💡 Key Features

🛠 Installation

💾 Memory & Modes

Memory Buttons

24 programmable memory slots synced with the server in real-time:

• Quick click – Recall saved frequency and mode
• Long press (1 second) – Save current frequency and mode to that slot
• Right-click – Clear a programmed slot
• Labels – Custom labels can be assigned via the “All Memory Slots” dialog
• Active memory – Highlighted when current frequency and mode match
• All Memory Slots – Click the “All Memories” button for a scrollable grid with inline label editing

Memory contents are stored on the server and synchronized with all connected clients. Changes from any client (desktop, web, mobile, or HA) appear on all others instantly.

Audio Tab — Visualization & Recording

The Audio tab renders the received audio as a live waterfall / spectrum / oscilloscope / spectrum-LED display with six themes, peak-hold, and gain / contrast / range sliders. When the stream is stereo (HiFi MP3 or WFM), the display splits into dual L/R channels.

SDR Panadapter

The SDR tab connects to the server’s spectrum stream for real-time waterfall and spectrum display:

• Multi-SDR slot selector – When the server has multiple SDR devices active (up to 8), a Slot dropdown and Audio button appear. Select a slot to view its spectrum; press Audio to switch the listening source. Hidden when only one device is active.
• Slot kinds – Some slots are not frequency-agile the way a normal SDR is: a native Icom CI-V scope slot and an IQ-file playback slot (a looped recording) have a fixed LO, so drag-to-pan — and, for Icom, the FFT-size and Zoom-FFT controls — are disabled, and click-to-tune moves the demodulator listen point instead of re-centering the capture. (IQ-file slots keep the FFT size adjustable.)
• Embedded display – Scope + waterfall on the SDR tab
• Popout window – Separate resizable window via “Popout Spectrum” button
• Click-to-tune – Click on the waterfall to change the rig frequency (routed to the selected slot)
• Memory markers – Optional frequency markers from stored memories
• DX spot markers – Live DX cluster spots drawn on the waterfall with callsign labels
• Broadcast station markers – Known broadcast station frequencies overlaid with station name labels
• Navigator overview – Miniature full-band view showing the current zoom window position with rig frequency line
• Peak markers – Configurable markers on the strongest spectrum peaks (count, color, size, style, frequency labels)
• Reverse waterfall – Flipped layout with upward scrolling (waterfall on top, scope on bottom)
• Palette – 8 waterfall color palettes, unified with the Lab tab: Classic (blue), Classic (green), CoolWarm, Viridis, Plasma, Inferno, Grayscale, Neon (cyan)
• 3D waterfall (terrain view) – Toggle the waterfall pane between the flat 2D view and a rotatable 3D perspective terrain (right-click → “3D Waterfall”, or the corner 3D/2D button). Drag to orbit the camera (pitch/yaw), right-drag to pan vertically, with “Reset 3D View” and an optional “Fit Height to Pane”. GPU-accelerated (SkiaSharp / OpenGL) with a silent CPU fallback; colors and heights match the 2D waterfall exactly
• Waterfall Ref (max-level) slider – Sets the top of the waterfall color scale (dBFS) so strong signals reach the top (“red”) of the palette instead of being clipped below full scale
• Phosphor histogram mode – An optional, experimental GQRX-style histogram / density spectrum color mode alongside the existing amplitude-hue, density-palette, and Gaussian-spread phosphor modes
• Auto-discovery – SDR stream port discovered via UDP broadcast

Lab Measurements (RF Workstation)

The Lab tab provides a professional-grade RF measurement workstation, identical to the server’s Lab tab. All code is shared — the client receives SDR spectrum data from the server via the existing SDL1 binary stream and feeds it into the same multi-trace analysis engine.

Traces (up to 8)

Each trace binds to an SDR slot and applies independent processing:

• Trace modes — ClearWrite (live), MaxHold (peak envelope), MinHold (noise floor), Average (configurable N), RMS
• Per-trace controls — visibility, color, peak-hold color, label, source slot, gain offset (−60 to +60 dB), noise floor (−160 to −20 dB)
• Math traces — A+B and A−B operations between any two traces for comparison and delta measurements
• Source routing — each trace can be bound to a different SDR slot, enabling multi-device overlay comparisons
• No-data legend status — a checked trace whose SDR source isn’t delivering data still appears in the legend, its name dimmed with a short status word (“Not started”, “No data”, or “Unavailable”) in place of a frequency range, so you can see it’s selected but waiting on its device

Markers (up to 8)

