📻 Why ShackLink?

Everything you need to control your ham radio remotely over your local network, or anywhere on the internet.

📡 End-to-End Data Flow

Antenna to rendered pixel in eight stages. The transmit half of the same picture is in the TX Subsystem section below.

Click the diagram for the full plate: both pipelines stage by stage, and the guarantee that holds at each hand-off. LAN clients (desktop, and mobile once it has discovered a server) take the multi-port path — 8080 control, 8081 audio, 8082 voice, 8085 spectrum — while browser, Home Assistant and remote mobile clients ride a single unified WebSocket on port 8084.

📦 Components

The ShackLink ecosystem includes multiple client applications for different platforms.

☝️ Touch Mode

A full-screen layout for a rugged touchscreen tablet: big keys, gloves welcome, nothing hidden behind a right-click.

New 2026-10. The normal window has far too much on it for a 12-inch screen in a vehicle. Touch mode is a second, separate layout for the same running server, designed for a Panasonic Toughbook-class tablet on a field table or a vehicle mount. Tap the touch cell on the flight strip, pick Touch Mode in the Start menu, or press Ctrl+K and type “touch”. The big DESKTOP key brings the normal window back exactly as you left it. Everything touch mode does goes through the same controls the normal window uses, so the two can never disagree.

• Sized for gloves. Every key is at least 12 mm on the glass. Sizes come from the panel’s real physical size, not from the Windows scaling setting, so the keys are the same size on any tablet.
• A palm cannot press anything. A key only acts when your finger is the only thing touching the screen. A hand resting on the glass blocks the keys until it lifts, so brace on the bezel.
• No hover and no right-click. Every function is a visible key, and every refusal is written on the page in words.
• The status strip along the top shows the frequency, the S-meter, the TX lamp and LISTENING TO, which picks the receiver you hear and nothing else.
• RADIO: a large frequency where tapping a digit sets the tuning step (1 Hz to 1 MHz), big DOWN / UP keys that repeat while held, a keypad with MHz and kHz enter keys, and twelve soft keys for band, mode, filter, AGC, noise blanker, noise reduction, notch, memories, split, RIT, volume (with squelch and NR level) and the keypad. One switch turns the page into a large waterfall.
• SPECTRUM: the panadapter. Tap to tune; drag with one finger to pan once zoomed in. ZOOM IN / ZOOM OUT keys replace pinching, PANADAPTER picks which receiver to show, and FOLLOW TUNING keeps what you hear in view.
• DIGITAL: the full FT8 / FT4 QSO console (decode list, wide graph, ANSWER, ENABLE TX, Tx1–Tx6, and a LOG IT / EDIT / DON’T LOG card), and CW, RTTY, PSK31 and Olivia with an audio waterfall, the decoded text and each decoder’s own settings keys. A MODES key reaches all twelve decoders. In CW, six macro keys send your macros.
• TRANSMIT: the transmit mode, the power in the transmitter’s own unit (with percentage presets on the radio), the transmitter’s state, TX monitor, your macros with the text each one sends, CW speed, and STOP.
• PTT: hold to talk, exactly like the TX tab’s push-to-talk. A quick tap does nothing, and the key says ON AIR, TEST, NOT KEYED or ENDED, and why it will not key in a mode other than voice.
• MORE: every tile of the Start menu on paged, finger-sized keys. A tile that opens a window steps touch mode aside first.

While touch mode is up it pauses the normal window’s own displays to save battery. On a narrow screen the photo panel can also be switched off from its right-click menu. The desktop client has the same five pages, working over the network.

RADIO: the large frequency, DOWN / UP, and the twelve soft keys, each showing its current value

RADIO switched to its large waterfall, with ZOOM, UP / STEP / DOWN, VOLUME, PANADAPTER and FOLLOW TUNING

SPECTRUM: the panadapter, tap to tune, with zoom keys instead of pinching

DIGITAL in FT8: the decode list, the wide graph and the QSO console on glass

DIGITAL in CW: the audio waterfall, the decoded text, and six macro keys that send CW

TRANSMIT: mode, power, the transmitter’s state, macros, CW speed and STOP

MORE: every Start menu tile on paged, finger-sized keys, grouped by category

👥 Client Management

Monitor and manage all connected clients from the server.

Accessing the Clients List

1. Open the Clients tab, or the Clients tile on the Tools tab or in the Start menu
2. Every connected client is listed with its type, IP address, port, last activity and client ID
3. The list auto-refreshes to show real-time connection status
4. Select a client and click Disconnect Selected, or Disconnect All

The connected-clients list with each client’s type, address and activity

🎧 Audio Streaming

Setup

1. Connect radio audio output to your sound card’s line input
2. Pick that device as the Audio Input in the station drawer (an SDR slot can have its own input, set per slot in SDR Management)
3. With an input chosen, streaming to clients starts automatically every time the server starts

HiFi MP3 Stream (192 kbps stereo)

The server simultaneously exposes a broadcast-quality MP3 stream at http://server:8084/hifi.mp3, served from the same unified port that hosts the web client and the WebSocket endpoint. One shared LAME encoder feeds every connected listener, no extra CPU per client. The encoder spins up automatically when the first client connects and idles when nobody’s listening.

• Works in any browser / VLC / mpv: paste the URL and go. No client install needed.
• ICY “Now Playing” metadata: clients that send Icy-MetaData: 1 receive the current rig / frequency / mode as a Shoutcast-style title, updated on every state broadcast.
• Discovery-aware: the UDP broadcast on port 8081 advertises the server hostname, HiFi, SDR, WebSocket ports, and LAN auth requirement (ShackLink Server;name=<hostname>;hifi=8084;sdr=8085;ws=8084;auth=<required|none>) so non-default configurations still auto-detect, clients can display servers by name, and native clients know up-front whether they need to authenticate.
• When to prefer which stream: use 12 kHz PCM for low-latency work (CW, digital modes, hearing your own TX), HiFi for casual listening or voice reception where broadcast fidelity matters more than ~1 s buffer latency.

Volume Control

The Audio tab includes a system volume slider that controls the default audio output device level. The volume level and the audio monitor on/off state are persisted across sessions.

Demo Mode

Enable demo mode to generate synthetic Morse code audio for testing without a connected radio. Useful for development, demonstrations, and learning.

📡 SDR Panadapter

Real-time spectrum and waterfall display from an SDR receiver.

SDR tab: scope, navigator, and 2D waterfall

3D terrain waterfall: the 2D scope stays live above it

SDR Management: assign a source, audio input, and per-slot decode mode (the eight modes that can run per slot: CW, RTTY, PSK31, NAVTEX, APRS, Olivia, FT8, FT4) to each of 8 slots. The mode can also be set from the desktop, web and mobile clients, and every slot’s output is visible in the Slot Decoders console.

