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trx-rs/docs/User-Manual.md
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sjgandClaude Opus 5 cfaeb6ee15 [docs](trx-rs): generate the example config and correct the manual 
trx-rs.toml.example was maintained by hand and had fallen well behind: no
[[rigs]], no [[remotes]], no [timeouts], no bandplan or decode-history
settings, and a [frontends.http].default_rig_id that had been renamed.

Generate it from the config structs instead, so a new field shows up the moment
it exists, and add a test that fails when the checked-in copy drifts:

    cargo run -p trx-config --example generate_example

Section comments come from a small table; a section without an entry is still
emitted, so forgetting a comment can never drop a setting from the example.

The manual was wrong about the basics.  It listed five config search paths, none
of which the loader has ever looked at (the real order is ./trx-rs.toml → XDG →
/etc), called --print-config output "fully commented" when it carries no
comments at all, and documented a TRX_PLUGIN_DIRS variable no code reads.  It
also still described [frontends.rigctl].port as the bind port years after
rig_ports replaced it.  Fixed, and the new configuration features are written
up alongside.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SyX26FCpMQxiBoC7r5K1A7
Signed-off-by: Stan Grams <sjg@haxx.space>
2026-08-06 21:32:46 +02:00

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# trx-rs Manual
## What trx-rs is
`trx-rs` is a modular amateur radio control stack written in Rust. It splits
hardware access, DSP, transport, and user-facing interfaces into separate
components so a radio or SDR can be controlled locally while audio, decoding,
and remote control are exposed elsewhere on the network.
In practice, `trx-server` owns the rig or SDR backend and runs the DSP
pipeline, while `trx-client` connects to it and provides frontends such as the
web UI, JSON control, and rigctl-compatible access. The workspace also includes
protocol decoders and plugin-based extension points for adding backends and
frontends.
---
## Configuration
Both `trx-server` and `trx-client` read TOML. The server takes its settings
from the `[trx-server]` section and the client from `[trx-client]`, so one
`trx-rs.toml` can configure both — or each may live in its own file with the
section header left off.
`trx-rs.toml.example` in the repository root is a complete, commented example
generated from the config definitions themselves. `--print-config` prints the
same settings without the comments.
### File Locations
Both binaries use the same lookup order:
1. `--config <FILE>`
2. `./trx-rs.toml`
3. `~/.config/trx-rs/trx-rs.toml`
4. `/etc/trx-rs/trx-rs.toml`
CLI arguments override config file values.
### Checking a Config
`--check-config` loads the file, reports every problem it finds — unknown keys,
invalid values, listeners fighting over a port — and exits without starting
anything:
```bash
trx-server --check-config --config trx-rs.toml
trx-client --check-config --config trx-rs.toml
```
Unknown keys are warnings by default, so a config written for a newer version
still runs on an older binary. `--strict-config` makes them fatal.
`trx-configurator --check <FILE>` runs the same checks.
### Environment Variables and Secrets
Any string in the config may reference an environment variable as `${VAR}`;
an unset variable is an error rather than an empty value.
Credentials can be kept out of the config entirely by pointing at a file
instead. Every secret has a `*_file` sibling — set one or the other, never
both:
| Inline key | File key | Contents |
|------------|----------|----------|
| `[listen.auth].tokens` | `tokens_file` | one token per line |
| `[[remotes]].auth.token` | `token_file` | the token |
| `[frontends.http.auth].rx_passphrase` | `rx_passphrase_file` | the passphrase |
| `[frontends.http.auth].control_passphrase` | `control_passphrase_file` | the passphrase |
| `[frontends.http_json.auth].tokens` | `tokens_file` | one token per line |
Blank lines and `#` comments are ignored in the list files. A config that holds
credentials inline and is readable by group or others is flagged at startup.
### Server Options
#### `[general]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `callsign` | string | `"N0CALL"` | Station callsign |
| `log_level` | string | — | `trace`, `debug`, `info`, `warn`, or `error` |
| `latitude` | float | — | Station latitude (-90..90) |
| `longitude` | float | — | Station longitude (-180..180) |
`latitude` and `longitude` must be set together or both omitted.
