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inspectrum

v0.4.0 open-source

inspectrum is a tool for analysing captured signals, primarily from software-defined radio receivers.

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Summary

inspectrum is an open-source desktop application for analysing signals captured from software-defined radio receivers, free to use and run locally as a Qt-based GUIGUIA graphical user interface, controls such as windows, buttons and menus. It lets people use software visually rather than entering commands. on Linux, macOS, or Windows. It reads large captures (100GB+) in formats like SigMF, GNU Radio's cfile, and vendor-specific formats from HackRF, BladeRF, and RTLRTLRegister Transfer Level, a hardware design abstraction describing how data moves between registers each clock cycle; cyber tools use it to analyze or synthesize digital circuits from HDL source.-SDR, presenting a zoomable spectrogram alongside amplitude, frequency, phase, and IQ plots, with cursors for measuring symbol rate and extracting symbols for export. This makes it a fit for RF engineers and signal-intelligence researchers doing manual, visual analysis of captured traffic rather than automated decoding pipelines. It sits in the SDR signal-analysis space alongside general tools like GNU Radio and Universal Radio Hacker, though it focuses narrowly on inspection rather than transmission or protocol reversing. First committed in 2015 and still maintained, with 42 contributors and a release roughly eight months ago.

inspectrum is a tool for analysing captured signals, primarily from software-defined radio receivers.

How inspectrum helps

Where in this capture does a signal of interest actually start and stop?

the zoomable, pannable spectrogram lets you scan across hours of samples visually and pinpoint the exact time range, without decoding anything first

What is the symbol rate of this unknown transmission?

cursors placed across repeating features in the amplitude or frequency plot measure the period directly off the waveform, giving a rate you can feed into a demodulator later

Is this modulation ASK, FSK, or something with phase shifts?

the amplitude, frequency, phase, and IQ plots of the same selection are viewed side by side, so the shape that jumps out under each view points to the modulation family

Can this multi-gigabyte capture from my SDR be opened without running out of memory?

files are read from disk rather than loaded wholesale, so 100GB+ recordings in SigMF, cfile, or vendor formats from HackRF, BladeRF, and RTL-SDR open and scroll without exhausting RAM

What are the actual bits behind this burst I've isolated?

symbol cursors laid across the selected region extract the underlying symbols for export, turning a visual pattern into data for further decoding

Which segment of this recording is worth exporting for a colleague or another tool?

a selected time span, filtered samples, or demodulated data can be exported on its own, rather than handing over the entire original capture

all 5 features, with the evidence for each →

Languages

Not documented

Features

5 capabilities

Built from inspectrum's releases, docs, README and our own runs. “Seen” marks the month we first spotted a release the vendor didn't date.

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All capabilities 5 capabilities
Data export shipped Enables exporting visualized signal data for external analysis or documentation. 1 release · 1 other source · first seen Feb 2017

release

example

  • Export the visualized signal data for external analysis or documentation. Use the 'data export' option from the view menu to save the current plot state v0.2 · Feb 2017 · source
Interactive cursor markers shipped Allows placing cursors on time-domain plots to identify signal boundaries. 2 releases · first seen Feb 2017

release

  • Enables symbol extraction using cursor positions to identify signal boundaries v0.2 · Feb 2017 · source · release history
  • Adds cursors for placing markers on the time-domain plot v0.2 · Feb 2017 · source · release history
Real-valued sample support shipped Enables import of real-valued signal data in addition to complex samples. 1 release · first seen Dec 2020

release

Enhanced plot types shipped Adds plotting capabilities for IQ samples, amplitude, frequency, and phase data. 1 release · first seen Feb 2017

release

  • Introduces additional plot types for IQ samples, amplitude, frequency, and phase data v0.2 · Feb 2017 · source · release history
Multi-format file import shipped Supports importing sc8, uc8, and sc16 file formats for signal analysis. 1 release · first seen Feb 2017

release

Lines in monospace are the tool's own words: help text parsed from its source, or an endpoint from its API document. Under release, a line is our summary of a dated release. Under docs, it is quoted from the tool's own documentation or website. Each links back to the source it came from.

Score card

  1. Shipping velocity releases a month, last 12 months
  2. Documentation quality release-notes rubric, 0–100
  3. Breaking-change discipline how rarely a release breaks users, and notice given
  4. Maintenance risk quiet time against its own cadence, maintainers
  5. Innovation & surface new capabilities, API and MCP surface
  6. Community health
  7. Contributor trend distinct committers, this year against last
  8. Maintainer concentration bus factor now against a year ago
  9. Issue backlog trend issues closed per issue opened, 12 months
  10. Responsiveness median time to a maintainer’s first reply

Nine scores for inspectrum, each built from the releases, notes and API history this site tracks — and, on Researcher and Business, where it stands among every measured tool in its category and how that has moved.

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Each score is 0–100 on a published rubric, derived from data this site already shows. A dimension we cannot measure says so — it is never scored 0 and never enters a rank.