Panadapter Settings: RF mode or IF mode with sideband offsets and pan policy

Waterfall popout: independent 3D view for a second monitor

Phosphor spectrum persistence over the 3D terrain

The same view under a different palette

Monitor Channels: per-band channel banks with Name, PI, Level, Heard and Note columns, and the Find stations, Prune not heard and Fill grid buttons

Source Types

• ExtIO Plugin (DLL): Load any ExtIO-compatible plugin (Airspy, SDRplay, etc.). Put the plugin DLLs in %LocalAppData%\ShackLink\ExtIO; a slot whose plugin you moved there still finds it. Device selection for adapters with multiple units is done through the plugin’s native GUI: click “Show Native GUI” after opening to access the plugin’s device picker.
• RTL-SDR (via rtl_tcp): Drives dongles through rtl_tcp, a small open-source driver server; because librtlsdr/rtl_tcp are GPL they are not bundled. Download them once into %LocalAppData%\ShackLink\rtl_tcp, or let Device Setup fetch the RTL-SDR Blog files from their publisher for you. Each local dongle is its own source entry; a network entry connects to a remote rtl_tcp instance (e.g. a dongle on a Raspberry Pi at the antenna). Direct sampling (HF on V3/V4 dongles) and bias-T are applied for real. Since 2026-10 a slot checks it opened the dongle it was bound to (USB order can change between the check and the open), and a dongle another program has open is listed by serial as in use by another program instead of vanishing from the list.
• HackRF: In-process via libhackrf. RX + TX, half-duplex, 1 MHz – 6 GHz, up to 20 MHz bandwidth. WFM / NFM demodulation with polyphase FIR decimation for high sample rates.
• Hermes Lite 2: Ethernet SDR transceiver via HPSDR Protocol 1. Full-duplex RX + TX, 48–384 kHz sample rates, N2ADR LPF/HPF filter board auto-selection, SWR protection with auto-unkey, and temperature monitoring. Live frequency changes via C&C registers.
• Native Sound-Card I/Q: A regular sound card capturing baseband I/Q from an external IF tap or quadrature converter. Pick the input device, set the sample rate, off you go.
• Icom Native CI-V: Control an Icom CI-V radio (e.g. IC-705) directly, with no OmniRig required, and use its built-in spectrum scope as a first-class SDR slot. Works over USB serial or over the network (Wi-Fi) via Icom’s RS-BA1 protocol, which carries control, scope, RX audio, and TX voice. The scope reassembles from the radio’s CI-V waveform frames; center mode spans VFO ± span, fixed mode uses the configured edges.
• IQ File Playback Slot: Map a slot to a saved I/Q recording (a SigMF pair, a .sigmf archive, or a legacy .sliq file) that loops forever, replaying captured spectrum like a virtual SDR. The LO is fixed at the recording’s center; click-to-tune moves the demod listen point, and FFT size stays adjustable.
• Test Signal (synthetic): Sine + Gaussian noise generator for development and testing without hardware.
• Public web receivers: KiwiSDR / Web-888 and SpyServer stations (their I/Q, our demodulator), and (new 2026-09) OpenWebRX / OpenWebRX+ receivers, which demodulate on the receiver and send audio plus their band’s FFT — including the digital-voice modes DMR, D-STAR, YSF, NXDN, P25, M17 and TETRA with who-is-talking metadata. The receiver’s profile is the slot’s span; ShackLink never switches it under the receiver’s other listeners.
• SoapySDR (new 2026-08): Airspy, Airspy HF+, LimeSDR, ADALM-Pluto, bladeRF, netSDR, and any radio on another machine through SoapyRemote — with the runtime installed separately (radioconda), receive only. Radios ShackLink already drives natively, and GPL-licensed modules, are kept out.
• USRP B210 and PlutoSDR-class boards (new 2026-09): through a separately installed companion program (UHD is GPL, so it never loads into ShackLink). Each board is a radio slot for its whole span plus up to seven narrow sub-receivers inside it; a B210’s second receive channel is a radio slot of its own, and (new 2026-10) so is a Pluto’s second input, RX2A, on boards that report one, with every input named as the board names it; a USRP radio slot is a no-hop wide-scan source; both can transmit through the normal interlocks. Still being commissioned on hardware.

Converters, transverters and LNBs (new 2026-09-15): any slot with a fixed-LO converter in front of it — a Ham It Up, a SpyVerter, a 2 m / 70 cm / microwave transverter, a Ku- or C-band LNB — is configured once with its offset (presets included) and from then on everything reads real RF, up to 300 GHz. An inverting LNB’s mirrored spectrum is put right at the source, a documented passband refuses tunes outside it, and transmit through a converter needs a declared drive cap.

Sources are assigned to slots from the SDR Management dialog (there is no longer a single source dropdown). Most drivers run in-process; only ExtIO plugins go through the 32-bit broker subprocess; RTL-SDR runs through the separate, user-supplied rtl_tcp process instead. Since 2026-10 a radio another slot is already using stays in the list, marked with the slot that holds it; picking it asks whether to move it, and moves it only if you say yes.

Web receiver browser: the KiwiSDR, Web-888 and Airspy directories in one sortable list over a zoomable world map, with a live spectrum, waterfall and audio preview before you give a slot to a receiver

FFT Size

The FFT combo on the SDR tab controls frequency resolution (4096 / 8192 / 16384 / 32768). Larger FFT = sharper waterfall when zoomed, at the cost of more CPU. Default is 16384. Changes take effect immediately and persist per-device.