• Normal — frequency and amplitude readout at the marker position
• Delta — frequency and amplitude difference between two markers
• Band Power — integrated power within a specified bandwidth around the marker
• Noise — noise density (dBFS/Hz) at the marker position
• Peak search — jump to the highest peak, navigate to next peak left/right, or find the minimum
• N-dB bandwidth — find the −3 dB (or configurable N) bandwidth around a peak. Dropdown selects 3/6/10/20/40/60 dB
• Click-to-place — click on the spectrum display to place the next marker at that frequency
• Clear All Markers — the spectrum right-click menu (next to “Place Marker Here”) removes every placed marker and clears the marker grid in one step

Tune From Spectrum & Band Browse

By default the Lab is a passive overlay, but enabling Tune From Spectrum (spectrum right-click menu) lets the Lab drive listening and tuning — it still never alters the SDR capture pipeline or FFT:

• Select a trace — click a trace to highlight it and switch audio-follow to that SDR slot (you now hear that device)
• Tune the listen point — click again within the selected trace’s band to tune that slot’s demodulator to the clicked frequency. This moves the listen point only — it does not re-center the SDR LO, so the trace stays put
• Overlays — the selected trace can show a VFO frequency readout (“Show Frequency”) and a passband box (“Show Passband”)
• Peak markers — mark the top-N peaks on the selected trace; the “Peak Markers” submenu configures count (3–10), color, size (2–8 px), style (filled circle / outline / square / diamond), and optional frequency labels
• Band Browse — grab a trace line and drag horizontally, or click the plot then press Left/Right arrow keys, to shift that slot’s LO across the band (Shift = ×10 coarse, Ctrl = fine step). For the audio-active slot the absolute listen frequency is held by compensating the demod offset; audio mutes when that frequency leaves the captured span and resumes when a later shift brings it back. Refused for rig-tracking slots and IF-panadapter mode (a brief on-display “Locked” notice)
• Shift Station to Edge — from the spectrum right-click menu, park the selected trace’s tuned signal at the left or right edge of its span (the server computes the LO from the listen frequency and demod mode). Pair a “Right” on a lower trace with a “Left” on a higher one for a side-by-side stitched view of two signals

Automated Measurements

An eight-row Measurements grid (a label tab beside Markers) computes a measurement per trace every sweep, with blank-for-auto parameters and live Result/Detail columns; a quick readout also appears in the toolbar:

• Channel power — total power within a defined channel bandwidth
• Occupied bandwidth (OBW) — bandwidth containing 99% of signal power
• ACPR — adjacent channel power ratio
• SNR — signal-to-noise ratio
• Harmonics / THD — harmonic distortion analysis
• IMD / IP3 — intermodulation distortion and third-order intercept point
• CFO — carrier frequency offset vs a reference, in Hz and ppm
• Occupancy — percent of a band above the noise floor, averaged over a time window
• Duty cycle — percent of time a channel is keyed over a window
• Envelope — peak / current / floor at a frequency, held across sweeps
• ImageRej — I/Q image rejection: a signal versus its mirror across the receiver’s DC, in dBc
• NoiseRise — close-in noise floor near a strong carrier versus the far floor (reciprocal-mixing proxy)
• SpurMask — spurs as dBc below the carrier against a simplified ITU-R SM.329 mask, with a PASS/FAIL count
• Flatness — spectral flatness (Wiener entropy) over a band, with passband ripple

A Log to CSV toggle appends every enabled measurement row to %LocalAppData%\ShackLink\Lab\measurements.csv (about once per second) for trend plotting. Readings are relative (dB/dBFS/dBc/%/Hz) unless you supply a per-slot calibration (see below), in which case the absolute power readouts can show approximate dBm*.

Amplitude calibration (approximate dBm)

Consumer SDRs have no traceable power calibration, so the Lab is relative (dBFS) by default. You can assert an approximate absolute reference per SDR slot: switch the amplitude unit to dBm, then either type a per-slot offset directly or, with a marker on a known signal, type its level in the Cal drop-down and click Set from marker (offset = known dBm − marker dBFS). Absolute readouts (channel power, noise floor, envelope, marker amplitude, cursor) then show dBm* — the * marks it as user-asserted and not traceable. Relative metrics (SNR, ACPR, image rejection, flatness, …) are unaffected. The calibration is tied to the slot’s gain: any gain change (MGC / LNA / AGC, and conservatively IF gain) marks it stale and the slot reverts to dBFS until you re-set it — so a stale offset can never silently lie. Calibration applies on both the server and the (remote) desktop client; the server broadcasts a per-slot gain-change pulse so the client invalidates too.

