// SPECTER SDR HELP

Radiation Counter and Timeline

Connect a supported GQ GMC counter, view its own trace, and compare radiation readings with RF session timing.

Reviewed September 24, 2026 against source v1.7.41. Features and fixes are labeled by version. Check release availability.

A separate instrument, not a radio channel

SPECTER SDR can read compatible GQ GMC counters through their USB serial protocol. The radiation trace is separate from the SDR cards and tinySA spectrum sweeps. A counter does not provide RF spectrum, demodulated audio, IQ samples, or protocol decoding.

Connect and enable

  1. Connect the powered counter with a USB data cable and close other software that owns its serial port.
  2. Open Settings > System, enable Geiger counter (GQ GMC), and save.
  3. Wait for identification and a live counts-per-minute readout. If it does not appear, use Check USB Connection and inspect the sidecar log.

Do not replace the counter's serial driver with the RTL-SDR WinUSB driver. Follow the counter manufacturer's driver and calibration guidance. Protocol compatibility does not imply that every GQ model has been physically validated.

Read the strip

In v1.7.40 the Geiger trace has its own row above the receivers, so adding radios no longer squeezes it. In v1.7.41, the workspace places radios first, spectrum analyzers below them, and the radiation strip at the bottom. A counter that disconnects after being seen remains visible as disconnected. See version availability.

Background-based alerts and recordings

The app compares readings with a learned local background rather than a single fixed CPM threshold. The default excursion sensitivity is four sigma. Radiation alerts controls notifications; turning it off does not turn off the live trace or radiation telemetry in an active session recording.

Start a session recording to retain counter readings on the same timeline as RF observations. A time coincidence is something to review, not proof that one measurement caused another.

Use the counter's calibration, manufacturer instructions, and appropriate radiation-safety procedures for safety decisions. SPECTER's background comparison is an analysis aid, not a calibrated dose assessment or a safety clearance.

If the trace stops

Check power, the data cable, the port in use, and whether another application has opened it. A disconnected label is not a zero-radiation reading. Include the exact counter model and relevant sidecar log lines in a private support ticket.