SDR Setup Guide

Complete guide for setting up Software Defined Radio (SDR) receivers with EAS Station™

Quick Navigation

• Hardware Guide - Choosing the right SDR
• Setup Flowchart - Visual overview
• Web UI Setup - Easiest configuration method
• Troubleshooting - Fix common issues

Visual Setup Guide

For a complete visual overview of the SDR setup process:

View full-size diagram

Quick Start

What's Included

SoapySDR, RTL-SDR, and Airspy drivers are pre-installed in the installation:

• ✅ SoapySDR core libraries
• ✅ RTL-SDR drivers (default)
• ✅ Airspy drivers (default)
• ✅ USB device passthrough (pre-configured)
• ✅ No .env configuration needed

Setup Steps

1. Plug in your SDR device

   # Verify device is detected on host
   lsusb | grep -i rtl  # For RTL-SDR
   lsusb | grep -i airspy  # For Airspy
   

2. Start the services

   sudo systemctl start eas-station-sdr eas-station-audio
   

3. Verify SDR detection

   # Check SoapySDR can see the device
   SoapySDRUtil --find
   
   # Run diagnostic script
   python3 scripts/sdr_diagnostics.py
   

4. Configure in Web UI

   • Open http://localhost (or your server IP)
   • Navigate to Settings → Radio Receivers
   • Click Discover Devices
   • Click Add This Device on your SDR
   • Apply a preset (NOAA Weather Radio recommended)
   • Save and enable

Done! Your SDR should now show "Locked" status.

Hardware Requirements

Supported SDR Devices

Recommended starter: RTL-SDR Blog V3 ($30) with bias-tee for powered antennas

Antenna Requirements

For NOAA Weather Radio (162 MHz):

Signal improvement tips:

• Place antenna near window or outdoors
• Higher is better (roof/attic mounting)
• Keep away from computers and USB hubs (RF interference)
• Use quality coaxial cable (low-loss RG-6 or LMR-400)

Software Installation

bare metal deployment (Recommended)

No installation needed! SoapySDR and all drivers are built into the installation.

The image includes:

• SoapySDR core libraries and Python bindings
• RTL-SDR and Airspy drivers (via SOAPYSDR_DRIVERS build arg)
• USB device support (libusb)
• NumPy for signal processing

devices:
  - /dev/bus/usb:/dev/bus/usb
privileged: true

Optional: Customize driver installation

To reduce build time, install only the drivers you need in .env:

# Only RTL-SDR (faster builds)
SOAPYSDR_DRIVERS=rtlsdr

# Both RTL-SDR and Airspy (default)
SOAPYSDR_DRIVERS=rtlsdr,airspy

Verify USB Access

# 1. Check if SDR is detected on host
lsusb | grep -i rtl  # Or grep -i airspy

# Expected output:
# Bus 001 Device 005: ID 0bda:2838 Realtek Semiconductor Corp. RTL2838 DVB-T

# 2. Verify the service user can access USB devices
groups eas-station | grep plugdev

# 3. Test SoapySDR detection
SoapySDRUtil --find

Troubleshooting USB Issues

Problem: No devices found

1. Kernel driver conflict (RTL-SDR only)

   The DVB-T TV tuner driver blocks RTL-SDR access:

   # On host, create /etc/modprobe.d/blacklist-rtl.conf:
   sudo tee /etc/modprobe.d/blacklist-rtl.conf <<EOF
   blacklist dvb_usb_rtl28xxu
   blacklist rtl2832
   blacklist rtl2830
   EOF
   
   # Unload the module
   sudo modprobe -r dvb_usb_rtl28xxu
   
   # Reboot to make permanent
   sudo reboot
   

2. Service needs restart

   sudo systemctl restart eas-station-sdr
   

3. USB device path changed

   udev re-enumerates USB devices automatically; if the SDR was replugged, restart the SDR service as above.

Web UI Configuration

Easiest way to configure SDRs

Step-by-Step Setup

1. Access Radio Settings

1. Log into EAS Station™ web interface
2. Navigate to Settings → Radio Receivers

2. Run Diagnostics

1. Click Run Diagnostics button
2. Verify all checks pass:
   • ✓ SoapySDR is installed
   • ✓ NumPy is installed
   • ✓ RTL-SDR or Airspy driver available
   • ✓ At least 1 device detected

If diagnostics fail → Troubleshooting

3. Discover and Add Device

1. Click Discover Devices
2. Review detected SDRs
3. Click Add This Device on your SDR
4. Form pre-fills with device info

4. Apply Preset (Recommended)

1. Click Use Preset
2. Choose:
   • NOAA Weather Radio (RTL-SDR) - For RTL-SDR dongles
   • NOAA Weather Radio (Airspy) - For Airspy receivers
3. Click Use This Preset

5. Set Your Local Frequency

Find your nearest NOAA Weather Radio station: https://www.weather.gov/nwr/station_listing

NOAA Frequencies:

Convert to Hz: Multiply MHz × 1,000,000 Example: 162.550 MHz = 162550000 Hz

6. Enable and Monitor

1. Check Enabled and Auto-start
2. Click Save Receiver
3. Wait for Locked status (green badge)
4. Check signal strength (should be > 0.1 dBFS for good reception)

Manual Configuration

Configuration Fields

Gain Settings Guide

RTL-SDR:

• Range: 0-50 dB
• Start with: 49.6 dB (maximum sensitivity)
• Adjust down if signal is too strong (> 1.0 dBFS)

Airspy:

• Range: 0-21 dB (linearity mode) or 0-15 dB (sensitivity mode)
• Start with: 21 dB
• Airspy has automatic gain control (AGC) option

Too much gain = Overload, distortion Too little gain = Weak signal, poor decoding

Testing and Verification

Using Diagnostic Tools

# Full diagnostic check

# Enumerate all devices

# Check driver capabilities

# Test sample capture (5 seconds at 162.55 MHz)
  --test-capture --driver rtlsdr --frequency 162550000 --duration 5

# Show available presets

Web UI Status Check

1. Navigate to Settings → Radio Receivers
2. Check Receiver Status panel:
   • Locked count > 0
   • Green "Locked" badges in receiver table
   • Signal strength displayed (dBFS)

Expected Signal Levels

Troubleshooting

"No SDR Devices Found"

Possible causes and solutions:

1. SDR not plugged in

   • Check USB connection
   • Try different USB port (USB 2.0 often better than USB 3.0)
   • Verify with lsusb on host

2. Kernel driver conflict (RTL-SDR)

   • Blacklist DVB-T drivers

3. SoapySDR bindings missing from the virtual environment

   bash scripts/fix_soapysdr_venv.sh
   

4. Restart services after plugging in device

   sudo systemctl restart eas-station-sdr eas-station-audio
   

"Receiver shows 'No lock' status"

1. Wrong frequency

   • Verify correct NOAA station: https://www.weather.gov/nwr/station_listing
   • Double-check frequency entered in Hz (not MHz)

2. Weak signal

   • Improve antenna (see Hardware Requirements)
   • Move antenna to window or outdoors
   • Increase gain (but watch for overload)

3. No antenna connected

   • Ensure antenna is firmly attached to SMA connector

4. Interference

   • Move SDR away from computers, power supplies
   • Use shielded USB cable
   • Try powered USB hub for better power delivery

"Signal strength is 0 or very low"

1. Check antenna connection - Firm SMA connection
2. Verify frequency - Matches local NOAA station
3. Increase gain - Try 49.6 dB for RTL-SDR, 21 dB for Airspy
4. Test with FM radio - Tune to 88-108 MHz to verify hardware works

"Permission denied" errors

devices:
  - /dev/bus/usb:/dev/bus/usb
cap_add:
  - SYS_RAWIO

If still having issues, add user to plugdev group:

sudo usermod -aG plugdev $USER
# Log out and back in

Advanced Topics

Multiple SDR Receivers

Run multiple SDRs simultaneously:

Use cases:

• Monitor multiple NOAA frequencies
• Redundancy (backup receivers)
• Different signal types (weather + FM broadcast)

Configuration:

1. All SDRs will appear in Discover Devices
2. Add each with unique names
3. Configure different frequencies
4. Each runs independently

Example setup:

• Receiver 1: rtlsdr_wx → 162.550 MHz (NOAA)
• Receiver 2: rtlsdr_fm → 95500000 Hz (FM broadcast)
• Receiver 3: airspy_backup → 162.550 MHz (backup)

Capture Modes

Configure in .env:

# IQ mode: Complex 32-bit I/Q samples (for offline analysis)
RADIO_CAPTURE_MODE=iq

# PCM mode: Float32 interleaved I/Q (for direct audio decoders)
RADIO_CAPTURE_MODE=pcm

Capture Duration

# Capture 30 seconds when SAME burst detected
RADIO_CAPTURE_DURATION=30

Signal Analysis Tools

Analyze captured IQ files with:

• GNU Radio - Signal processing and demodulation
• inspectrum - Visual spectrum analyzer
• Custom Python - NumPy/SciPy analysis

Performance Optimization

1. Use USB 3.0 ports for higher sample rates
2. Avoid USB hubs - Direct motherboard connection
3. Monitor CPU usage - High sample rates increase CPU load
4. Check for USB dropouts:

   dmesg | grep -i usb
   

Security Considerations

For dedicated SDR stations:

• /dev/bus/usb:/dev/bus/usb passthrough is safe
• No other sensitive USB devices connected

For shared systems:

• Consider specific device passthrough
• Use udev rules to restrict by vendor/product ID

Getting Help

If you're still having issues:

1. Check logs: sudo journalctl -u eas-station-sdr -n 100
2. Run diagnostics: Web UI or python scripts/sdr_diagnostics.py
3. GitHub Issues: https://github.com/KR8MER/eas-station/issues

When reporting issues, include:

• SDR model and driver (RTL-SDR, Airspy, etc.)
• Output of lsusb on host
• Output of SoapySDRUtil --find
• Diagnostic script output
• Relevant log excerpts

Additional Resources

• SoapySDR Documentation: https://github.com/pothosware/SoapySDR/wiki
• RTL-SDR Guide: https://www.rtl-sdr.com/about-rtl-sdr/
• Airspy Documentation: https://airspy.com/
• NOAA Weather Radio: https://www.weather.gov/nwr/
• EAS/SAME Protocol: https://en.wikipedia.org/wiki/Specific_Area_Message_Encoding

Last Updated: 2025-11-30