Display Modes

• DPX persistence — temporal density display showing signal persistence over time. 8 color palettes (unified with the SDR tab): Classic (blue), Classic (green), CoolWarm, Viridis, Plasma, Inferno, Grayscale, Neon (cyan)
• Spectrogram waterfall — time-frequency display with gain, contrast, floor, and speed controls. Synced frequency axis with the main spectrum display
• 3D waterfall (terrain view) — the spectrogram waterfall can toggle into a rotatable 3D perspective terrain using the same shared renderer as the SDR tab: orbit-drag the camera, “Reset 3D View”, optional “Fit Height to Pane”, GPU-accelerated with a CPU fallback
• Spectral CCDF — complementary cumulative distribution of spectrum-bin amplitude relative to the mean (a frequency-domain distribution and spectral peak-to-mean ratio, not time-domain PAPR / crest factor — that would need raw I/Q the Lab never receives)
• PSK constellation + EVM/MER — live I/Q scatter of recovered PSK31 symbols (2 points BPSK-31, 4 QPSK-31) with persistence, ideal-point overlay, and a genuine modulation-quality readout (Error Vector Magnitude %, Modulation Error Ratio dB). The server computes the metric and streams the symbol cloud, so the remote client sees the same scope. PSK31-only; shows “—” (never a fake 0 %) when no PSK31 signal is locked. A VSA summary adds peak EVM, a magnitude/phase-error split, residual carrier frequency error (after AFC), and I/Q offset, with a 60-second EVM trend
• Audio SINAD — true signal-to-noise-and-distortion ratio of a steady tone (CW/SSB beat-note, AM/FM tone, or test tone) in the demodulated audio of the SDR slot you are hearing. Measured from the real demod audio rather than the spectrum, computed on the server and broadcast to the client; a ratio, so no calibration needed; shows “—” honestly when no tone is present
• Navigator bar — optional Trace or Waterfall-history overview showing the zoom position within the full span

Instruments (Dedicated Measurement Windows)

The Instruments toolbar dropdown opens focused, single-purpose measurement windows that run alongside the analyzer — the same suite as the server’s Lab:

• Modulation Analyzer — an analog modulation meter for the slot you are hearing: AM depth, FM deviation (peak / RMS), carrier offset, and modulation rate on a needle face. Measured on the server from the demodulated audio and broadcast to the client; AM/FM only; honest “—” with no carrier
• Phase Noise — carrier-tracked SSB phase noise L(f) dBc/Hz vs log offset, with a decade table (10 Hz–1 MHz), integrated jitter, spur exclusion, window-skirt masking, and reference save/compare. Pure trace math, computed locally (the server broadcasts which FFT window is in use so the dBc/Hz is correct)
• Noise Figure — a guided Y-factor noise-figure wizard with a calibrated noise head: system NF (Mode A) or DUT NF + gain via Friis (Mode B), NF(f)/gain(f) curves, ENR head profiles, and gain-change voiding. Pure trace math, runs locally
• Mask Trigger — a view-only event console for the server’s frequency-mask trigger: armed masks, the event list, and the slot timeline. Arming and the black-box I/Q capture happen on the server

The Zero-Span Scope and the video record button are server-only and not shown on the client (both need the server’s raw sample stream or its native capture component). Everything else in the Instruments menu works over the network.

Advanced Features

• Transfer function (S21) — two-SDR stimulus/response measurement with limit mask overlays for compliance testing
• Limit masks — regulatory and user-defined spectral masks (spurious emission, harmonic suppression, bandpass)
• C# scripting — Roslyn-based scripting engine with full MeasurementApi for automating measurements, sweeps, and data collection
• Export — CSV (all traces), Touchstone S1P/S2P, PNG screenshot, and measurement log
• Cable loss compensation — predefined cable types (RG-58, RG-174, etc.) and custom entry for length-based loss correction

Toolbar Controls

The Lab toolbar provides: Popout button, Reset Zoom, Start/End frequency entry with Auto-Range toggle, peak/min search and navigation, reference level and display range, N-dB bandwidth selector, DPX toggle, waterfall toggle with palette selector, transfer function dialog, limit masks, script editor, CSV export, screenshot, a live measurement result readout, an amplitude unit selector (dBFS / dBm), and a Cal drop-down for per-slot approximate-dBm calibration, and an Instruments dropdown that opens the dedicated measurement windows (Modulation Analyzer, Phase Noise, Noise Figure, and the Mask Trigger event console). Waterfall gain/contrast/floor sliders appear when the spectrogram is visible.

