Radio Tuner for WaveCap-SDR

This skill provides tools to adjust SDR radio settings including frequency, gain, squelch, bandwidth, filters, and AGC parameters.

When to Use This Skill

Use this skill when:

Changing the tuned frequency
Adjusting gain for optimal signal level
Setting squelch threshold to eliminate noise
Configuring channel bandwidth
Enabling/disabling filters (deemphasis, notch, etc.)
Adjusting AGC parameters
Changing demodulation mode

Available Settings

Capture Settings (SDR-level)

| Setting | Description | Range | |---------|-------------|-------| | centerHz | Center frequency | 1 MHz - 6 GHz | | sampleRate | Sample rate | Device-dependent | | gain | RF gain | -100 to 100 dB | | bandwidth | IF bandwidth | 0 to sample_rate | | ppm | Frequency correction | -1000 to 1000 | | antenna | Antenna port | Device-dependent |

Channel Settings (Demodulator-level)

| Setting | Description | Range | |---------|-------------|-------| | mode | Demodulation mode | wbfm, nbfm, am, ssb, raw, p25, dmr | | offsetHz | Offset from capture center | -50 MHz to +50 MHz | | squelchDb | Squelch threshold | -120 to 0 dB | | audioRate | Output audio rate | 8000 to 192000 Hz |

Filter Settings

| Setting | Description | Default | |---------|-------------|---------| | enableDeemphasis | FM de-emphasis filter | true (WBFM) | | deemphasisTauUs | De-emphasis time constant | 75 µs (US), 50 µs (EU) | | enableAgc | Automatic gain control | true | | agcTargetDb | AGC target level | -20 dB | | agcAttackMs | AGC attack time | 10 ms | | agcReleaseMs | AGC release time | 500 ms | | notchFrequencies | Notch filter frequencies | [] |

Usage Instructions

Step 1: List Current Settings

Get current capture and channel settings:

# Get capture settings
curl http://127.0.0.1:8087/api/v1/captures/c1 | jq

# Get channel settings
curl http://127.0.0.1:8087/api/v1/channels/ch1 | jq

Or use the helper script:

PYTHONPATH=backend backend/.venv/bin/python .claude/skills/radio-tuner/adjust_settings.py \
  --capture c1 --show

Step 2: Adjust Capture Settings

Change frequency:

curl -X PATCH http://127.0.0.1:8087/api/v1/captures/c1 \
  -H "Content-Type: application/json" \
  -d '{"centerHz": 90300000}'

Change gain:

curl -X PATCH http://127.0.0.1:8087/api/v1/captures/c1 \
  -H "Content-Type: application/json" \
  -d '{"gain": 35.0}'

Or use the helper script:

PYTHONPATH=backend backend/.venv/bin/python .claude/skills/radio-tuner/adjust_settings.py \
  --capture c1 \
  --frequency 90.3 \
  --gain 35

Step 3: Adjust Channel Settings

Change squelch:

curl -X PATCH http://127.0.0.1:8087/api/v1/channels/ch1 \
  -H "Content-Type: application/json" \
  -d '{"squelchDb": -50}'

Change mode:

curl -X PATCH http://127.0.0.1:8087/api/v1/channels/ch1 \
  -H "Content-Type: application/json" \
  -d '{"mode": "nbfm"}'

Enable/disable AGC:

curl -X PATCH http://127.0.0.1:8087/api/v1/channels/ch1 \
  -H "Content-Type: application/json" \
  -d '{"enableAgc": true, "agcTargetDb": -20, "agcAttackMs": 10, "agcReleaseMs": 500}'

Step 4: Add Notch Filters

Remove interference at specific frequencies:

curl -X PATCH http://127.0.0.1:8087/api/v1/channels/ch1 \
  -H "Content-Type: application/json" \
  -d '{"notchFrequencies": [1000, 2000, 3000]}'

Helper Script Reference

# Show current settings
python adjust_settings.py --capture c1 --show

# Change frequency (MHz)
python adjust_settings.py --capture c1 --frequency 90.3

# Change gain (dB)
python adjust_settings.py --capture c1 --gain 35

# Change bandwidth (Hz)
python adjust_settings.py --capture c1 --bandwidth 200000

# Change squelch (dB)
python adjust_settings.py --channel ch1 --squelch -50

# Change mode
python adjust_settings.py --channel ch1 --mode nbfm

# Multiple settings at once
python adjust_settings.py --capture c1 --frequency 90.3 --gain 35 --bandwidth 200000

Demodulation Modes

| Mode | Description | Typical Use | |------|-------------|-------------| | wbfm | Wide-band FM (200 kHz) | FM broadcast radio | | nbfm | Narrow-band FM (12.5-25 kHz) | Two-way radio, amateur | | am | Amplitude modulation | Aviation, AM broadcast | | ssb | Single sideband | Amateur radio, marine | | raw | No demodulation | Digital modes, ISM | | p25 | Project 25 digital | Public safety | | dmr | Digital Mobile Radio | Commercial two-way |