Display Features

• Embedded + Popout: Scope + waterfall on the SDR tab, plus a “Popout Spectrum” button for a resizable window
• Auto-center: The waterfall automatically follows rig frequency changes for all SDR sources (HackRF, Hermes Lite 2, Sound Card I/Q, ExtIO/Broker), keeping the current signal centered on the display
• Click-to-tune: Click on the waterfall to set the rig frequency (or the SDR LO in RF mode)
• Drag-to-pan: Drag the spectrum or the frequency strip to slide the band; in IF mode the policy follows the server’s Pan mode setting
• Memory markers: Toggle “Show memory markers” to overlay stored memory frequencies on the spectrum
• DX spot markers, Live DX cluster spots drawn on the waterfall with callsign labels, color-coded by age
• Broadcast station markers: Known broadcast station frequencies overlaid on the waterfall with station name labels
• Gain / Contrast / dB floor: Adjustable via sliders on the popout toolbar
• Per-client zoom, Each connected client requests its own zoom span; a navigator overview channel shows where you are in the full band
• Navigator overview: A miniature full-band view showing the current zoom window position, enabling quick orientation within the band
• Phosphor spectrum: Persistence-overlay mode that accumulates spectrum traces over time, visualizing signal density and intermittent signals
• Phosphor histogram (experimental): An optional GQRX-style density/histogram color mode for the phosphor overlay (coarse cells + IIR smoothing), alongside the existing amplitude-hue and Gaussian-spread modes. Still an A/B experiment pending a verdict
• Waterfall view — three modes, not two: flat 2D, a full-pane 3D perspective terrain of spectrum history, and Split, which puts the terrain on the top half and the flat scroll underneath, joined on one shared instant: both show now at the seam, and history runs away from it in both directions. Right-click → Waterfall View, or the corner button, remembered per slot. Parallel projection is now the default for the full-pane view too, with the orbit camera one click away — under perspective only the centre column runs straight up, so edge ridges lean opposite ways, which reads as depth on its own and as a fault line the moment a flat waterfall sits underneath. GPU-accelerated via OpenGL with a CPU fallback that says so on a badge; heights and colours reuse the 2D waterfall palette for exact parity. All three modes ship on five surfaces — the SDR pane, the Lab spectrogram, the audio visualisation, mobile, and the web client
• Palettes: thirteen named waterfall gradients (two of them light) and twelve spectrum ones, one name-keyed set each, identical across the server, the desktop client, the Lab, Multiband, mobile and the browser. Both are picked from a grid of little rendered waterfalls rather than a list of names, and every tile renders the same synthetic frame so the tiles differ only in the palette. The spectrum set opens with a Solid (single colour) sentinel — the single-hue trace the SDR has always drawn
• Waterfall Ref (max-level): A Ref slider sets the top of the waterfall color scale (default 0 dBFS) so strong signals actually reach the top of the palette; gain headroom now runs to +60. Mirrored on the Lab spectrogram
• Zoom FFT: Server-side NCO + decimation zoom providing high-resolution narrow-band views without increasing overall FFT size
• AGC speed / IF gain / Filter presets: SDR receiver controls for AGC attack/decay speed, IF gain adjustment, and predefined filter bandwidth presets
• Multi-SDR slots, Up to 8 devices simultaneously, each in its own slot with independent LO, FFT size, demod settings, and optional per-slot decoder. Slot selector appears in all clients when multiple devices are active. One slot at a time feeds the audio output.
• Multiple identical devices: Run several of the same kind at once (multiple HackRF, SDRplay, Hermes Lite 2, or RTL-SDR units), each bound to its own slot by serial number (MAC address for Hermes Lite 2) so it keeps pointing at the same physical unit across USB re-ordering.
• SDRplay two-stage gain: RSP devices expose both gain stages on the panel: the IF Gain combo (0–59 dB) plus an RF LNA state combo (0 = max front-end gain; dB per state is band/model dependent: the SDR log’s “Gain report” line shows the real figures). Max sensitivity = IF 59 dB + LNA 0. Hardware AGC runs a 50 Hz loop at a −30 dBFS setpoint; switching AGC off returns to the last manual gain, and picking a manual gain switches AGC off. All of it persists per device and restores at slot start.
• Automatic recovery: A slot whose device dies or whose stream stalls restarts itself automatically (RTL, HackRF, Hermes Lite 2, SDRplay); the SDRplay API service self-heals if it stops or wedges; and streaming SDR slots restart automatically after the PC wakes from sleep.

Auto-Identify Signals (AI Recognition)

A neural-network classifier can scan the panadapter continuously and label every signal with its recognized mode. Right-click the spectrum display → Auto-Identify Signals to start a background scan of the selected slot; each confidently identified signal gets a small colour-coded chip centred on its carrier, with a guide line through the scope and waterfall.

• Colour-coded by family: CW, RTTY/FSK, PSK, MFSK, FT8/FT4, image (SSTV/WEFAX), packet/APRS, and voice each get a distinct chip colour
• Hover card: resting on a chip shows the top candidate modes with confidence, plus the measured frequency, bandwidth, SNR, and any decoder cross-check result
• Confident only: noise, unknown signals, and cross-check mismatches are hidden; a chip clears automatically the moment its signal goes off the air, and identified signals scrolled out of view are summarised by an edge arrow + count
• Show Signal Labels: a separate right-click toggle hides / shows the chips locally without stopping the scan
• Server-authoritative: the scan runs on the server and the chips are broadcast to the desktop client, which renders them identically. The classifier recognizes the modes in the installed model package; a signal outside that set is left unlabelled rather than guessed
• Scans you cannot see (new 2026-10): a scan left running on another slot is named in every slot’s right-click menu, with a Stop beside it, so it can no longer use CPU unnoticed

Auto-Identify needs raw I/Q, so it is available on IQ-capable sources (ExtIO/broker, RTL-SDR, HackRF, Hermes Lite 2, SDRplay, sound-card I/Q, and the synthetic test band); Icom scope slots and IQ-file playback are excluded, and it is refused while a slot is in IF-panadapter mode. A one-shot Identify Signal right-click option identifies a single signal (with optional decoder confirmation) even when the continuous scan is off.

RDS (Radio Data System)

RDS auto-activates whenever the SDR demodulator is in WFM: it is not a decode mode you select. It decodes the 57 kHz subcarrier for the station name (PS), programme identification (PI), RadioText, programme type, clock time, and traffic/network data.

It surfaces in the same idiom as the Auto-Identify chips above: a teal chip at the tuning marker on the SDR spectrum display reading “RDS <station name>”, dim until sync, with the full detail (PI, PTY, RadioText, clock, ECC / language, TMC / EON) on the hover card. The chip appears on the embedded SDR tab, on slot popouts, and in the SDR grid cells.

Station Slice and the SDR Grid

Two more ways to look at the receivers, both on the Tools tab and in the Start menu, and both on the desktop client too. Station Slice is an SDR view that stays zoomed on the station you are listening to — the passband plus a margin — and re-frames itself as the mode, filter or frequency changes, with its resolution written on its header. The SDR Grid is one window showing every running slot at once, each cell a full spectrum and waterfall with its own right-click menu, re-flowing as slots start and stop.

Station Slice: always zoomed on the station you hear

SDR Grid: every running slot in one window

Find Stations (Monitor Channels)

New 2026-10. Find stations works like a car radio’s autostore. Press it in the Monitor Channels window (the channel-count button on the SDR tab), or right-click a band on the SDR tab or a slot popout. It sweeps the band the receiver is on — even a band wider than the receiver can see at once — and stores every station it finds in a bank named after the band (FM BC, MW, and so on). Double-click a row to tune it.

• FM stations are named from their RDS. With the receiver in WFM and RDS on, each station found is visited briefly after the sweep and named from its RDS station name, and the receiver goes back to exactly where it was. If naming cannot run, it says why in words and the stations are stored unnamed. Two stations sending the same RDS identity are flagged as a possible image, never removed.
• A re-scan merges. New stations are added, the names you typed are kept, and a station not heard this time is marked, not deleted. Prune not heard is a separate, deliberate press.
• Fill grid is the old range fill (one channel every step, on the air or not), right for airband or repeaters; it now asks before it replaces a bank.
• It uses the Wideband Scan engine, so it will not start while a wideband scan is running, but the Wideband Scan window can stay open. Server only for now.
• Status: the first run on the air missed the weakest FM stations. The log now lists every signal the scan heard but left out, with its level, so the next runs can tell “never heard” from “heard and dropped”. RDS naming has not yet met a real radio.

Monitor Channels after Find stations on the FM broadcast band: each station it found, with its RDS name and PI code where one was heard, its level and when it was last heard

TETRA Receiver

New 2026-10. TETRA is the digital trunked radio used by many public-safety and utility networks. Set an SDR slot’s demodulator to TETRA and ShackLink’s own receiver decodes the cell it hears. Any local slot that delivers at least 36 kHz of I/Q can do it (not an Icom scope slot); an OpenWebRX receiver decodes TETRA itself and its slot shows that receiver’s own lines.