How this is scored
  • Shipping velocity — releases a month over the last 12 months, on a log scale where 16 a month scores 100. Needs 3 releases in the window.
  • Documentation quality — the release-notes rubric published on the analytics page, unchanged.
  • Breaking-change discipline — the share of releases carrying a breaking change (none scores 100, half or more scores 0). Only projects that label breaking changes are measured: a clean record cannot be told from an unlabelled one.
  • Maintenance risk — quiet time measured against the tool's own release cadence (quiet longer than 90 days and three typical gaps scores 0), plus the number of active maintainers and whether contributors are growing, where known. Higher is lower risk.
  • Innovation & surface — new capabilities in the feature ledger this year, API and MCP operations added, and the share of commits that are features: the mean of whichever we hold.
  • Community health (open-source tools only) — each is a direction, not a size: contributors this year against last, the bus factor now against a year ago, and issues closed per issue opened, where steady scores 50, doubled 100 and halved 0; plus the median time to a maintainer's first reply (an hour scores about 100, a month or more 0). A commercial card has no repository and carries none of the four.
  • Documented delivery (commercial tools) — when a vendor's documented new capabilities have slowed against its own baseline, that counts against the overall standing as heavily as two low dimensions. Steady delivery, or too little history to judge, leaves the standing alone; it is never a sixth score.
  • Open-source tools are scored on repository signals; commercial tools on their published changelog. Ranks compare tools within one category and one profile and need at least five measured peers; the overall standing needs three ranked dimensions. Best-in-breed or consolidator is a shape, not a quality, and is never scored.

Release-note detail over time

See how much detail inspectrum puts in its release notes, quarter by quarter, and compare it with tracked tools in the same category. This history uses up to ten retained, reviewed notes per tool; sparse or blank older quarters may reflect that limit.

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Releases

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3 entries

  1. December 20251
  3. December 20201
  5. February 20171
    Show

    3 entries

    1. v0.4.0 Dec 6, 2025 · release notes

      inspectrum v0.4.0 adds Qt 6 support and SigMF dataset ingestion for RF signal analysis.

      └──▷ GET THIS VERSION 
      $ git clone --branch v0.4.0 https://github.com/miek/inspectrum.git
# already have the repo? check out this version:
$ git checkout v0.4.0
      • Supports Qt 6, enabling builds against the current Qt toolkit.
      • Adds support for opening SigMF datasets, allowing analysis of signals stored in the standardized SigMF format.

      2 details in Everything

      └──▷ BREAKING ON UPGRADE
      • !CMake minimum version requirement raised from 3.1 to 3.5; builds using CMake older than 3.5 will fail.
    2. v0.2.3 Dec 4, 2020 · release notes

      inspectrum v0.2.3 adds support for files with real-valued samples

      └──▷ GET THIS VERSION 
      $ git clone --branch v0.2.3 https://github.com/miek/inspectrum.git
# already have the repo? check out this version:
$ git checkout v0.2.3
    3. v0.2 Feb 3, 2017 · release notes

      inspectrum v0.2 adds cursor-based symbol extraction and new trace plots

      └──▷ GET THIS VERSION 
      $ git clone --branch v0.2 https://github.com/miek/inspectrum.git
# already have the repo? check out this version:
$ git checkout v0.2
      └──▷ HOW TO FIND IT
      Extract specific symbol boundaries from a captured trace by placing markers.
      📍Use the cursor tool to place two markers on the plot, then trigger 'symbol extraction using cursor positions'
      Export the visualized signal data for external analysis or documentation.
      📍Use the data export option from the view menu to save the current plot state
      • Adds cursors for placing markers on the time-domain plot
      • Enables symbol extraction using cursor positions to identify signal boundaries
      • Introduces additional plot types for IQ samples, amplitude, frequency, and phase data
      • Allows data export of the current view
      • Adds support for sc8, uc8, and sc16 file formats

      5 details in Everything

    Project health

    Issue, contributor and maintainer activity in miek/inspectrum, 2023-10 – 2026-09, as of 2026-09-25. Twelve-month figures first; the trend lines run the whole window.

    1. Contributors 1 ±0 vs prior 12 months
    2. Maintainers 1 +1 joined · −0 left, last 12 months
    3. Bus factor 1 committers behind half the commits
    4. Community-filed 100% of issues opened, last 12 months
    5. Median time to close 149 days issues closed, last 12 months
    6. Open backlog 45 of 143 issues ever filed
    1. Issues opened / month 0 · 0 communitymaintainers
    2. Open backlog 45
    3. Contributors / month 0
    4. Commits / month 0
    5. Stars 2,512
    Issue themes, last 12 months
    • other 100%

    Counts from the project's public repository and git history; no individuals are identified. Maintainers are the committers covering 80% of the last year's commits. how we measure this

    Libraries its release ships

    What its latest release locks, checked against known advisories.

    None of its release's images build from a lockfile we can read.

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