just a stub of the other.) The benefit for TV is that vestigial sideband reduces the bandwidth while increasing the fidelity of the low-frequency video components, you save spectrum without smearing the broad, slowly-changing parts of the picture.

There is a clever practical trick on the 70-centimeter band: you can use an ordinary, off-the-shelf cable-ready TV set to watch ham fast-scan video. The technique is transmitting on channels shared with cable TV, so the consumer TV, which already knows those cable channel frequencies, tunes the ham signal right in.

Digital television (DVB-T)

Modern digital ham TV often uses DVB-T (Digital Video Broadcasting, Terrestrial). Two ideas come up:

• Modulation types: amateur DVB-T signals use QAM and QPSK. (QAM is "quadrature amplitude modulation" and QPSK is "quadrature phase-shift keying", two digital schemes that pack data by varying a signal's amplitude and/or phase. You just need to recognize the names.)
• Coding rate: digital systems add extra correction data so the receiver can fix errors. A coding rate of 3/4 means 25% of the data sent is forward error correction data. (Think of the fraction as "useful data over total"; 3 useful out of 4 total leaves 1 in 4, or 25%, as the error-correction overhead. "Forward error correction" means extra bits sent ahead of time so mistakes can be repaired without asking for a resend.)

Slow-scan television (SSTV)

SSTV sends one still picture as a stream of audio tones, slowly, often over a regular SSB voice channel. Because it is just audio, the receiver you use to receive and decode SSTV with the Digital Radio Mondiale (DRM) protocol is an SSB receiver. (DRM here is a digital protocol for sending pictures; the point is that an ordinary single-sideband radio carries it.)

Several details about how SSTV encodes a picture:

• Brightness: in analog SSTV, the brightness of each spot in the picture is encoded by tone frequency, a higher or lower pitch means a brighter or darker pixel.
• Color: color information is sent by transmitting the color lines sequentially, the red, green, and blue parts of each line are sent one after another rather than all at once.
• Starting a new line: the receiving software knows to begin a new picture line when it hears specific tone frequencies that act as a sync signal.
• Identifying the mode: SSTV has many sub-modes (Scottie, Martin, Robot, and others). At the start of a transmission a vertical interval signaling (VIS) code is sent, and its function is to identify the SSTV mode being used so the receiver decodes the picture correctly.

This group is about competitive and long-distance operating: contests (organized events where you make as many contacts as possible in a set time), chasing DX (distant or rare stations), operating your station from afar, and how the community records and confirms all those contacts. "DX" is old telegraph shorthand for "distance," so a DX station is a far-away one, often in another country.

Working DX and pileups

When a rare station shows up, dozens or hundreds of operators call at once. That swarm is a pileup. Cutting through it is about discipline, not volume. To identify your station when contacting a DX station during a contest or in a pileup, send your full call sign once or twice, no more. Partial call signs and endless repeating just clog the frequency and slow everyone down.

You will also notice rare DX stations often listen on a different frequency than they transmit on. This is called working "split." DX stations transmit and receive on different frequencies for all of these reasons: it spreads the calling crowd across a range of frequencies so the DX can pick out individual stations, it keeps the DX station's transmit frequency clear so everyone can hear it, and it generally tames an unruly pileup. The takeaway answer is simply "all these choices are correct."

One handy role in the DX world is the DX QSL Manager. ("QSL" is shorthand for "I confirm.") The function of a DX QSL Manager is to handle the receiving and sending of confirmations for a DX station, a volunteer, often in another country, who manages all the paperwork of confirming contacts so the rare operator does not have to.

VHF/UHF contesting

On VHF and UHF, serious long-distance contest work happens in the weak-signal segment of each band, the low portion set aside for SSB and CW rather than FM. During a VHF/UHF contest you will find the highest level of SSB or CW activity in the weak-signal segment of the band, with most of the activity near the calling frequency. (A "calling frequency" is an agreed-upon spot where everyone goes to make initial contact before moving off to chat.)

One band is off-limits to contesting entirely: amateur radio contesting is generally excluded from the 30-meter band. (By gentleman's agreement, 30 meters is kept quiet for digital and CW work, no contests, no wide signals.)

