# trx-rs Manual

## 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)

Add a `[sdr.noise_blanker]` section to your `trx-server.toml`:

```toml
[sdr.noise_blanker]
enabled = true
threshold = 10.0     # 1 – 100; lower = more aggressive blanking
```

| 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.  A threshold of **10** is a good starting
point for typical HF impulse noise.  Reduce toward **3–5** for heavy QRM;
increase toward **20–30** if weak signals are being clipped.

### 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.