#### `[rig]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `model` | string | — | Backend name (`ft817`, `ft450d`, `soapysdr`) |
| `initial_freq_hz` | u64 | `144300000` | Startup frequency (must be > 0) |
| `initial_mode` | string | `"USB"` | Startup mode |
#### `[rig.access]`
| Field | Type | Description |
|-------|------|-------------|
| `type` | string | `serial`, `tcp`, or `sdr` |
| `port` | string | Serial port path (serial mode) |
| `baud` | u32 | Serial baud rate (serial mode) |
| `host` | string | Remote host (tcp mode) |
| `tcp_port` | u16 | Remote port (tcp mode) |
| `args` | string | SoapySDR device args (sdr mode, e.g. `"driver=rtlsdr"`) |
#### `[behavior]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `poll_interval_ms` | u64 | `500` | Rig polling interval |
| `poll_interval_tx_ms` | u64 | `100` | Polling interval during TX |
| `max_retries` | u32 | `3` | Connection retry limit |
| `retry_base_delay_ms` | u64 | `100` | Base retry delay |
#### `[listen]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `enabled` | bool | `true` | Enable JSON TCP listener |
| `listen` | ip | `127.0.0.1` | Bind address |
| `port` | u16 | `4530` | Bind port |
#### `[listen.auth]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `tokens` | string[] | `[]` | Allowed auth tokens (empty = no auth) |
| `tokens_file` | string | — | Read tokens from this file, one per line |
#### `[audio]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `enabled` | bool | `true` | Enable audio streaming |
| `listen` | ip | `127.0.0.1` | Bind address |
| `port` | u16 | `4531` | Bind port |
| `rx_enabled` | bool | `true` | Enable RX audio |
| `tx_enabled` | bool | `true` | Enable TX audio |
| `device` | string | — | CPAL device name (empty = default) |
| `sample_rate` | u32 | `48000` | Sample rate (8000–192000) |
| `channels` | u8 | `1` | Channel count (1 or 2) |
| `frame_duration_ms` | u16 | `20` | Opus frame duration (3, 5, 10, 20, 40, 60) |
| `bitrate_bps` | u32 | `24000` | Opus bitrate |
When audio is enabled, at least one of `rx_enabled` or `tx_enabled` must be true.
#### `[sdr]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `sample_rate` | u32 | `1920000` | IQ capture rate in Hz |
| `bandwidth` | u32 | `1500000` | Hardware IF filter bandwidth in Hz |
| `center_offset_hz` | i64 | `100000` | Offset from dial to avoid DC spur |
#### `[sdr.gain]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `mode` | string | `"auto"` | `"auto"` (hardware AGC) or `"manual"` |
| `value` | f64 | `30.0` | Gain in dB (manual mode only) |
#### `[sdr.squelch]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `enabled` | bool | `false` | Enable software squelch |
| `threshold_db` | f32 | `-65.0` | Open threshold in dBFS (-140..0) |
| `hysteresis_db` | f32 | `3.0` | Close hysteresis in dB (0..40) |
| `tail_ms` | u32 | `180` | Tail hold time in ms (0..10000) |
#### `[[sdr.channels]]`
Defines virtual receiver channels within the wideband IQ stream. The first
channel is the primary channel (controlled by `set_freq`/`set_mode`).
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `id` | string | `""` | Human-readable label |
| `offset_hz` | i64 | `0` | Frequency offset from dial |
| `mode` | string | `"auto"` | Demod mode (`auto`, `LSB`, `USB`, `CW`, `AM`, `FM`, `WFM`, etc.) |
| `audio_bandwidth_hz` | u32 | `3000` | Post-demod audio bandwidth |
| `fir_taps` | usize | `64` | FIR filter tap count |
| `cw_center_hz` | u32 | `700` | CW tone centre frequency |
| `wfm_bandwidth_hz` | u32 | `75000` | WFM pre-demod filter bandwidth |
| `decoders` | string[] | `[]` | Decoder IDs for this channel (`ft8`, `wspr`, `aprs`, `cw`) |
| `stream_opus` | bool | `false` | Stream this channel's audio to clients |
Notes:
- Each decoder ID may appear in at most one channel.
- At most one channel may set `stream_opus = true`.
- Channel IF constraint: `|center_offset_hz + offset_hz| < sample_rate / 2`.
#### `[pskreporter]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `enabled` | bool | `false` | Enable PSKReporter uplink |
| `host` | string | `"report.pskreporter.info"` | Server host |
| `port` | u16 | `4739` | Server port |
| `receiver_locator` | string | — | Maidenhead grid (derived from lat/lon if omitted) |
#### `[aprsfi]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `enabled` | bool | `false` | Enable APRS-IS IGate |
| `host` | string | `"rotate.aprs.net"` | Server host |
| `port` | u16 | `14580` | Server port |
| `passcode` | i32 | `-1` | APRS-IS passcode (-1 = auto from callsign) |
Notes:
- `[general].callsign` must be non-empty when enabled.
