SigDigger Console — SDR Field Guide for Elliott Bay

TL;DR — what it actually is

Stack

Frontend: Qt5/C++ (OpenGL waterfall)
DSP core: sigutils + Suscan (multicore-aware)
Hardware abstraction: SoapySDR
License: GPL-3.0
Author: Gonzalo José Carracedo Carballal
Repo: BatchDrake/SigDigger

What you get

Real-time spectrum & waterfall, OpenGL-accelerated
AM, FM, LSB, USB analog demod
ASK / FSK / PSK inspectors with blind parameter estimation
Doppler analysis & Analog TV demod
Baseband recording — full spectrum and per-channel
Network broadcast of demodulated channel data
UDP broadcast of received samples and demodulated symbols

Hardware matrix — what to feed it

SoapySDR is the abstraction. Anything with a Soapy module shows up as a device. The shortlist that's actually useful for the Salish Sea:

Device	Range	Bandwidth	Cost (USD)	Salish use
RTL-SDR Blog v4	500 kHz – 1.75 GHz	2.4 MS/s	$30–40	Marine VHF, AIS, NOAA WX, ADS-B
Airspy HF+ Discovery	0.5 kHz – 31 MHz / 60–260 MHz	768 kS/s	$169	HF maritime, low-VHF, very low noise
Airspy R2 / Mini	24 MHz – 1.8 GHz	10 MS/s	$99–169	Wide marine + aero look-down
HackRF One	1 MHz – 6 GHz	20 MS/s (8-bit)	$300–340	Half-duplex TX for testing your own LoRa node
SDRplay RSPdx	1 kHz – 2 GHz	10 MHz	$250	Long-wave to UHF, good preselectors
KrakenSDR	24 MHz – 1.766 GHz × 5 ch	2.56 MS/s × 5	$700	Direction-finding on AIS / vessel emitters
LimeSDR Mini 2.0	10 MHz – 3.5 GHz	10 MHz	$420	Full-duplex, narrowband nicer than HackRF

For whale calls specifically

Cetacean vocalizations live 10 Hz – 25 kHz (orca sits in ~500 Hz – 25 kHz; blue/fin/humpback < 1 kHz). That's audio band, not RF. SigDigger is for the radio side — picking up the infrastructure around the whales (ferry AIS, NOAA WX, marine VHF chatter, Coast Guard P25). The actual hydrophone signal lives in the iPhone node and the LoRa buoy.

Frequency tour — Elliott Bay, north to Alki

The bands worth parking on while you watch the bay. All numbers in MHz.

Band	Freq (MHz)	Mode	What you hear
NOAA Weather (KHB-60)	162.550	NFM	Seattle marine forecast, sea-state
AIS Channel A	161.975	GMSK 9600	Vessel position, cargo, MMSI
AIS Channel B	162.025	GMSK 9600	Mirror — listen on both
Marine VHF 16	156.800	NFM	Distress & calling — always on
Marine VHF 13 (Ch 13)	156.650	NFM	Bridge-to-bridge, ferry traffic
Vessel Traffic Service	156.250 / 156.700	NFM	Puget Sound VTS sectors
USCG Sector Puget Sound	~169 / 171	P25 Phase 1	SAR, escort tasking
SeaTac approach	119.200 / 120.400	AM	Aircraft over the bay
SeaTac ADS-B	1090.000	PPM	Decode with `dump1090` in parallel

Install — one command per OS

macOS (Homebrew)

# SoapySDR + SigDigger via the SDR-on-Mac tap
brew install --cask sigdigger
brew install soapysdr soapyrtlsdr soapyhackrf soapyairspy
SoapySDRUtil --probe

Ubuntu / Debian

# Build from source — pre-built debs lag a few months
sudo apt install build-essential cmake qtbase5-dev libsndfile1-dev \
                 libsoapysdr-dev soapysdr-module-rtlsdr soapysdr-module-airspy
git clone --recursive https://github.com/BatchDrake/SigDigger
cd SigDigger && ./build && ./build/SigDigger

Windows

Grab the latest portable zip from the releases page, unzip, run SigDigger.exe. Plug in the SDR before launching so Windows binds the WinUSB driver via Zadig.