Popout Window

The Popout button opens a separate resizable Lab window with its own independent MultiTraceDisplay, SpectrogramDisplay, and CcdfDisplay instances. Both the tab and the popout share the same TraceEngine and MarkerEngine — trace data and marker updates flow to both simultaneously. A Link toggle controls the relationship: when linked (the default) the popout mirrors the tab and display settings (zoom, ref level, palette, 3D camera, panes) sync bidirectionally; when unlinked the popout becomes fully independent with its own zoom, scale, palette, 3D camera, and pane layout, persisted separately. The popout window position and size are saved between sessions via PopoutSettings.

Persistence

The entire Lab session state is saved to %LocalAppData%\ShackLink\lab_session.cfg and restored on startup: all 8 trace configurations (source, mode, colors, gain, floor), all 8 marker states, display settings (frequency range, reference level, display range, DPX enabled, palette), spectrogram settings (gain, contrast, floor, speed), splitter positions, waterfall/CCDF trace indices, the amplitude unit, and per-slot calibration offsets (valid ones only — a gain-staled offset is dropped).

Connect / Disconnect

The Connect button stays enabled after connecting and changes to “Disconnect”, allowing manual disconnection from the server. Server IP and port fields lock while connected.

Mode Selection

The mode dropdown allows selecting the operating mode:

• USB – Upper Sideband
• LSB – Lower Sideband
• CW – Continuous Wave (Morse)
• FM – Frequency Modulation
• AM – Amplitude Modulation
• RTTY – Radio Teletype
• DIG – Digital modes

Digital Decoder Panel

• Decoder Mode – Select CW (Morse), RTTY, PSK31, FT8, SSTV, WEFAX, NAVTEX, or APRS from the buttons. The choice is broadcast to every connected client — switching mode here switches the server tab and every other client too.
• Enable/Disable – Toggle decoding subscription
• Decoded text – Shows characters as they are decoded (CW / RTTY / PSK31 / FT8)
• Image + waterfall – SSTV / WEFAX panels show the decoded image on the left and a live waterfall of the audio band on the right with a draggable splitter. Slant / shift sliders correct alignment drift.
• Signal scope – Visual display of audio signal (CW mode)
• Clear button – Clear the decoded text display
• Save button – Save decoded text to a file (image modes save the image)

TX Tab — CW, Voice & Digital

The TX tab hosts the QSO chat panel for the text and voice modes. Everything is driven through the server’s TxEngine under a single-owner lock; a Test (no RF) switch lets you rehearse offline.

TX Tab — Image Modes (SSTV / WEFAX)

When the TX-mode picker selects SSTV or WEFAX, the chat panel swaps in an ImageTxPanel:

• Pick mode (SSTV: 18 sub-modes; WEFAX: IOC + LPM)
• Choose Image — the panel resamples and shows a preview
• Click Send — image is uploaded to the server (chunked, SHA-256 verified, 5 MB cap), encoder runs, PTT keys via OmniRig, live build-up shows in the preview as the encoder transmits
• Test (no RF) mode (chat panel header): encoder runs but PTT stays low — for offline rehearsal. A WAV is saved next to the source image.
• Other connected clients see TX:STATUS and TX:PROGRESS so they can follow the line counter

FT8 Color Coding

FT8 messages are color-coded by signal strength (SNR) for easy identification:

SNR Range	Color	Signal Quality
0 dB and above	Bright Green	Strong signal
-10 to -1 dB	White	Moderate signal
-15 to -11 dB	Orange	Weak signal
Below -15 dB	Red	Very weak signal

Band Plan Table

Access the amateur radio band plan with frequency allocations:

• Open – Click the Band Plan button to open the frequency table
• Click to tune – Click any entry to tune the radio to that frequency
• Auto-highlight – The table automatically highlights the matching entry when the radio frequency changes
• Session persistence – Window position and open state are remembered between sessions

The band plan includes calling frequencies, band edges, and mode allocations for all amateur bands.

🔧 Troubleshooting

Cannot Connect to Server

• Verify the server is running and accessible
• Check the IP address and port are correct
• Ensure no firewall is blocking the connection
• Try pinging the server IP from command prompt
• If using auto-detection, try enabling “Force IP” mode

No Audio

• Ensure the Audio button shows a green checkmark (indicating streaming is active)
• Check system volume and ensure speakers are not muted
• Verify the volume slider in the client is not at zero
• Check that audio streaming is enabled on the server
• Note: Audio state is saved between sessions – if you had audio enabled last time, it will auto-start on connect

Radio Shows Offline

• Verify OmniRig is running and connected to your radio
• Check the radio is powered on and communication cable is connected
• Restart OmniRig and reconnect from the server

Application Won’t Start

• Ensure .NET Framework 4.7.2 or later is installed
• Try running as Administrator
• Check Windows Event Viewer for error details