- Only APRS packets with valid CRC are forwarded.
- Reconnects with exponential backoff (1 s → 60 s) on TCP errors.
#### `[decode_logs]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `enabled` | bool | `false` | Enable decoder logging |
| `dir` | string | `"$XDG_DATA_HOME/trx-rs/decoders"` | Log directory |
| `aprs_file` | string | `"TRXRS-APRS-%YYYY%-%MM%-%DD%.log"` | APRS log filename |
| `cw_file` | string | `"TRXRS-CW-%YYYY%-%MM%-%DD%.log"` | CW log filename |
| `ft8_file` | string | `"TRXRS-FT8-%YYYY%-%MM%-%DD%.log"` | FT8 log filename |
| `wspr_file` | string | `"TRXRS-WSPR-%YYYY%-%MM%-%DD%.log"` | WSPR log filename |
Files are appended in JSON Lines format. Supported date tokens: `%YYYY%`,
`%MM%`, `%DD%` (UTC).
#### `[decoders]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `enabled` | string[] | all decoders | Decoders to run for this rig |
| `output_dir` | string | `"$XDG_CACHE_HOME/trx-rs"` | Base directory for decoders that write images |
Valid decoder names: `aprs`, `aprs_hf`, `ais`, `cw`, `ft2`, `ft4`, `ft8`,
`lrpt`, `sstv`, `vdes`, `wefax`, `wspr` — the same names `[[sdr.channels]]`
uses. An unrecognised name is a config error.
Every decoder runs by default, which costs real CPU on a small machine. On a
station that only works digital modes, listing just what you use is worth it:
```toml
[decoders]
enabled = ["ft8", "ft4", "wspr"]
```
`sstv`, `wefax` and `lrpt` write images into a subdirectory of `output_dir`
named after the decoder. `ais` and `vdes` additionally require an SDR channel
configured to feed them.
#### Multi-Rig Configuration
Use `[[rigs]]` arrays instead of the flat `[rig]` section for multi-rig setups:
```toml
[[rigs]]
id = "ft817_0"
name = "HF Transceiver"
[rigs.rig]
model = "ft817"
[rigs.rig.access]
type = "serial"
path = "/dev/ttyUSB0"
baud = 9600
[[rigs]]
id = "sdr_0"
name = "VHF/UHF SDR"
[rigs.rig]
model = "soapysdr"
[rigs.rig.access]
type = "sdr"
args = "driver=rtlsdr"
```
When `[[rigs]]` is present it takes priority over the flat `[rig]` section.
Rigs without an explicit `id` get auto-generated IDs like `ft817_0`, `soapysdr_1`.
### Client Options
#### `[general]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `callsign` | string | `"N0CALL"` | Station callsign |
| `log_level` | string | — | `trace`, `debug`, `info`, `warn`, or `error` |
#### `[remote]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `url` | string | — | Server address (e.g. `localhost:4530`) |
| `poll_interval_ms` | u64 | `750` | State poll interval |
#### `[remote.auth]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `token` | string | — | Auth token (must not be empty if set) |
| `token_file` | string | — | Read the token from this file instead |
#### `[[remotes]]`
Preferred over the single `[remote]` section: one entry per rig, each mapping a
short name to a server and an optional server-side rig id.
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `name` | string | — | Short name used everywhere in the client |
| `url` | string | — | Server address (`host:port`) |
| `rig_id` | string | — | Rig id on a multi-rig server |
| `auth.token` | string | — | Auth token |
| `auth.token_file` | string | — | Read the token from this file instead |
| `poll_interval_ms` | u64 | `750` | State poll interval |
The `name` is the key used by `default_rig_name`, `rigctl.rig_ports`,
`audio.rig_urls`, `audio.rig_ports` and `decode_history_retention_min_by_rig`.
A name in any of those maps that no remote answers to is a config error.
