Radio Tuner

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)

Channel Settings (Demodulator-level)

Filter Settings

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

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

Best Practices to Avoid Warnings

1. 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}'
   

2. 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}'
   

3. 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