Add Airspy SDR support and persist GPS coordinates

Airspy support:
- Add AIRSPY to SDRType enum and driver mappings
- Create AirspyCommandBuilder using SoapySDR tools (rx_fm, readsb, rtl_433)
- Register in SDRFactory and add to hardware type dropdown
- Supports Airspy R2/Mini (24MHz-1.8GHz) and HF+ devices

GPS coordinate persistence:
- Save observer location to localStorage when manually entered or via geolocation
- Restore saved coordinates on page load in both index.html and adsb_dashboard.html
- Coordinates are shared between both pages

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

utils/sdr/__init__.py

@@ -30,6 +30,7 @@ from .detection import detect_all_devices
 from .rtlsdr import RTLSDRCommandBuilder
 from .limesdr import LimeSDRCommandBuilder
 from .hackrf import HackRFCommandBuilder
+from .airspy import AirspyCommandBuilder
 from .validation import (
     SDRValidationError,
     validate_frequency,
@@ -49,6 +50,7 @@ class SDRFactory:
         SDRType.RTL_SDR: RTLSDRCommandBuilder,
         SDRType.LIME_SDR: LimeSDRCommandBuilder,
         SDRType.HACKRF: HackRFCommandBuilder,
+        SDRType.AIRSPY: AirspyCommandBuilder,
     }
 
     @classmethod
@@ -214,6 +216,7 @@ __all__ = [
     'RTLSDRCommandBuilder',
     'LimeSDRCommandBuilder',
     'HackRFCommandBuilder',
+    'AirspyCommandBuilder',
     # Validation
     'SDRValidationError',
     'validate_frequency',