• The cell: network and cell identity, colour code, carrier frequency, whether the cell is encrypted, and its neighbouring cells.
• The four timeslots: what each one carries right now — control channel, a call, or nothing — and who is talking to which group.
• A call log and a short-data log: one row per transmission, and each short data message with its text when it was sent in clear.
• Voice: the first clear call plays on the slot’s audio, so every client listening to that slot hears it. Click a timeslot to listen to only that one. Encrypted calls are reported as encrypted and never opened.
• The codec tables are yours to import. ShackLink contains nothing written by ETSI. To hear voice, import ETSI’s own speech-codec archive once: SDR Management, right-click a slot’s Source cell, TETRA voice codebooks…. Everything else works without it.

The TETRA panel (Tools tab, or the Start menu’s Decode category) shows one band per TETRA slot with a lock lamp, the cell line and the four timeslots, over the call and short-data logs. The desktop client shows the same panel and can pin a timeslot too. Status: it decodes a real off-air recording of a clear cell, voice included, and matches ETSI’s own decoder on it; it has not yet been run against a live cell in the app.

The TETRA panel: the cell, its four timeslots and the call in progress, over the call and short-data logs

Architecture

ExtIO-based SDR sources use a 32-bit broker subprocess (ShackLinkSdrHost.exe) that loads the plugin, captures IQ data into a shared memory-mapped ring buffer. The server (64-bit) reads the ring, runs a windowed complex FFT, and produces dB-scaled spectrum lines at 30 fps. HackRF, Hermes Lite 2, and Sound Card I/Q run in-process (no broker), feeding IQ samples directly into the same FFT pipeline. Lines fan out to: the embedded display, the popout window, TCP 8085 stream (desktop client), and WebSocket binary frames (web/mobile/HA clients).

IQ Recording (SigMF)

Record live SDR I/Q to SigMF (the open Signal Metadata Format): either a SigMF meta+data pair or a single .sigmf tar archive, for later analysis or replay. The archive writer transcodes between sample formats (ci16, ci32, cf64, cu16). Zoomed (NCO + decimated) recordings are captured correctly and in real time. The legacy .sliq writer has been retired, but old .sliq files still play back. A recording can be replayed one-shot, or mapped to a looping IQ File Playback Slot (see Source Types above).

Per-Slot Audio Input

Each SDR slot can carry its own audio input device (an “Audio In” column per slot row in the SDR Management dialog) instead of one global input, so switching between, say, a USB-rig slot and an SDR slot no longer grabs the wrong sound device. Leave it empty to inherit the global Audio-tab device; SDR slots default to the SDR demodulator. The setting follows the audio-active slot (the one you hear).

📊 Audio Visualization

Real-time audio visualization with multiple display modes and customizable themes.

Waterfall (2D) on the Audio tab

Waterfall (3D terrain)

Oscilloscope: time-domain waveform

Visualization popout: 2D waterfall in its own window

Visualization popout: 3D terrain waterfall on a second monitor

Opening the Visualization Window

The Audio tab shows the visualization, and the Visualization tile on the Tools tab opens it in its own window, which stays open while you work with other controls. Its settings live on the display’s right-click menu.

Visualization Modes

Tuning from the Waterfall

The audio waterfall is tunable everywhere it appears: the Audio tab, the photo panel, and the Visualization popout.

Hover the audio waterfall and a dim ghost cursor follows the pointer, reading out the frequency under it, and, for modes you can retune, a preview of the decoder’s passband centred on the cursor, so you can see how it would sit on the signal before you commit. Click to place the decoder there. The marker then shows where the decoder actually landed, so if the value was out of range you see the clamp rather than a marker that quietly disagrees.

Only PSK31, Olivia and NAVTEX have a centre frequency to move; in other modes the click just parks the marker. Note that this sets the decoder’s centre frequency inside the audio passband: it is not the SDR waterfall’s click-to-tune, and the radio does not move.

Decoder Passband

A translucent decoder passband rectangle shows the span the active decoder is listening across: Olivia’s exact bandwidth (16/500 = 500 Hz), PSK31’s symbol rate, RTTY’s live auto-detected mark/space rails, and the fixed tone rails for NAVTEX, APRS, SSTV, WEFAX and CW. It is the nominal occupied span: an alignment aid, not a measured bandwidth. Right-click → Decoder Passband toggles it.

FT8, WSPR and JS8 show no passband: those are decoded by WSJT-X / JS8Call, not by ShackLink, so there is nothing honest to draw.

Palettes

The waterfall and the spectrum use the same named palettes as the SDR display — Classic (blue), Classic (green), CoolWarm, Viridis, Plasma, Inferno, Grayscale, Neon (cyan), Signal (teal), Semaphore, Rainbow and the rest — picked from a grid of small rendered waterfalls on the right-click menu, so a palette of a given name looks the same on every surface.

Display Settings

• Sensitivity – Adjust input gain for optimal display levels
• Contrast – Control the dynamic range of the visualization
• Freq Range – Set the maximum displayed frequency
• Peak Color – Choose peak indicator color (theme-based options)
• Peak Height – Set peak indicator height (1-10 pixels)
• Reverse – Flip waterfall scroll direction (new data at bottom)

📧 Winlink Radio E-mail

A native Winlink client: the mailbox on the server, sessions over the internet or the radio, operated at the station.

Winlink is the amateur-radio e-mail system. ShackLink composes, sends, receives and keeps Winlink mail itself — folders, attachments, a size estimate against the gateway limit, replies and forwards — and reaches the network two ways:

• Over the internet to the Winlink CMS, with the secure login every path requires.
• Over the radio through the modem program you already run — VARA HF, VARA FM, ARDOP, or a packet engine’s AGWPE port (Direwolf, UZ7HO SoundModem). ShackLink sets the dial and mode, holds the transmit lock for the whole session, keys the rig when the modem asks, and releases everything at the end, with every interlock an ordinary key-up has.

• A gateway table with distance and bearing from your locator, hand-entered or fetched from Winlink with a Web Services key.
• Session kinds: Winlink mail, peer-to-peer (directly to another station) and Radio-Only. A message is only ever offered to a session of its own kind.
• Station services that travel as ordinary messages: catalog requests, position reports from your grid, account options and the whitelist.
• Winlink’s standard forms (ICS-213 and the rest), imported from a Winlink Express template pack into ShackLink’s own store and filled in an embedded browser; a received form is drawn with the sender’s values.
• An account is created only on purpose (new 2026-10): a first Connect with no password no longer turns into a new Winlink account. On a reinstalled station that would be the wrong answer, so creating one is its own button — Account… → Create account… — and asks once, naming the callsign, the transport and the gateway.
• Operated at the station (changed 2026-10): the desktop client, web client and mobile app no longer carry a mailbox. Winlink is used from the server’s own screen, and the account password never leaves it.

The Winlink mailbox window on the server: folders, the message list and a preview

🎨 Themes, finishes & styles

Twenty-three colour themes (three of them light), fifteen button finishes, and independent dial and knob style sets.

Nothing here is a skin over a fixed layout — the palette drives the whole window (readouts, meters, panels, buttons, and every dropdown menu), the button finish is a separate axis from colour, and the VFO dial and the tuning knob each carry their own style set. They combine freely, so the pictures below are one axis at a time.

