NFM 12.5 kHz Span 2.4 MHz

Center 100.000 000 MHzOffset +0.000 kHz

S1S3S5S7S9+20+40

-- dBFS

SCAN ACTIVITY Scanning…

Freq MHz	What / where	SNR	Heard

SIGINT workbench

Connect an RTL-SDR to measure, classify, survey, direction-find, and keep interference notes. Everything runs in this tab.

Tools

Signal measurement & classification, band occupancy survey, manual direction finding, interference worksheet, intercept log.

Browser

Chrome or Edge 89+, desktop or Android. Firefox and Safari do not implement WebUSB.

Manual tuning

Step

Signal discovery 0 in use

Finds what's transmitting around you, no frequency needed. Press Scan around me to sweep the bands; hits appear below the spectrum while you scan.

Investigate while scanning — stop on each new find

Band filter · all bands

Nothing lit scans every band. Tap bands to narrow the scan to just those; your selection is kept.

Keep sweeping until I stop (revisits catch brief, intermittent signals)

Connect, then press “Scan around me”. Signals in view are detected automatically.

Freq MHz	What / where	SNR	Heard

Scan settings

Custom MHz to ThresholddB Dwellms

Fewer bands = faster revisits = better odds of catching a brief transmission. On a known channel a signal is named (FRS Ch 1…); otherwise it shows band + width. “?” = seen once. Click a row to tune and watch it.

Signal analysis

Enter a frequency to measure it, or turn on Investigate and scan — a find stops the sweep to analyze or skip. Class is a spectral estimate, not a demodulated ID.

Intercept log

Time	Freq	BW	SNR	Note

Analyze a signal, then “Log for review”. Click a frequency to retune. Stored in this browser only; recording or publishing third-party comms can be unlawful.

Beam-peak log

Beam peak—

Antenna Heading ref

Rotate a directional antenna and log the level at each heading. The dots show where it peaked.

This is a beam-peak record, not a direction fix. One antenna and an uncalibrated RTL power reading cannot resolve a true bearing; sidelobes, multipath, and reflections routinely point the peak the wrong way. Note the antenna type and whether headings are true or magnetic.

Frequency calibration

RTL dongles have a crystal error, so signals sit a few kHz off and narrow channels miss. Tune a known-exact signal (NOAA weather is ideal), then calibrate.

Measured peak—

True MHz

Current correction0 ppm

Quick set: one-shot from the measured peak vs. True MHz. Fine-tune: averages a carrier you hold on True MHz (a keyed handheld, a known station) for a precise correction. Auto: FM 19 kHz pilot, then a local weather carrier cross-check. All apply to every radio and are remembered.

Interference worksheet

A personal note-to-self to organize what you heard. It is not an FCC or military form and files nothing. To report interference, use the FCC complaint portal.

What it looks like Affected system / net Your location

Freq MHz Bandwidth Strength Antenna heading

Char. Impact Duration Remarks

Receiver controls

Bandwidth12.5 kHz

Gain29.7 dB

Squelch

Open

Volume

Tuner AGCRTL

Bias-TOffset

Direct samp. Sample rate Correctionppm FFT size

Reference0 dB

Range80 dB

Averaging0.50

Zoom Palette

Peak hold