utils/sdr/airspy.py

@@ -0,0 +1,153 @@
+"""
+Airspy command builder implementation.
+
+Uses SoapySDR-based tools for FM demodulation and signal capture.
+Airspy R2/Mini supports 24 MHz to 1.8 GHz frequency range.
+Airspy HF+ supports 9 kHz - 31 MHz and 60-260 MHz.
+"""
+
+from __future__ import annotations
+
+from typing import Optional
+
+from .base import CommandBuilder, SDRCapabilities, SDRDevice, SDRType
+
+
+class AirspyCommandBuilder(CommandBuilder):
+    """Airspy command builder using SoapySDR tools."""
+
+    # Airspy R2/Mini capabilities (most common)
+    # HF+ has different range but same interface
+    CAPABILITIES = SDRCapabilities(
+        sdr_type=SDRType.AIRSPY,
+        freq_min_mhz=24.0,       # 24 MHz (HF+ goes lower)
+        freq_max_mhz=1800.0,     # 1.8 GHz
+        gain_min=0.0,
+        gain_max=45.0,           # LNA (0-15) + Mixer (0-15) + VGA (0-15)
+        sample_rates=[2500000, 3000000, 6000000, 10000000],
+        supports_bias_t=True,
+        supports_ppm=False,      # Airspy has TCXO, no PPM needed
+        tx_capable=False
+    )
+
+    def _build_device_string(self, device: SDRDevice) -> str:
+        """Build SoapySDR device string for Airspy."""
+        driver = device.driver if device.driver in ('airspy', 'airspyhf') else 'airspy'
+        if device.serial and device.serial != 'N/A':
+            return f'driver={driver},serial={device.serial}'
+        return f'driver={driver}'
+
+    def _format_gain(self, gain: float) -> str:
+        """
+        Format gain string for Airspy.
+
+        Airspy has three gain stages:
+        - LNA: 0-15 dB
+        - Mixer: 0-15 dB
+        - VGA: 0-15 dB
+
+        This distributes the requested gain across stages.
+        """
+        if gain <= 15:
+            return f'LNA={int(gain)},MIX=0,VGA=0'
+        elif gain <= 30:
+            return f'LNA=15,MIX={int(gain - 15)},VGA=0'
+        else:
+            vga = min(15, int(gain - 30))
+            return f'LNA=15,MIX=15,VGA={vga}'
+
+    def build_fm_demod_command(
+        self,
+        device: SDRDevice,
+        frequency_mhz: float,
+        sample_rate: int = 22050,
+        gain: Optional[float] = None,
+        ppm: Optional[int] = None,
+        modulation: str = "fm",
+        squelch: Optional[int] = None
+    ) -> list[str]:
+        """
+        Build SoapySDR rx_fm command for FM demodulation.
+
+        For pager decoding with Airspy.
+        """
+        device_str = self._build_device_string(device)
+
+        cmd = [
+            'rx_fm',
+            '-d', device_str,
+            '-f', f'{frequency_mhz}M',
+            '-M', modulation,
+            '-s', str(sample_rate),
+        ]
+
+        if gain is not None and gain > 0:
+            cmd.extend(['-g', self._format_gain(gain)])
+
+        if squelch is not None and squelch > 0:
+            cmd.extend(['-l', str(squelch)])
+
+        # Output to stdout
+        cmd.append('-')
+
+        return cmd
+
+    def build_adsb_command(
+        self,
+        device: SDRDevice,
+        gain: Optional[float] = None
+    ) -> list[str]:
+        """
+        Build dump1090/readsb command with SoapySDR support for ADS-B decoding.
+
+        Uses readsb which has better SoapySDR support.
+        """
+        device_str = self._build_device_string(device)
+
+        cmd = [
+            'readsb',
+            '--net',
+            '--device-type', 'soapysdr',
+            '--device', device_str,
+            '--quiet'
+        ]
+
+        if gain is not None:
+            cmd.extend(['--gain', str(int(gain))])
+
+        return cmd
+
+    def build_ism_command(
+        self,
+        device: SDRDevice,
+        frequency_mhz: float = 433.92,
+        gain: Optional[float] = None,
+        ppm: Optional[int] = None
+    ) -> list[str]:
+        """
+        Build rtl_433 command with SoapySDR support for ISM band decoding.
+
+        rtl_433 has native SoapySDR support via -d flag.
+        """
+        device_str = self._build_device_string(device)
+
+        cmd = [
+            'rtl_433',
+            '-d', device_str,
+            '-f', f'{frequency_mhz}M',
+            '-F', 'json'
+        ]
+
+        if gain is not None and gain > 0:
+            cmd.extend(['-g', str(int(gain))])
+
+        return cmd
+
+    def get_capabilities(self) -> SDRCapabilities:
+        """Return Airspy capabilities."""
+        return self.CAPABILITIES
+
+    @classmethod
+    def get_sdr_type(cls) -> SDRType:
+        """Return SDR type."""
+        return SDRType.AIRSPY

utils/sdr/base.py

@@ -18,6 +18,7 @@ class SDRType(Enum):
     RTL_SDR = "rtlsdr"
     LIME_SDR = "limesdr"
     HACKRF = "hackrf"
+    AIRSPY = "airspy"
     # Future support
     # USRP = "usrp"
     # BLADE_RF = "bladerf"

utils/sdr/detection.py

@@ -28,11 +28,13 @@ def _get_capabilities_for_type(sdr_type: SDRType) -> SDRCapabilities:
     from .rtlsdr import RTLSDRCommandBuilder
     from .limesdr import LimeSDRCommandBuilder
     from .hackrf import HackRFCommandBuilder
+    from .airspy import AirspyCommandBuilder
 
     builders = {
         SDRType.RTL_SDR: RTLSDRCommandBuilder,
         SDRType.LIME_SDR: LimeSDRCommandBuilder,
         SDRType.HACKRF: HackRFCommandBuilder,
+        SDRType.AIRSPY: AirspyCommandBuilder,
     }
 
     builder_class = builders.get(sdr_type)
@@ -60,6 +62,8 @@ def _driver_to_sdr_type(driver: str) -> Optional[SDRType]:
         'lime': SDRType.LIME_SDR,
         'limesdr': SDRType.LIME_SDR,
         'hackrf': SDRType.HACKRF,
+        'airspy': SDRType.AIRSPY,
+        'airspyhf': SDRType.AIRSPY,  # Airspy HF+ uses same builder
         # Future support
         # 'uhd': SDRType.USRP,
         # 'bladerf': SDRType.BLADE_RF,