Light themes (new 2026-09-14): ShackLink Light, Paper and Blueprint. Light or dark is decided by the palette, not by a separate mode switch, and a light theme was designed and contrast-checked as a whole rather than produced by swapping a dark one’s background. The instruments follow it — scopes, navigators, Lab panes, meters, decoder scopes and instrument windows go light, the VFO readout becomes a paper screen with dark ink, and each waterfall palette is drawn as its designed light twin — with one switch to keep the dark instrument look and another to keep only the waterfalls dark. Four light dial styles (Paper, Blueprint, E-Ink, Enamel) and four light knob styles (Ivory Bakelite, Frosted Acrylic, Flat Light, Anodised Silver) joined the sets, for twenty and twenty-three in all. The web client stays dark on purpose.

A picture behind the app (new 2026-09-03): Station Settings → Background Image… shows one picture across the window wherever the app paints its own background, at the strength you choose; each SDR spectrum carries its own picture setting, with the waterfall fading as the picture strengthens.

🛠 Tools & Dashboards

Additional server-side tools, launched from the Tools tab’s grid of tiles.

The Tools tab: launcher tiles in six captioned columns (Operate, SDR, Decode, Analysis, Transmit, Reference). Settings moved behind the flight strip’s gear, into the Station Settings window.

Start Menu

The flight strip’s gear opens a Start menu: a tile for every window and tool, grouped by activity, with search, pinned favourites, and a Settings category holding a tile for each Station Settings block. It is built from the same command list as Ctrl+K, so the two always agree. Touch mode’s MORE page shows these same tiles on finger-sized keys.

The Start menu behind the gear: every tool as a tile, grouped by activity, with search and pins

Device Setup

New 2026-10. Tools → Device Setup answers “is my radio ready, and what do I do next?” It has one card per supported device — RTL-SDR, HackRF, SDRplay, SoapySDR radios, USRP B2xx, PlutoSDR, Hermes Lite 2, web receivers, OmniRig, Icom, ExtIO and sound-card I/Q. A check looks at this PC (driver files, the USB drivers Windows has given each device, the SDRplay service, the slots already running) without opening any radio, and each card then says in plain English where that device stands, with the exact steps for its state.

• A button that does the step, where that is safe: fetch the RTL-SDR Blog driver files into your own %LocalAppData%\ShackLink\rtl_tcp folder (no administrator rights needed), start Zadig already set to show every device and pick WinUSB, or install Analog Devices’ PlutoSDR USB drivers.
• Nothing is fetched without asking. A consent dialog names the file, where it comes from, its publisher, its licence and where it will go, and every download is checked against a pinned size and fingerprint before it is used. These files come from their publishers, not from ShackLink.
• Where a click-through licence or a large installer is involved (the SDRplay API, UHD, radioconda, OmniRig, Icom’s USB driver), the card opens the right download page and lists the steps instead.

Device Setup: a card per device, what this PC has, and the next step in plain English

Custom Colors

Click Colors in the Station Settings window (the flight strip’s gear → Settings) to open a color customization dialog — 60 colours in eleven groups. Personalize the frequency display, meters, background, accent colors, and other UI elements. Changes are saved and restored between sessions. Beyond individual accents, several complete color themes re-tint the whole window in one click from the Colors dialog or the title-bar Theme menu.

Color Settings, previewed live (an earlier capture: the dialog now carries 60 colours in eleven groups)

Neon theme

Green theme

Plasma theme

Theme Submenu (Title Bar)

A Theme submenu is added to the window’s title-bar system menu on both the server and the desktop client, so you can pick a color theme straight from the system menu without opening the full Colors dialog.

Photo Panel (Right-Click Modes)

The panel beside the callsign strip is no longer a static photo. Right-click it to cycle its modes: Photo (the operator’s picture), Audio Visualization (live spectrum / waterfall / scope), Knob (a Freq-Knob rotary VFO dial), SDR Spectrum (a full spectrum-and-waterfall view of the slot you are listening to, with the SDR tab’s own right-click menu), Station Slice (the same view permanently zoomed onto the station you are listening to), Propagation (live solar data), Signal Alerts (the threshold monitor), Decoder (a display-only mirror of the current decoder’s output), and Greyline (a day/night terminator map). The two spectrum modes keep their own look — palette, zoom and levels set there no longer rewrite the SDR tab. New 2026-10: while the station’s speech transcript owns the decoder strip, Decoder mode shows the transcript with its translation indented under it; and on a narrow screen Hide photo panel on any of its menus switches the panel off (the Start menu’s Photo Panel tile brings it back). The selected mode is saved between sessions. The desktop client shares the panel and the Knob mode.

Audio Visualization mode

Knob mode: rotary VFO dial with monitor knobs

Propagation mode: live solar data

Decoder mode: mirror of the active decoder

Greyline mode: day/night terminator map (the Photo mode default is shown at the top of this page)

Tooltips Toggle

Toggle Show Tooltips in the Station Settings window (the flight strip’s gear) to enable or disable hover tooltips across all controls. Useful for learning the UI, then turning them off once familiar. Main form uses ApplyTooltips(); separate dialogs have their own ToolTip instances with dark-themed custom draw.

Broadcast Guide

A searchable station database covering shortwave broadcasts (EiBi + HFCC), local FM and AM stations (FCC, filtered by operator location), and NOAA weather channels. Quick-select band buttons span LW through 11 m plus FM and WX. Filter by frequency range, country, language, source, or station name. The On Now toggle shows only stations currently broadcasting based on UTC schedule. Track VFO auto-filters to the rig’s current frequency. Double-click any row to tune the radio (sets both frequency and mode). All filter settings persist between sessions. Available on both server and desktop client.

Broadcast Guide: shortwave / FM / AM / NOAA station database with band buttons, On Now filtering, and click-to-tune

Dashboards & Popouts

The Tools tab also launches a set of standalone operations dashboards, each in its own window for multi-monitor use:

• Propagation: live solar data from hamqsl.com (solar flux, A/K indices, band conditions).
• Greyline Map: day/night terminator showing where HF propagation peaks, with your logged contacts plotted as callsign chips and great-circle arcs to your QTH — on a flat map or, new 2026-10, a 3-D globe (see below).
• Band Activity: which band is open, to where and how strongly, from eight activity sources, with a coverage record so a band nobody was listening to is never drawn as dead.
• Signal Alerts: frequency / threshold / duration rules that fire Discord and Telegram webhooks or auto-record.
• Logbook (ADIF): built-in ADIF logbook viewer with search, sort, and DXCC country enrichment. Two-way QRZ.com sync (Station Settings → QRZ Logbook, needs a QRZ XML subscription and a per-logbook API key) uploads new QSOs and downloads QRZ’s, with auto-upload and a manual Sync Now.
• Spectrum Snapshots: a gallery of captured waterfall snapshots.

