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Add multi-SDR support to WeFax decoder (HackRF, LimeSDR, Airspy, SDRPlay)

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Replace hardcoded rtl_fm with SDRFactory abstraction layer so WeFax works
with any supported SDR hardware, matching the pattern used by APRS and
other modes. RTL-SDR direct sampling flag preserved for HF reception.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
Smittix
2026-02-25 16:45:07 +00:00
parent 2202e3ed98
commit f3158cbb69
4 changed files with 295 additions and 269 deletions
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utils/wefax.py
+39 -22
View File
@@ -1,10 +1,11 @@
"""WeFax (Weather Fax) decoder.
Decodes HF radiofax (weather fax) transmissions using RTL-SDR direct
sampling mode. The decoder implements the standard WeFax AM protocol:
Decodes HF radiofax (weather fax) transmissions using any supported SDR
(RTL-SDR, HackRF, LimeSDR, Airspy, SDRPlay) via the SDRFactory
abstraction layer. The decoder implements the standard WeFax AM protocol:
carrier 1900 Hz, deviation +/-400 Hz (black=1500, white=2300).
Pipeline: rtl_fm -M usb -E direct2 -> stdout PCM -> Python DSP state machine
Pipeline: rtl_fm/rx_fm -M usb -> stdout PCM -> Python DSP state machine
State machine: SCANNING -> PHASING -> RECEIVING -> COMPLETE
"""
@@ -30,6 +31,7 @@ import numpy as np
from utils.dependencies import get_tool_path
from utils.logging import get_logger
from utils.sdr import SDRFactory, SDRType
logger = get_logger('intercept.wefax')
@@ -262,17 +264,19 @@ class WeFaxDecoder:
ioc: int = DEFAULT_IOC,
lpm: int = DEFAULT_LPM,
direct_sampling: bool = True,
sdr_type: str = 'rtlsdr',
) -> bool:
"""Start WeFax decoder.
Args:
frequency_khz: Frequency in kHz (e.g. 4298 for NOJ).
station: Station callsign for metadata.
device_index: RTL-SDR device index.
device_index: SDR device index.
gain: Receiver gain in dB.
ioc: Index of Cooperation (576 or 288).
lpm: Lines per minute (120 or 60).
direct_sampling: Enable RTL-SDR direct sampling for HF.
sdr_type: SDR hardware type (rtlsdr, hackrf, limesdr, airspy, sdrplay).
Returns:
True if started successfully.
@@ -288,6 +292,7 @@ class WeFaxDecoder:
self._device_index = device_index
self._gain = gain
self._direct_sampling = direct_sampling
self._sdr_type = sdr_type
self._sample_rate = DEFAULT_SAMPLE_RATE
try:
@@ -312,27 +317,39 @@ class WeFaxDecoder:
return False
def _start_pipeline(self) -> None:
"""Start rtl_fm subprocess in USB mode for WeFax."""
rtl_fm_path = get_tool_path('rtl_fm')
if not rtl_fm_path:
raise RuntimeError('rtl_fm not found')
"""Start SDR FM demod subprocess in USB mode for WeFax."""
try:
sdr_type_enum = SDRType(self._sdr_type)
except ValueError:
sdr_type_enum = SDRType.RTL_SDR
freq_hz = int(self._frequency_khz * 1000)
# Validate that the required tool is available
if sdr_type_enum == SDRType.RTL_SDR:
if not get_tool_path('rtl_fm'):
raise RuntimeError('rtl_fm not found')
else:
if not get_tool_path('rx_fm'):
raise RuntimeError('rx_fm not found (required for non-RTL-SDR devices)')
rtl_cmd = [
rtl_fm_path,
'-d', str(self._device_index),
'-f', str(freq_hz),
'-M', 'usb',
'-s', str(self._sample_rate),
'-r', str(self._sample_rate),
'-g', str(self._gain),
]
sdr_device = SDRFactory.create_default_device(
sdr_type_enum, index=self._device_index)
builder = SDRFactory.get_builder(sdr_type_enum)
rtl_cmd = builder.build_fm_demod_command(
device=sdr_device,
frequency_mhz=self._frequency_khz / 1000.0,
sample_rate=self._sample_rate,
gain=self._gain,
modulation='usb',
)
if self._direct_sampling:
rtl_cmd.extend(['-E', 'direct2'])
rtl_cmd.append('-')
# RTL-SDR: append direct sampling flag for HF reception
if sdr_type_enum == SDRType.RTL_SDR and self._direct_sampling:
# Insert before trailing '-' stdout marker
if rtl_cmd and rtl_cmd[-1] == '-':
rtl_cmd.insert(-1, '-E')
rtl_cmd.insert(-1, 'direct2')
else:
rtl_cmd.extend(['-E', 'direct2', '-'])
logger.info(f"Starting rtl_fm: {' '.join(rtl_cmd)}")