Network broadcast — the headless pattern

The trick that makes this useful for a whale-watching deployment: run the SDR at the dock on a Pi 5, broadcast its samples to your laptop on the couch via UDP, and only haul the Qt UI when you want to look at the waterfall. SigDigger speaks VITA-49-ish UDP and SoapySDR's remote modules.

   ┌──────────── PIER 70 ────────────┐         ┌────── HOME OFFICE ──────┐
   │  [RTL-SDR v4] ─USB─ [Pi 5]      │         │                         │
   │                  │              │         │     ┌──────────────┐    │
   │     soapy_remote │ rx_sdr ──── UDP/9999 ────────►│  SigDigger   │    │
   │                  │              │  Tailscale     │  (waterfall) │    │
   │     dump1090 ────┴── tcp 30005 ─┘  WireGuard     └──────────────┘    │
   │                                 │  or LAN              │             │
   │                                 │                      ▼             │
   │                                 │              ┌──────────────┐      │
   │                                 │              │  recordings/ │      │
   │                                 │              │  *.cf32      │      │
   │                                 │              └──────────────┘      │
   └─────────────────────────────────┘         └─────────────────────────┘

Pi-side: expose the dongle as a Soapy server

# Headless Pi at the dock — run as a systemd unit on boot
sudo apt install soapyremote-server soapysdr-module-rtlsdr
SoapySDRServer --bind=0.0.0.0:55132

Console-side: connect SigDigger to the remote

# Source > Add device, then in "driver" field:
driver=remote,remote=tcp://pier70.tailnet:55132,remote:driver=rtlsdr

Or: pure UDP sample firehose

# suscli — Suscan CLI shipped with SigDigger
suscli devices                          # list whatever SoapySDR sees
suscli profile new bay --device 0 --rate 2400000 --freq 162025000
suscli broadcast bay --remote 192.168.1.42:9999 --proto udp

Operator's checklist — Elliott Bay watch

Mount the antenna outside. Elliott Bay has a clear water shot from Alki, Magnolia, and the West Seattle bluff. A discone or a 1/4-wave whip on the rail is enough for marine VHF / AIS. Avoid the elevator shaft.
Park on AIS first. AIS gives you ground truth — every cargo, ferry, tug, and most pleasure craft self-reports position, course, speed. DSC + AIS at 161.975/162.025 feeds the fusion layer downstream. Use SigDigger's PSK inspector or aisdecoder.
Then NOAA WX. 162.550 MHz, NFM, ~12 kHz wide. Loud, ever-present, useful for sea-state correlation against orca presence.
Doppler-watch ferries. Ferries on the Bremerton/Bainbridge runs are big underwater noise sources. Their VHF Ch-13 calls give you the schedule. Tag those clips and feed them to the fusion layer.
Record everything as cf32. Disk is cheap, your time is not. SigDigger's full spectrum baseband recording means you can re-demod weeks later when you realize that pop at 12:42 was a hydrophone pulse, not background.

Why SigDigger and not the alternatives

vs. GQRX

GQRX is GNU-Radio-based and is fine for "where's the carrier." SigDigger has the inspector pattern — you can drop a chunk of waterfall onto a constellation diagram and let it estimate baud + symbols blind. That's the difference.

vs. SDR#

SDR# is Windows-only, closed-source, and has plugin licensing weirdness. SigDigger is GPLv3 across all three OSes and scriptable from the CLI.

vs. CubicSDR

CubicSDR is great for casual listening and easy install. It does not have Suscan's blind-modem inspector, multi-channel demod recording, or the UDP sample broadcast that this rig depends on.

Where it fits in the stack

Node 02 · Telemetry ESP32 + LoRa Whale Buoy → Node 03 · Acoustic iPhone Hydrophone Stream → Node 04 · Fusion Salish SIGINT Mesh →

Salish SIGINT · Node 01 / 04 SigDigger by BatchDrake · GPL-3.0 · this writeup CC-BY-SA

SigDigger as your operator consolefor the Salish Sea.