Remote operation

You can run your station from across the room or across the country. Two facts:

• Identifying: when a US-licensed operator runs a station by remote control and the remote transmitter is also located in the US, no additional indicator is required. You just use your normal call sign as if you were sitting there.
• Latency: running a station remotely introduces a small lag. The word for the delay between a control operator action and the corresponding change in the transmitted signal is latency. (If you press the key and the signal goes out a beat later, that gap is latency.)

Logging and confirming contacts

Hams keep logs of their contacts and trade them electronically, so standard file formats matter:

• ADIF is the format used for exchanging amateur radio log data between programs. (It stands for Amateur Data Interchange Format.)
• Cabrillo is a standard for the submission of electronic contest logs, the format contest sponsors want when you send in your score.
• Logbook of The World (LoTW) is the ARRL's online confirmation system, and it can confirm all of these choices, contacts across many modes and bands, by matching both operators' uploaded logs.

Memory hook: ADIF is for swapping a log between programs; Cabrillo is for submitting a log to a contest.

Mesh networks

Hams also build high-speed data networks over radio, called mesh networks (every node relays for the others, like a net of interconnected links). These typically use repurposed consumer Wi-Fi gear: the equipment commonly used is a wireless router running custom firmware. ("Firmware" is the built-in software inside the router; hams replace it with special ham-radio firmware.) And the frequencies used for amateur mesh networks are those shared with various unlicensed wireless data services, the same general bands as Wi-Fi, where hams have overlapping privileges.

VHF and UHF signals normally die at the horizon. This group is about the clever tricks that reach further, bouncing off the Moon and off meteor trails, plus the digital modes and position-reporting system that make modern VHF/UHF operating tick.

Two ways to beat the horizon

• EME (Earth-Moon-Earth), also called "moonbounce": you aim a big antenna at the Moon and bounce your signal off it to anyone else who can see the Moon. The round trip is about half a million miles, so signals come back fantastically weak. A standard method for establishing EME contacts is time-synchronous transmissions alternating between stations, the two operators take strict turns on a shared clock (one transmits while the other receives, then they swap), which lets weak-signal software average and dig the signal out.
• Meteor scatter: tiny meteors constantly streak into the atmosphere, leaving brief trails of ionized (electrically charged) gas that can reflect VHF signals for a second or two. You fire short bursts hoping one bounces off a trail. The digital mode designed for meteor scatter communications is MSK144, built to cram a whole exchange into those fleeting reflections.

The WSJT-X weak-signal modes

Most modern EME and weak-signal VHF work uses modes from the WSJT-X software family. The two for this group:

• JT65: its defining trait is that it decodes signals with a very low signal-to-noise ratio, it pulls in stations far too weak to hear by ear. Its modulation is multitone AFSK (audio frequency-shift keying using many tones; the data is sent as a pattern of different audio pitches).
• Q65: the mode designed for EME communications. It is an updated relative of JT65, and the key difference is that with Q65 multiple receive cycles are averaged together, stacking several listening periods to recover a signal even weaker and more fluttery than JT65 can handle.

FT8/FT4 in VHF contests

The wildly popular FT8 and FT4 modes are covered fully in group E2E, but one VHF-contest detail lives here. In normal use these modes exchange a signal-to-noise report, but in a VHF contest, the grid square replaces the signal-to-noise ratio in the exchange. (A "grid square" is a short code like EN70 that identifies your location on a worldwide map; in VHF contests, distance between grid squares is what scores points, so that is what gets traded.)

APRS: live position reporting

APRS (Automatic Packet Reporting System) lets stations broadcast their position, weather, and short messages, often plotted live on a map. It is the go-to tool for tracking things that move. For example, the technology used for real-time tracking of balloons carrying amateur radio transmitters is APRS, a high-altitude balloon beeps out its GPS position and the whole world watches it drift across the map.

Several technical details about how APRS works under the hood:

• Protocol: APRS rides on the AX.25 digital protocol. (AX.25 is the standard packet-radio data protocol, the ham adaptation of an old wired networking standard.)
• Frame type: APRS beacon data is carried in an Unnumbered Information frame. (In AX.25, an "Unnumbered Information" frame is a one-shot packet that does not need an acknowledgment, perfect for a beacon that just shouts its position and moves on. A "frame" is one packet of data.)
• Relaying: APRS stations relay each other's data by packet digipeaters. (A "digipeater" is a digital repeater: it hears a packet and rebroadcasts it, extending the network's reach.)
• Path strings: APRS packets carry a path telling digipeaters how far to relay them. The path WIDE3-1 designates three digipeater hops requested with one remaining. The first number (3) is how many hops were originally asked for; the second number (1) is how many are still left, so this packet has already been relayed twice and has one hop to go.