#### `[frontends.http]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `enabled` | bool | `true` | Enable web UI |
| `listen` | ip | `127.0.0.1` | Bind address |
| `port` | u16 | `8080` | Bind port |
| `default_rig_name` | string | — | Remote selected on startup |
| `initial_map_zoom` | u8 | `10` | Starting zoom for the APRS map |
| `show_sdr_gain_control` | bool | `true` | Expose the RF gain control |
| `bandplan_enabled` | bool | `true` | Show the bandplan strip |
| `bandplan_region` | string | `"iaru_r1"` | `iaru_r1`, `iaru_r2`, or `iaru_r3` |
| `decode_history_retention_min` | u64 | `1440` | Decode history retention |
| `decode_history_retention_min_by_rig` | table | `{}` | Per-remote retention override |
| `spectrum_coverage_margin_hz` | u32 | `50000` | Centre-retune guard margin |
| `spectrum_usable_span_ratio` | f32 | `0.92` | Usable fraction of the sampled span |
#### `[frontends.http.auth]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `enabled` | bool | `false` | Require a passphrase |
| `rx_passphrase` | string | — | Passphrase granting receive-only access |
| `rx_passphrase_file` | string | — | Read it from this file instead |
| `control_passphrase` | string | — | Passphrase granting full control |
| `control_passphrase_file` | string | — | Read it from this file instead |
| `tx_access_control_enabled` | bool | `true` | Hide TX from unauthenticated users |
| `session_ttl_min` | u64 | `480` | Session lifetime |
| `cookie_secure` | bool | `false` | Set Secure on the session cookie (needs HTTPS) |
| `cookie_same_site` | string | `"Lax"` | `Strict`, `Lax`, or `None` |
With `enabled = true`, at least one passphrase must be set.
#### `[frontends.rigctl]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `enabled` | bool | `false` | Enable Hamlib rigctl |
| `listen` | ip | `127.0.0.1` | Bind address |
| `rig_ports` | table | `{}` | Remote name → local port; one listener each |
One listener is started per `rig_ports` entry, each routing to its rig, so
`rig_ports` must name at least one remote when the frontend is enabled. The
older single `port` key and `--rigctl-port` are ignored.
#### `[frontends.http_json]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `enabled` | bool | `true` | Enable JSON-over-TCP |
| `listen` | ip | `127.0.0.1` | Bind address |
| `port` | u16 | `0` | Bind port (0 = ephemeral) |
| `auth.tokens` | string[] | `[]` | Allowed auth tokens |
| `auth.tokens_file` | string | — | Read tokens from this file, one per line |
#### `[frontends.audio]`
| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `enabled` | bool | `true` | Enable audio client |
| `server_url` | string | — | Audio endpoint for every remote |
| `rig_urls` | table | `{}` | Remote name → audio URL (wins over `server_url`) |
| `server_port` | u16 | `4531` | Fallback port when no URL is configured |
| `rig_ports` | table | `{}` | Remote name → port; superseded by `rig_urls` |
| `bridge.enabled` | bool | `false` | Enable local CPAL audio bridge |
| `bridge.rx_output_device` | string | — | Local playback device |
| `bridge.tx_input_device` | string | — | Local capture device |
| `bridge.rx_gain` | float | `1.0` | RX playback gain |
| `bridge.tx_gain` | float | `1.0` | TX capture gain |
The bridge is intended for WSJT-X integration via virtual audio devices (ALSA
loopback on Linux, BlackHole on macOS).
### CLI Override Summary
**trx-server:**
`--config`, `--print-config`, `--check-config`, `--strict-config`, `--rig`,
`--access`, `--callsign`, `--listen`, `--port`. SDR options are file-only.
**trx-client:**
`--config`, `--print-config`, `--check-config`, `--strict-config`, `--url`,
`--token`, `--poll-interval`, `--rig-id`, `--frontend`, `--http-listen`,
`--http-port`, `--rigctl-listen`, `--http-json-listen`, `--http-json-port`,
`--callsign`.
`--listen` on the server overrides the bind address of both the control
listener and every rig's audio listener.
---
## Tune Links
Every page of the web UI carries what the radio is doing in its address, so the
URL in the address bar is always a link someone else can open:
```
http://receiver.example:8080/?rig=sdr&f=14074000&mode=USB&bw=3000
```
| Parameter | Meaning |
|-----------|---------|
| `f` | Frequency. Hz by default; `7074k` and `14.074M` also work. |
| `mode` | Demodulation mode, e.g. `USB`, `CW`, `WFM`. |
| `bw` | Filter bandwidth in Hz. Ignored by rigs without filter control. |
| `rig` | Rig to select first, by id, on a multi-rig client. |
Opening such a link selects the rig, sets the mode, tunes, and applies the
bandwidth, in that order — a mode change carries its own default bandwidth, so
an explicit `bw` is applied last. Anything the rig cannot do (an unknown mode,
a frequency outside its range) is reported and the rest of the link still
applies. All four parameters are optional.
