trx-rs/docs/User-Manual.md

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.

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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:

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
spectrum_fft_size	usize	1024	Spectrum FFT bins; power of two, 128–8192
spectrum_interval_ms	u64	50	How often a spectrum frame is pushed to subscribed clients

Spectrum is the largest thing on the client connection. On a slow or high-latency link, halving spectrum_fft_size halves the bytes per frame (at half the frequency resolution) and raising spectrum_interval_ms sends fewer of them; see Spectrum over a slow link.

[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:

[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:

[[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
spectrum_interval_ms	u64	50	Spectrum frame interval; also settable per [[remotes]] entry

[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).

Spectrum over a slow link

Spectrum dominates the server↔client connection: everything else is a few hundred bytes, a frame is a few kilobytes. Three things govern what it costs.

Frames are pushed, not polled. The client subscribes and the server sends frames at [sdr].spectrum_interval_ms. Polling cost a round trip per frame, so the rate was capped at 1/RTT — on a 200 ms link you could not exceed 5 frames a second however often the client asked. Clients fall back to polling automatically against a server too old to stream.

Bins travel as whole dBFS. They are base64-encoded i8 on the wire, about an eighth of the JSON array of floats they used to be, at the resolution the display draws anyway.

Both ends have a rate, and the slower one wins. The server pushes no faster than [sdr].spectrum_interval_ms; the client asks for no more than [[remotes]].spectrum_interval_ms.

For a link that struggles, start here:

[trx-server.sdr]
spectrum_fft_size = 512      # half the bins, half the bytes
spectrum_interval_ms = 200   # 5 frames/s instead of 20

[[trx-client.remotes]]
name = "remote-site"
url = "radio.example.com:4530"
spectrum_interval_ms = 200

That is roughly 0.7 KB per frame at 5 frames/s — about 3.5 KB/s, against roughly 200 KB/s for 1024 float bins at 20 frames/s.

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.

---

Multiple Rigs in the Web UI

A client connected to several rigs decodes all of them at once, whichever one is on screen. The rig picker in the header decides which rig the UI is about, and each page answers that differently:

Page	Shows
Radio	The selected rig: its spectrum, its audio, and the mini decode views over the waterfall.
Digital Modes	The selected rig: every decoder panel, its counts and its status line.
Map	The whole station — every rig's positions, with the map's own rig filter to narrow it. HF APRS is a source of its own there, filtered apart from VHF APRS.
Statistics	The whole station, including the per-rig comparison.

Switching rigs repaints the radio and digital modes pages for the rig now selected. Nothing is lost by switching: the traffic other rigs heard is still held, and switching back brings it up again. The one exception is the CW pane, which is a single running stream of copied text rather than a list of frames, so it starts empty on the rig you switch to.

Each browser tab keeps its own selection, so two tabs can watch two rigs.

---

Logbook

The Logbook tab keeps the station's contacts and speaks ADIF, so a log can be uploaded to LoTW, eQSL, Club Log or QRZ, or moved to another logger.

An entry opens pre-filled with six fields and no more: the frequency, mode and name of the rig you are on, the time from the server's clock, and — when the entry was started from a decode or a map station — that station's callsign and locator. Signal reports, name, comment and the rest are yours to fill in; a report in particular is never guessed, because an FT8 SNR is not what was sent.

Your own callsign and locator are not per-contact fields. They are station identity: the callsign comes from [trx-client.general].callsign, the locator from the rig's position, and both are shown once at the top of the panel. The operator defaults to the station callsign and can be changed for the session, which is what a multi-operator station needs.

Times are the server's, in UTC — the server is the machine at the radio. If the browser's clock disagrees by more than a second the entry says so rather than logging a time you did not expect.

A decode is not a contact. The decoders are receive-only, so a Log button on an FT8 or APRS row opens an entry with what was heard in it and logs nothing by itself. Digital QSOs made in WSJT-X come in through Import ADIF, the way every other logger takes them.

Action	What it does
Log contact	Writes the entry and opens a fresh one
Export ADIF	Downloads the log — filtered, if a filter is set
Import ADIF	Reads a file, skipping contacts already held and reporting what could not be read
Worked before	Shows, as you type a callsign, which bands and modes it has been worked on

Two contacts are treated as the same when the callsign, band and mode match and the times are within two minutes: two loggers rarely stamp a QSO to the same minute, one recording when it started and the other when it was typed.

The log is a JSON Lines file, appended one contact at a time so a crash costs at most the contact being written. It lives in your data directory by default; [trx-client.logbook].path moves it, for a station that keeps its log on a backed-up volume.

Ham radio layout

The Ham radio operator layout opens on the logbook with the transceiver controls around it — the arrangement for working the bands, where logging the contact is the task and the radio is the instrument. It is offered only where the selected rig can transmit; a receiver has no contacts to log.

---

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

[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:

[[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]:

[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.