Greyline Map: day/night terminator with operator location

A later moment as the terminator sweeps across

Band Activity: band-by-band activity over time, the trend, geography and a station table with click-to-tune

Propagation Map: Flat or Globe

New 2026-10. The propagation map has a Flat | Globe switch in its Layers panel. The globe draws everything the flat map draws on a 3-D Earth you can turn on any axis and zoom anywhere, and it covers the poles. The globe only loads the first time you pick it. The same map, with the globe, is on the desktop client and in the web client’s Map tab. New layers and settings:

• MUF: pick a band and the map shades where it should be open, from ShackLink’s propagation model run on the current sunspot number (it says it is a model, and which number it used).
• Greyline DX: paths with both ends in the greyline, the stations in it, and when the greyline opens and closes at your QTH and at a clicked point; ▶ play sweeps the clock forward.
• Ionosondes (measured MUF from KC2G, dimmed as each reading ages) and D-RAP, NOAA’s map of D-region absorption after a solar flare.
• Spot columns (globe only): the last 15 minutes of spots in each grid square, stacked by band.
• Hops (model) (globe only): each spot path drawn as equal hops off the ionosphere, clearly labelled a model.
• Satellites (AO-91, SO-50, the ISS and others, by the names operators use) with their orbits, footprints and next passes, and the Moon / EME window you share with a clicked point.
• City lights on the night side, and Worked DXCC, shading the countries of every entity in your whole log (approximate, and it says so).
• UTC or Local times and km or miles, plus map styles including satellite, street, topographic and dark.

The propagation map in Globe view, with the Layers panel open

Callsign Strip & UTC Clock

The callsign strip shows the operator callsign next to an NTP-synced UTC clock (shared by server and desktop client), with configurable layout, font, and colors. The same NTP-synced UTC clock also appears in the server and client window titles.

Rotary Frequency Knob & Memories

The frequency-entry popup is resizeable and includes a Freq-Knob rotary dial: an endless VFO knob with per-digit stepping and flywheel spin, the same shared SkiaSharp knob library that powers the photo panel’s Knob mode. The station’s 48 memories store frequency, mode and a label, page across the faceplate, and open in an All Memories grid for quick recall.

Frequency entry: keypad plus the rotary Freq-Knob for per-digit tuning

All Memories: all 48 channels as a resizable tile grid, click to recall, right-click to store / label / clear

Waterfall Painter (Spectrum Art)

The Waterfall Painter rasterizes text, an image, vector primitives, or an animation into audio tones across an SSB passband, so each tone lights one pixel column on a receiver’s waterfall: “waterfall art” drawn straight into the spectrum. Rehearse silently by painting into the Test Tone synth slot (every client sees it on the SDR stream), then transmit one-shot on air through the TX engine. It is SSB-only by physics: the sideband auto-follows the rig and there is deliberately no AM/FM (FM would smear the art).

The Waterfall Painter window: source, gamma, and passband controls

Rasterizing text into the passband

The art as received on the 2D waterfall

The same received art on the 3D terrain waterfall

Another camera angle on the received 3D art

Band Skimmer (Multi-Signal Decode)

A CW-Skimmer-style wideband decoder on the Tools tab. Instead of listening to one signal, it decodes every signal of a mode across a whole band segment at once (one decode lane per signal) off the raw I/Q of an SDR slot you already have running, and extracts callsigns into a live spot list. Point it at a slot, pick a band-plan preset or type a from/to range, tick the modes (CW, RTTY, PSK31 / PSK63, Olivia / Contestia, NAVTEX, FT8 / FT4 and Voice; with several ticked it classifies each signal and attaches the right decoder per lane), and hit Start. Each SDR slot can run its own skim, so several bands are skimmed at once. Because it taps the I/Q, it runs alongside the slot’s normal decoder and never touches the audio you’re listening to.

Confirmed callsigns show up as amber chips on the SDR waterfall (hover card + click-to-tune), spots feed the Band Activity dashboard and a session CSV, a watch-list callsign can fire a Discord / Telegram webhook, and stations you’ve worked before on the same band (from your ADIF log) are dimmed. The skimmer is server-owned, but the desktop, web, and mobile clients all show a live view console of the running skim: the same lanes, spots, and chips. CW copies best around 10–45 WPM; signals closer than ~50–75 Hz merge into one lane; FT8 / FT4 lanes are 3 kHz windows decoded by ShackLink’s own FT8 engine, while WSPR and JS8 are never skimmed, since WSJT-X and JS8Call decode those themselves.

The Band Skimmer: one decode lane per signal across a band segment, and the callsign spot list

Wideband Scan

Sweep one or several SDRs across a range far wider than any of them can see at once — a whole HF spectrum, every ham band, or the FM broadcast band — into a stitched panorama, a sweep-by-sweep waterfall, and a list of hits you can park a receiver on. Before anything moves, a preflight shows the hops, the sweep time, the resolution and the chance of catching a short signal, per radio. Frequencies that were not measured are drawn as gaps, never filled in. Keep one radio out as a listener so the search never stops while you listen, or as a classifier that visits each hit and labels its mode. The same engine runs Find stations. The desktop client can watch a scan live.

Wideband Scan: the stitched panorama, the sweep waterfall and the hits list

Voice Monitor

Live speech-to-text of the voice on the station’s own audio, with a streaming engine or a Whisper engine (optionally on the GPU), foreign speech transcribed in its own language, and optional live translation by a model that runs on this PC. Speech models download only when you agree. Transcription keeps running with the window closed. New 2026-10:

• On every client. The transcript and its translation reach the desktop, web and mobile clients, shown in the decoder display they already have while the station’s speech owns it. Watching starts nothing: the engines are switched on at the server.
• It survives a restart. The Voice Monitor keeps what it showed, colours included, and carries on from there after the server restarts; a reopened window picks up what was said while it was closed.
• Save transcript… and Load transcript… on the transcript menu, as rich text (keeping the colours) or plain UTF-8 text.

The Voice Monitor: the live transcript, one timestamped line per utterance

Scheduler

The Scheduler tab runs multi-step programs — tune, decode, record, transmit — once, daily, weekly, on an interval, or on demand. Programs chain together, start from built-in templates (CW Beacon, FT8 Session, WEFAX Receiver and test demos), and import and export as sets. A step can use an SDR slot as well as a rig, and a station step switches an antenna or powers the station up or down in order. Transmitting steps get band-plan checks, listen-before-transmit, a maximum TX time and automatic station ID.

The Scheduler: programs, their steps and their schedules

📡 Antenna Switching

The station’s antenna switch, its per-band memory, and a transmit interlock that refuses to key into the wrong antenna.

ShackLink can own the station’s antenna switch: which antenna each radio and each receiver is on, which antennas are legal on the band you are working, what the software remembers per band, and whether you are allowed to transmit at all. It is entirely server-side — the catalogue, the drivers, the memories and the interlock all live on the server, and no client ever talks to switch hardware or decides what is valid. A station with no switcher configured behaves exactly as it did before this feature existed.

The model

Devices are switch boxes, each with ports (a port feeds one radio or receiver) and positions (a position is one antenna socket). Antennas carry a name, a type, the bands they cover for TX and for RX, a receive-only flag, and the device / port / position they are wired to. Bindings attach a consumer — one of four rigs, or one of eight SDR slots — to a port, either as a claimant (it drives the switch) or as a plain consumer that only records which antenna feeds that receiver. That distinction is what lets a receive-only beverage on its own little switch follow an SDR slot’s tuning without ever touching the antenna your transceiver is using. Memories remember, per binding and per band, which antenna you chose.