The link button in the top bar copies the current link to the clipboard. The
address bar itself is updated as you tune, using `replaceState`, so sweeping
the dial does not fill the browser's history.
Applying a link changes the radio, so it needs the `control` role; an `rx`
session opens the page and says the link was not applied. Links describe the
rig's own dial — while a tab is listening to a virtual channel the address is
left as it was, rather than publishing a frequency the rig is not on.
---
## Authentication
The HTTP frontend supports optional passphrase-based authentication with two
roles:
- **rx** — read-only access (monitoring, audio, decode streams)
- **control** — full access (frequency, mode, PTT, and all settings)
### Configuration
```toml
[frontends.http.auth]
enabled = false
rx_passphrase = "rx-only-passphrase"
control_passphrase = "full-control-passphrase"
tx_access_control_enabled = true
session_ttl_min = 480
cookie_secure = false # true if served via HTTPS
cookie_same_site = "Lax" # Strict|Lax|None
```
When `enabled = false` (the default), all auth is bypassed and the UI behaves
as before. When enabled, at least one passphrase must be set.
### Behaviour
- On login, the server issues an `HttpOnly` session cookie.
- Sessions are in-memory; a server restart invalidates all sessions.
- Rate limiting is applied per IP to mitigate brute-force attempts.
- When `tx_access_control_enabled = true`, TX/PTT controls are hidden and
rejected for unauthenticated or `rx`-role users.
### Routes
| Endpoint | Method | Description |
|----------|--------|-------------|
| `/auth/login` | POST | Submit `{ "passphrase": "..." }` |
| `/auth/logout` | POST | Clear session |
| `/auth/session` | GET | Check current session/role |
Protected routes require at least `rx` role. Control routes (set frequency,
mode, PTT, etc.) require `control` role.
### Frontend Flow
1. On load, the UI calls `/auth/session`.
2. If unauthenticated, a login screen is shown.
3. On successful login, the normal UI loads.
4. `rx` users see a read-only interface; `control` users get full controls.
5. If a session expires mid-use, streams stop and the login screen returns.
### Transport Security
There is no built-in TLS. For remote access, place trx-rs behind a
TLS-terminating reverse proxy (nginx, Caddy) and set `cookie_secure = true`.
---
## Background Decoding Scheduler
The scheduler automatically retunes the rig to pre-configured bookmarks when no
users are connected to the HTTP frontend. It runs as a background task inside
`trx-frontend-http`, polling every 30 seconds.
### Modes
#### Disabled (default)
Scheduler is inactive. The rig is not touched automatically.
#### Grayline
Retunes around the solar terminator (day/night boundary).
The user provides:
- Station latitude and longitude (decimal degrees)
- Optional transition window width (minutes, default 20)
- Bookmark IDs for four periods:
- **Dawn** — window around sunrise (`sunrise ± window_min/2`)
- **Day** — after dawn until dusk
- **Dusk** — window around sunset (`sunset ± window_min/2`)
- **Night** — after dusk until next dawn
Period precedence (most specific wins): Dawn > Dusk > Day > Night.
If no bookmark is assigned to a period, the rig is not retuned for that period.
Sunrise/sunset is computed inline using the NOAA simplified algorithm. Polar
regions (midnight sun / polar night) fall back to Day/Night accordingly.
#### TimeSpan
Retunes according to a list of user-defined time windows (UTC).
Each entry specifies:
- `start_hhmm` — start of window (e.g. 600 = 06:00 UTC)
- `end_hhmm` — end of window (e.g. 700 = 07:00 UTC)
- `bookmark_id` — bookmark to apply
- `label` — optional human-readable description
Windows that span midnight (`end_hhmm < start_hhmm`) are supported. When
multiple entries overlap, the first match (by list order) wins.
### Storage
Configuration is stored in PickleDB at `~/.config/trx-rs/scheduler.db`.
Keys: `sch:{rig_id}` → JSON `SchedulerConfig`.
### HTTP API
All read endpoints are accessible at the **Rx** role level. Write endpoints
require the **Control** role.
| Method | Path | Description |
|--------|------|-------------|
| GET | `/scheduler/{rig_id}` | Get scheduler config for a rig |
| PUT | `/scheduler/{rig_id}` | Save scheduler config (Control only) |
| DELETE | `/scheduler/{rig_id}` | Reset config to Disabled (Control only) |
| GET | `/scheduler/{rig_id}/status` | Get last-applied bookmark and next event |
### Activation Logic
Every 30 seconds the scheduler task checks:
1. No SSE clients connected
2. Active rig has a non-Disabled scheduler config
3. Current UTC time matches a scheduled window or grayline period
4. If the matching bookmark differs from last applied, send `SetFreq` + `SetMode`
The scheduler does not revert changes when users reconnect.
