Substation configuration: scanner
The 5 settings under scanner, each with the type, default and limits its schema declares.
Scanner settings, applying to every band.
These settings control how the scanner reads IQ samples from the SDR, how it buffers them, and whether it calibrates the receiver's frequency at startup.
sdr_device_sample_size in scanner
- Type
integer- Default
131072- Limits
- above 0
Size, in IQ samples, of the blocks each slice is built from. The scanner rounds every slice up to a whole number of these blocks, so this also sets the shortest possible slice. On an RTL-SDR it must be a multiple of 256, for example 65536.
band_time_slice_ms in scanner
- Type
integer- Default
200- Limits
- above 0
How often the scanner analyses the spectrum, in milliseconds. The scanner
reads, queues, and processes IQ samples one slice at a time, and rounds each
slice up to a whole number of sdr_device_sample_size blocks, so at low
sample rates a slice can be longer than this. Shorter slices detect brief
transmissions sooner; longer slices use less CPU and more memory.
sample_queue_maxsize in scanner
- Type
integer- Default
200- Limits
- above 0
Number of slices of IQ samples the scanner holds while processing catches up. When the queue is full, the scanner drops newly arriving slices with a warning and keeps the slices already queued. A larger queue tolerates longer processing spikes, such as several radio channels activating at once. Each queued slice holds every IQ sample in it, so at high sample rates a full queue can need more memory than a small computer has: lower it there.
calibration_frequency_hz in scanner
- Type
numberornull- Default
null- Limits
- above 0
Frequency in Hz of a strong, steady local signal that the scanner uses at startup to measure and correct the receiver's frequency error. Null, the default, leaves the receiver's correction as it is. An FM broadcast station is the usual choice, because it is on air all day at a fixed frequency: in parts of the UK, 93.7e+6 is BBC Radio 4. Pick a station you receive well, since the scanner skips calibration with a warning, and leaves the correction unchanged, when it finds no strong, steady signal there. Only RTL-SDR receivers have a PPM correction control; other devices skip calibration.
stuck_channel_threshold_seconds in scanner
- Type
numberornull- Default
60- Limits
- above 0
Time in seconds after which the scanner warns that a radio channel has stayed active, which usually points to interference or a stuck transmitter. The scanner repeats the warning at most once a minute and keeps detecting and recording. Recommended: 30-120 seconds. Set to null to turn the warning off.