Antenna Studio

Reached from the flight strip’s ANT cell, Antenna Studio has three tabs — Antennas, Bindings, Devices — plus a live diagram of the path from each consumer through its switch to the antenna currently selected. Antenna types are picked from a grid of seventeen technical elevation drawings rather than a list of words: wire dipole, inverted-V, end-fed, Yagi, hex beam, quad, log-periodic, vertical, trap vertical, whip, delta loop, magnetic loop, beverage, discone, dish, dummy load, and Unspecified. The Devices tab also carries switch discovery, the per-device Advanced editor, band-data output and storm park. On the Tools tab its tile is Antennas, Power.

Antenna Studio: the antenna table, the bindings and devices tabs, and the live path from each radio through its switch to the antenna

Eight driver families

Two things no driver here will ever do: there is no “toggle” anywhere in the subsystem — an antenna is always selected to an absolute position, because a toggle applied twice is a different antenna — and there is no pulse or flash timer, because a relay that opens again on its own is an antenna that changes by itself.

The TX interlock

Before every key-up the server checks the antenna path and refuses, in words naming both remedies, if the antenna is receive-only, has no TX rating on this band, the switch is disconnected, or the path is not confirmed. It covers all three ways of keying — text and CW modes, the Lab’s SDR transmissions, and voice, including a microphone or a footswitch, which is the likeliest way to put a carrier into a receive-only beverage.

Assumed is deliberately not an alarm — on a write-and-assume relay board it is the best answer that exists, and colouring it red everywhere would train the operator to ignore the colour. A switch in the middle of moving does not refuse either: the key-up waits for it, bounded, and only a timeout is an error. Aborting a 15-second FT8 cycle over a relay settle would be the wrong trade.

The interlock asks two questions, and for a long time it asked only one. It checked how fresh the reading was and never whether the reading agreed with the antenna you had selected — and the selection is recorded optimistically, at the moment you pick, before the driver is commanded. So a switch sitting on a different antenna passed with a perfectly fresh reading. Four routes went through that hole, the worst being a restart onto a switch somebody moved while the server was closed — keying into the receive-only beverage the other radio has claimed, which is the failure this whole subsystem exists to prevent. All four refuse now, and every refusal names a remedy that works: three of them used to end “or set this consumer to Manual”, which lifts nothing, and the unconfirmed-path one said “re-select the antenna” while re-selecting what you were already on was a no-op.

Every selection writes the whole relay bank

Reported as “clicking the antenna buttons makes several relays connected at the same time”. A relay driver used to write only the difference between what it believed the board was holding and what you had just asked for — and if the belief is wrong, that omits the break: the relay that really is closed is never told to open. Two antennas paralleled onto one feedline, or none, both a wrong load on the finals at full power, and every readback agreeing, because the board really is holding what it was last told.

Three separate routes to a wrong belief had each already cost a station — a command dropped on a write-only board, a readback that expired while the board was still moving, and somebody else changing the board (its own web page, a phone app, a second controller), which no care inside the driver can prevent. So the belief is gone: every selection writes every channel, and the cached word is not consulted on the write path at all. It costs nothing electrically — there is no toggle here, so a channel told the level it already holds does not move — and it buys self-healing, which a difference-only write cannot have. Note that the interlock had been refusing the whole time and the relays were still paralleled: a refusal is not a repair.

The confirmation poll had to slow down with it. Its interval came from the device’s settle time, default 15 ms — so a stock station re-opened a TCP connection to a Wi-Fi board every 20 ms for the whole confirmation window, and Tasmota answers requests from the same single loop that works its command queue. The wait was starving the switch it was waiting for, and a perfectly healthy selection came back blaming the wiring, the index base and the active-low setting, all three of which were correct. Each driver family owns its own poll interval now, and an operator who had already worked around this by raising the settle time keeps their setting.

When a switch will do nothing, it now says so

Three configuration mistakes used to leave a switcher completely inert while every readback agreed. An antenna with no relay word under a custom mask encodes to zero, so the board is told to energise nothing on every pick — a real station ran eight antennas that way. An antenna still on the park position is worse, because park is what a brand-new antenna is created on, so a station where nobody typed the position numbers has a switcher that is inert on every pick. And an antenna with no bands at all resolves to park for a Follow consumer while every picker greys it out, so the table looks right. Each now raises an amber banner on the Devices tab naming the antennas affected, and repeats itself where the decision is actually made — deliberately not on the link lamp, because “the cable is up” and “this configuration can select an antenna” are different questions.

Finding switches

Discovery has four ways of looking and only one of them asks: an Antenna Genius beacon, mDNS for Shelly boards, this machine’s serial ports — and a network scan, because whole families announce nothing at all. Tasmota, Modbus, the EA4TX RemoteBox and every classic relay board could previously only be typed in by hand. The scan is a separate press and the button names the subnet it is about to knock on: on the one discoverer that touches machines that are not yours, the caption is the consent. Its first pass writes nothing — a TCP connect and a close — and only the addresses that answer are asked which relay board they are. A probe may never be a write, which is enforced rather than intended: on this device class “it is only a GET, so it is safe” is false, because Tasmota’s control channel is a GET. A network wider than a /22 is refused in words rather than quietly truncated, since a silent cap reads as a completed search.

The manual switch

If the switch in your shack is a rotary knob on the desk, ShackLink still owns everything above it — the antenna table, the band coverage, per-band memory, the path diagram, the flight-strip cell and the interlock. Its contract is simply honest: nothing happened when we asked. A selection leaves the confidence Unknown, which the interlock has always refused; confirming that you turned the knob reaches Assumed, the permanent ceiling, so it is one confirmation per change rather than a nag on a timer. A reminder window lists the knobs that are unaccounted for — derived from your bindings, not from a queue of requests, which is what makes it right at session start, when every knob is unaccounted for.

Band data out

Two independent ways to tell the rest of the station what band you are on, both off by default. A binding can carry Yaesu 4-bit BCD band data on a device’s relays instead of an antenna — sharing a board with antenna positions, since the driver composes the bits on the way out and strips them on the way in. Or the server can emit the N1MM-format RadioInfo UDP broadcast on port 12060, the packet Green Heron Everyware, microHAM’s TRIO, the EA4TX RBM and the open ESP32/Arduino decoders already listen for. That one carries a frequency and lets the consumer decode the band, which is why it has none of the BCD holes — no 60 m ambiguity, no WARC merge, no vendor disagreement.

Band data is invisible to the TX interlock, and must be: an interlock refusal is about which antenna carries RF, and band data carries none. It is deferred under live TX, which is a different question — a relay moving under key is a hot switch of the amplifier’s input.

Receiving on a different antenna

New 2026-08-27. A binding can receive on one antenna and transmit through another — an RX-only Beverage for listening while the beam stays the transmit path. Only the transmit path guards a key-up; an unconfirmed receive antenna is a warning. Every client gains a Receive on choice once a second path exists, and a transmit change no longer drags a separate receive relay along with it.