### Web UI
A dedicated tab with a clock icon provides:
- Rig selector (read-only, shows active rig)
- Mode picker: Disabled / Grayline / TimeSpan
- Grayline section: lat/lon inputs, transition window slider, four bookmark selectors
- TimeSpan section: table of entries with start/end times, bookmark, label
- Status card: last applied bookmark name and timestamp
- Save button (Control role only)
---
## SDR Noise Blanker
The noise blanker suppresses impulse noise (clicks, pops, ignition interference)
on raw IQ samples before any mixing or filtering takes place. It works by
tracking a running RMS level of the signal and replacing any sample whose
magnitude exceeds **threshold x RMS** with the last known clean sample.
### Configuration (server-side)
The noise blanker is configured per rig. In a multi-rig setup each
`[[rigs]]` entry has its own `[rigs.sdr.noise_blanker]` section:
```toml
[[rigs]]
id = "hf"
[rigs.rig]
type = "sdr"
[rigs.sdr.noise_blanker]
enabled = true
threshold = 10.0 # 1 – 100; lower = more aggressive blanking
```
For the legacy single-rig (flat) config the path is `[sdr.noise_blanker]`:
```toml
[sdr.noise_blanker]
enabled = true
threshold = 10.0
```
| Field | Type | Default | Range | Description |
|-------------|-------|---------|---------|-------------|
| `enabled` | bool | false | — | Turn the noise blanker on or off. |
| `threshold` | float | 10.0 | 1 – 100 | Multiplier applied to the running RMS. A sample whose magnitude exceeds this multiple is replaced. Lower values blank more aggressively; higher values only catch strong impulses. |
The noise blanker is off by default.
### Choosing a threshold
The threshold controls how aggressively the blanker suppresses impulses.
A value of **N** means: blank any sample whose magnitude exceeds **N times**
the running average signal level.
| Threshold | Behavior | Use case |
|-----------|----------|----------|
| 3 – 5 | Very aggressive — blanks frequently | Dense impulse noise (motors, power lines, LED drivers nearby) |
| 8 – 12 | Moderate — catches clear spikes without touching normal signals | Typical HF conditions with occasional ignition or switching noise |
| 15 – 25 | Conservative — only blanks strong impulses well above the noise floor | Light interference, or when you want minimal artifacts on weak signals |
| 30 – 100 | Very light — rarely triggers | Faint, infrequent clicks; mostly a safety net |
**Start at 10** (the default) and adjust while listening:
- If impulse noise is still audible, lower the threshold.
- If weak signals sound choppy or distorted, raise it — the blanker may be
mistaking signal peaks for noise.
- On bands with steady atmospheric noise (e.g. 160 m / 80 m), a threshold of
**5 – 8** usually works well.
- On quieter VHF/UHF bands where the noise floor is low, values of **15 – 25**
avoid false triggers from strong signals.
### Web UI
When the server reports noise-blanker support, two controls appear in the
**SDR Settings** row of the web interface:
- **Noise Blanker** checkbox — enables or disables the blanker in real time.
- **NB Threshold** number input (1–100) with a **Set** button — adjusts the
detection threshold. Press Enter or click Set to apply.
Both controls stay hidden until the server sends filter state containing NB
fields, so they only appear when connected to an SDR backend.
### HTTP API
```
POST /set_sdr_noise_blanker?enabled=true&threshold=10
```
| Parameter | Type | Required | Description |
|-------------|--------|----------|-------------|
| `enabled` | bool | yes | `true` or `false` |
| `threshold` | float | yes | Value between 1 and 100 |
### How it works
The blanker runs on every IQ block (4096 samples) *before* the mixer stage in
the DSP pipeline:
1. For each sample, compute magnitude² (`re² + im²`).
2. Compare against `threshold² × mean_sq` (the exponentially-smoothed running
mean of magnitude²).
3. If the sample exceeds the threshold, replace it with the previous clean
sample.
4. Otherwise, update the running mean with smoothing factor α = 1/128 and store
the sample as the last clean value.
Because the blanker operates on raw IQ before frequency translation, it removes
impulse noise across the entire captured bandwidth regardless of the tuned
channel offset.
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