Optimal Settings by Application

FM Broadcast Radio

{
  "sampleRate": 1024000,
  "bandwidth": 200000,
  "mode": "wbfm",
  "enableDeemphasis": true,
  "deemphasisTauUs": 75,
  "squelchDb": -60
}

VHF Marine / Aviation

{
  "sampleRate": 2000000,
  "bandwidth": 25000,
  "mode": "nbfm",
  "squelchDb": -50,
  "enableAgc": true
}

Amateur Radio SSB

{
  "mode": "ssb",
  "ssbMode": "usb",
  "enableSsbBandpass": true,
  "ssbBandpassLowHz": 300,
  "ssbBandpassHighHz": 3000,
  "squelchDb": -60
}

Configuration Warnings

WaveCap-SDR automatically detects problematic configurations and displays warnings in the UI. Check configWarnings in capture API responses to see current warnings.

Check Current Warnings

curl -s http://127.0.0.1:8087/api/v1/captures/c1 | jq '.configWarnings'

Warning Types

| Code | Severity | Description | Resolution | |------|----------|-------------|------------| | rtl_unstable_sample_rate | warning | RTL-SDR sample rate <900kHz causes IQ overflows | Use 1.024 MHz, 2.048 MHz, or 2.4 MHz | | bandwidth_exceeds_sample_rate | warning | Bandwidth > sample rate violates Nyquist | Reduce bandwidth or increase sample rate | | bandwidth_near_sample_rate | info | Bandwidth >90% of sample rate causes edge aliasing | Use bandwidth ≤80% of sample rate | | sdrplay_high_sample_rate | info | SDRplay >8 MHz may cause USB issues | Lower sample rate if experiencing dropouts | | zero_gain | info | Gain set to 0 dB | Increase gain if signals are weak |

Best Practices to Avoid Warnings

RTL-SDR Sample Rates: Use 1.024 MHz, 2.048 MHz, or 2.4 MHz

curl -X PATCH http://127.0.0.1:8087/api/v1/captures/c1 \
  -H "Content-Type: application/json" \
  -d '{"sampleRate": 1024000}'

Bandwidth/Sample Rate Ratio: Keep bandwidth ≤80% of sample rate

# For 2 MHz sample rate, use ≤1.6 MHz bandwidth
curl -X PATCH http://127.0.0.1:8087/api/v1/captures/c1 \
  -H "Content-Type: application/json" \
  -d '{"sampleRate": 2000000, "bandwidth": 1600000}'

SDRplay Sample Rates: Stay ≤8 MHz for reliable USB throughput

curl -X PATCH http://127.0.0.1:8087/api/v1/captures/c1 \
  -H "Content-Type: application/json" \
  -d '{"sampleRate": 6000000}'

Common Issues

Issue: Audio Too Quiet

Solutions:

Increase gain on capture
Increase agcTargetDb (e.g., -15 instead of -20)
Check antenna connection

Issue: Audio Distorted

Solutions:

Reduce gain on capture
Lower agcTargetDb (e.g., -25 instead of -20)
Enable de-emphasis for FM

Issue: Too Much Background Noise

Solutions:

Increase squelchDb (less negative, e.g., -40 instead of -60)
Add notch filters for specific interference
Enable noise blanker

Issue: Signal Cutting In/Out

Solutions:

Lower squelchDb (more negative)
Adjust AGC attack/release times
Check if frequency offset is correct

Issue: IQ Overflows (RTL-SDR)

Solutions:

Use stable sample rate (1.024 MHz, 2.048 MHz, or 2.4 MHz)
Avoid sample rates below 900 kHz
Check USB connection quality

Issue: Aliasing at Spectrum Edges

Solutions:

Reduce bandwidth to ≤80% of sample rate
Increase sample rate if wider bandwidth needed
Use appropriate IF filter settings

Files in This Skill

SKILL.md: This file - instructions for using the skill
adjust_settings.py: Helper script for adjusting radio settings