The shortwave bands today are alive with digital signals, those warbling tones you hear that a computer turns into text and data. This group sorts out the big modern HF digital modes. The hardest part is keeping the similar names straight, so we will lean on memory hooks.

How HF data is keyed

Most data modes below 30 MHz use FSK (frequency-shift keying), meaning the data is sent by shifting the signal between different frequencies (tones). There are two ways to produce it, and the test asks the difference:

• Direct FSK shifts the radio itself: it modulates the transmitter VFO (the variable-frequency oscillator that sets the radio's frequency).
• Audio FSK (AFSK) instead feeds shifting audio tones into a regular SSB transmitter. So the headline difference: direct FSK modulates the transmitter VFO, while audio FSK just sends tones in through the microphone input.

The FT/FST family (and timing)

These are the dominant weak-signal modes, and they are structured, not free-form chat. They depend on accurate clocks:

• What synchronizes the timing: WSJT-X modes coordinate transmit and receive by synchronization of computer clocks. Both stations' computers must agree on the time to the second, so each knows exactly when a transmission starts. (People sync their PC clocks to internet time servers for this.)
• FT8 uses a 15-second transmission cycle, every exchange happens in tidy 15-second slots. Among the modes in this group, FT8 also has the narrowest bandwidth.
• FT4 is the faster cousin built for contesting. The "4" in FT4 refers to four-tone continuous-phase frequency-shift keying, it shifts among four tones, smoothly, without abrupt phase jumps.
• FST4 is a slow, ultra-weak-signal mode for the low bands, and its description is "all these choices are correct" (it offers a range of selectable transmission lengths and is optimized for the noisy low-frequency bands).

Memory hook: FT8 = the everyday 15-second mode; FT4 = faster, 4 tones, for contests; FST4 = the patient low-band weak-signal specialist.

The JT/Q weak-signal pair on HF

You met JT65 and Q65 in group E2D for EME; the same distinction applies on HF. The key contrast worth re-stating: Q65 differs from JT65 in that multiple receive cycles are averaged. Averaging several listening periods is what lets Q65 reach even deeper into the noise.

WSPR: the propagation beacon mode

WSPR (pronounced "whisper," for Weak Signal Propagation Reporter) is not for conversation at all, it is for testing where your signal can reach. You send a tiny beacon and automated receivers worldwide report hearing you. Because it is one-way and automated, WSPR is the mode that does NOT support keyboard-to-keyboard operation (you cannot type back and forth on it like a chat).

PSK31: live keyboard chat

PSK31 is the classic real-time "type and read" mode, like an over-the-air instant messenger. Its clever feature is variable-length character coding, common letters get short codes and rare letters get longer ones (similar in spirit to Morse code), which keeps it efficient in a very narrow signal. (The "31" is its data speed in bits per second.)

PACTOR and ALE: moving files and finding each other

• PACTOR is a robust mode built for reliable data transfer, it can transfer binary files (any computer file, not just text), which is why it is used for HF email and bulletins. Among these modes, PACTOR IV has the highest data throughput under clear conditions, the fastest of the bunch when the band is good. (Each PACTOR generation, I through IV, is faster than the last.)
• ALE (Automatic Link Establishment) is a system for stations to automatically find a working frequency and connect. ALE stations establish contact by constantly scanning a list of frequencies and activating the radio when the designated call sign is received. The radio quietly listens across many channels until it hears its own call, then springs to life. (No human has to be sitting there guessing which band is open.)

Quick comparison to lock it in

Mode	What it is best at
FT8	Quick weak-signal contacts, 15-second cycles, narrowest bandwidth
FT4	Faster contest version, four-tone keying
WSPR	One-way propagation beacon (no keyboard chat)
PSK31	Live keyboard-to-keyboard conversation, variable-length coding
PACTOR (IV)	Reliable file transfer, highest throughput
ALE	Automatically finding and linking on a clear frequency