Storm park

One latch grounds the feedlines: every claimant is parked, band-follow applies nothing, and a manual pick is refused in words. Since 2026-08-31 it can also disconnect everything, arm itself on a severe-thunderstorm or tornado warning for the station (US National Weather Service) and take the station’s mains down with it. The frequency is still recorded, so releasing lands on the right antenna without waiting for the dial to move. It is persisted, and that is the point rather than a convenience — a PC that reboots during a thunderstorm must come back parked. Arming it from a remote client is deliberately not offered: it is a safety action taken by somebody who can see the sky.

On every client

All five surfaces carry the antenna and none of them decides anything: the server console, the desktop client, the web client, the mobile app, and the Home Assistant radio card. On the two desktop apps the picker is the flight strip’s ANT cell — a duplicate row on the faceplate was retired in 2026-08, leaving exactly one antenna picker per window — and it is a panel of cards, a thumbnail of each antenna’s type beside its name and its switch port. A rig reaches one switch port, so its list is short; antennas on other ports are shown greyed under their own switch’s heading rather than hidden, because naming which antennas are out of reach is what tells you the binding needs changing. The row does not exist at all until the server says this rig is bound and the catalogue is non-empty — a station that has never configured a switcher gets no control, not a dead one. Nothing is applied optimistically: a client sends the pick and redraws only from what the server says actually landed, which is also what makes a refusal visible.

Two services that already knew everything about the station except this now know it too: MY_ANTENNA is stamped into every logged QSO when the rig is bound and something is selected, and two webhooks — antenna control stopped working, and something was refused permission to transmit — join the eight that already exist. Deliberately not “the antenna changed”: on a contest station that is a message a minute, and a notification stream nobody reads is worse than none.

⇄ Full Duplex

One named receiver keeps listening while the station transmits; every other receiver still goes deaf.

The satellite case is the headline: the rig works the uplink and an SDR slot hears the downlink. It also covers a second radio listening to a pile-up while you call, and hearing your own signal through a coupler. Arm it in Antenna and Automation Studio, or from the web client.

• Arming changes nothing on its own. The pairing is checked when you arm it and again at every key-up; if the receiver has been retuned or moved to another antenna in between, the transmission is refused rather than the receiver silently going deaf.
• A shared antenna is never allowed. Same-band pairings, unknown isolation and an unprotected receiver can be accepted, and your consent is recorded for exactly the transmitter, receiver, antennas and bands you were shown.
• Receive protection: a relay can take the receiver out of line (or pad it) before anything radiates, and nothing keys until it has confirmed it moved.

A station has transmitted and received at once, a protection relay has moved under a key-up, and the coupling between two real antennas has been measured. How much RF a given receiver survives has not been.

🌌 Multiband

Every streaming SDR slot on one stitched frequency axis, where a click tunes and listens.

Multiband puts every streaming SDR slot on a single stitched frequency axis — one spectrum and waterfall covering everything your receivers can hear, side by side in true frequency order. It is the Lab’s stitched axis promoted to an operating surface, and it runs on the server and the desktop client alike.

• Click anywhere covered → that slot tunes and you start listening to it. Ctrl+click tunes the rig instead.
• Wheel steps the station; Ctrl+wheel zooms; Ctrl+Shift+wheel moves the reference level; the arrow keys step the listened station.
• A click on a frequency nothing in the fleet covers is refused with the nearest covered edge named — never a silent nothing, and never an LO command, which would drag every decoder and skimmer riding that slot.
• A coverage ribbon puts the gaps the stitched axis hides back on screen in true scale, so 200 kHz of gap is distinguishable from 20 MHz of it.
• Signal-ID, skimmer and RDS chips render per slot, with the band plan, memory bank and DX spots. Anything in a stitched gap is skipped rather than snapped to a seam.
• LEVELS gives every band its own Trim (amplitude offset) and Cut (floor clamp), plus an RF gain column on the server. The shared axis’s Ref and Floor are deliberately not per band — one plot, one labelled dB scale.
• Activity dots, ribbon heat, fleet presets, a right-ear dual watch, and per-slot Identify Signals / Skim Callsigns quick-arms.

The page badges its amplitude axis rel and offers no markers, limit masks or dBm calibration — per-slot trims are live here, so a calibrated absolute number would be a lie. “Available on the control” is not the test; “correct on this page” is.

Multiband: every streaming slot on one stitched frequency axis, with the coverage ribbon underneath

🔄 Device Sync (Sync Tab)

Link rigs and SDR slots together so frequency and/or mode changes on one push through to another.

The Sync tab: four rig tiles and eight SDR slot tiles wired with rule arrows (amber dashed = automatic Track Rig)

The Sync tab lets you wire up rules between equivalent devices: OmniRig’s four rigs and the eight SDR slots (rig→rig, rig→slot, slot→rig, slot→slot). Useful for transverters (source on IF frequency, target on RF with a fixed offset), dual-radio diversity setups, a monitoring receiver or panadapter that should always track the main rig, or making one SDR’s Lab trace follow another. For rigs a rule reads/writes VFO-A; for SDR slots it reads/writes the slot’s LO / center frequency (in-span demod retunes don’t fire rules).

Creating a Rule

1. Open the Sync tab: you’ll see four rig tiles (Rig 1 – Rig 4) and eight SDR slot tiles (S0 – S7, empty slots dimmed)
2. Drag between any two tiles. An arrow appears representing the rule.
3. Click the arrow to select it. The rule’s properties appear on the right.
4. Build chains by adding more rules (Rig 1 → Rig 2 → Slot 3): a change at the head applies to every hop in one pass. Bidirectional pairs and accidental cycles are safe: each device is written at most once per change.

Per-Rule Properties

• Offset: Frequency offset (MHz) added to the source before writing to the target. Can be negative. Typical use: transverter IF offset.
• Invert Sideband: USB↔LSB, CW-U↔CW-L, DIG-U↔DIG-L. Applied when Sync Mode is on.
• Sync Frequency: Copy source frequency (+ Offset) to target (rig VFO or slot LO).
• Sync Mode: Copy source mode (optionally inverted) to target. Rig→slot maps onto the slot demodulator; slot→rig maps the demod mode back.
• Enabled: Per-rule on/off, disables without deleting.

Automatic Rules

SDR slots with Track Rig on show an amber dashed AUTO arrow from the currently selected rig, the rig-tracking mechanism made visible. Auto rules are read-only; deleting one turns Track Rig off for that slot. Slot tiles carry AUD (audio-active), TRK (Track Rig) and IF (IF-mode panadapter, LO pinned) badges.

Global Enable + Logic

The Enable Sync toggle at the top right is a master kill switch for the whole engine. For a change on the source device to propagate to target, three conditions must all be true:

1. Global Enable Sync = on
2. Per-rule Enabled = on
3. At least one of Sync Frequency / Sync Mode = on

The engine separates genuine changes from its own echoes by value (a device reporting back the value just written to it is ignored), rate-limits each rule to ~3 writes/s, and cuts rule cycles deterministically (each device written at most once per change). Rules targeting a rig-tracking or IF-locked slot are skipped (those mechanisms own that slot’s LO); a tracked slot’s machinery moves don’t fire its outgoing rules. Manual moves do. All rule data (offsets, toggles, enabled states, global enable) is saved automatically on every change and restored on the next run.

📋 System Requirements

What you need to run ShackLink Server and clients.