feat: Add VDL2 mode and ACARS standalone frontend

Add VDL2 (VHF Digital Link Mode 2) decoding via dumpvdl2 as a new mode,
and promote ACARS from ADS-B-dashboard-only to a first-class standalone
mode in the main SPA. Both aviation datalink modes now have full nav
entries, sidebar partials with region-based frequency selectors, and
SSE streaming. VDL2 also integrated into the ADS-B dashboard as a
collapsible sidebar alongside ACARS.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Dockerfile

@@ -95,6 +95,8 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     libfftw3-dev \
     liblapack-dev \
     libcodec2-dev \
+    libglib2.0-dev \
+    libxml2-dev \
     # Build dump1090
     && cd /tmp \
     && git clone --depth 1 https://github.com/flightaware/dump1090.git \
@@ -141,6 +143,25 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     && make \
     && cp acarsdec /usr/bin/acarsdec \
     && rm -rf /tmp/acarsdec \
+    # Build libacars (required by dumpvdl2)
+    && cd /tmp \
+    && git clone --depth 1 https://github.com/szpajder/libacars.git \
+    && cd libacars \
+    && mkdir build && cd build \
+    && cmake .. \
+    && make \
+    && make install \
+    && ldconfig \
+    && rm -rf /tmp/libacars \
+    # Build dumpvdl2 (VDL2 aircraft datalink decoder)
+    && cd /tmp \
+    && git clone --depth 1 https://github.com/szpajder/dumpvdl2.git \
+    && cd dumpvdl2 \
+    && mkdir build && cd build \
+    && cmake .. \
+    && make \
+    && cp src/dumpvdl2 /usr/bin/dumpvdl2 \
+    && rm -rf /tmp/dumpvdl2 \
     # Build slowrx (SSTV decoder) — pinned to known-good commit
     && cd /tmp \
     && git clone https://github.com/windytan/slowrx.git \

app.py

@@ -150,6 +150,11 @@ acars_process = None
 acars_queue = queue.Queue(maxsize=QUEUE_MAX_SIZE)
 acars_lock = threading.Lock()
 
+# VDL2 aircraft datalink
+vdl2_process = None
+vdl2_queue = queue.Queue(maxsize=QUEUE_MAX_SIZE)
+vdl2_lock = threading.Lock()
+
 # APRS amateur radio tracking
 aprs_process = None
 aprs_rtl_process = None
@@ -680,6 +685,7 @@ def health_check() -> Response:
             'adsb': adsb_process is not None and (adsb_process.poll() is None if adsb_process else False),
             'ais': ais_process is not None and (ais_process.poll() is None if ais_process else False),
             'acars': acars_process is not None and (acars_process.poll() is None if acars_process else False),
+            'vdl2': vdl2_process is not None and (vdl2_process.poll() is None if vdl2_process else False),
             'aprs': aprs_process is not None and (aprs_process.poll() is None if aprs_process else False),
             'wifi': wifi_process is not None and (wifi_process.poll() is None if wifi_process else False),
             'bluetooth': bt_process is not None and (bt_process.poll() is None if bt_process else False),
@@ -702,6 +708,7 @@ def health_check() -> Response:
 def kill_all() -> Response:
     """Kill all decoder, WiFi, and Bluetooth processes."""
     global current_process, sensor_process, wifi_process, adsb_process, ais_process, acars_process
+    global vdl2_process
     global aprs_process, aprs_rtl_process, dsc_process, dsc_rtl_process, bt_process
     global dmr_process, dmr_rtl_process
 
@@ -714,7 +721,7 @@ def kill_all() -> Response:
     processes_to_kill = [
         'rtl_fm', 'multimon-ng', 'rtl_433',
         'airodump-ng', 'aireplay-ng', 'airmon-ng',
-        'dump1090', 'acarsdec', 'direwolf', 'AIS-catcher',
+        'dump1090', 'acarsdec', 'dumpvdl2', 'direwolf', 'AIS-catcher',
         'hcitool', 'bluetoothctl', 'satdump', 'dsd',
         'rtl_tcp', 'rtl_power', 'rtlamr', 'ffmpeg',
         'hackrf_transfer', 'hackrf_sweep'
@@ -751,6 +758,10 @@ def kill_all() -> Response:
     with acars_lock:
         acars_process = None
 
+    # Reset VDL2 state
+    with vdl2_lock:
+        vdl2_process = None
+
     # Reset APRS state
     with aprs_lock:
         aprs_process = None

routes/__init__.py

@@ -13,6 +13,7 @@ def register_blueprints(app):
     from .ais import ais_bp
     from .dsc import dsc_bp
     from .acars import acars_bp
+    from .vdl2 import vdl2_bp
     from .aprs import aprs_bp
     from .satellite import satellite_bp
     from .gps import gps_bp
@@ -46,6 +47,7 @@ def register_blueprints(app):
     app.register_blueprint(ais_bp)
     app.register_blueprint(dsc_bp)  # VHF DSC maritime distress
     app.register_blueprint(acars_bp)
+    app.register_blueprint(vdl2_bp)
     app.register_blueprint(aprs_bp)
     app.register_blueprint(satellite_bp)
     app.register_blueprint(gps_bp)

routes/vdl2.py

@@ -0,0 +1,357 @@
+"""VDL2 aircraft datalink routes."""
+
+from __future__ import annotations
+
+import json
+import queue
+import shutil
+import subprocess
+import threading
+import time
+from datetime import datetime
+from typing import Generator
+
+from flask import Blueprint, jsonify, request, Response
+
+import app as app_module
+from utils.logging import sensor_logger as logger
+from utils.validation import validate_device_index, validate_gain, validate_ppm
+from utils.sdr import SDRFactory, SDRType
+from utils.sse import format_sse
+from utils.event_pipeline import process_event
+from utils.constants import (
+    PROCESS_TERMINATE_TIMEOUT,
+    SSE_KEEPALIVE_INTERVAL,
+    SSE_QUEUE_TIMEOUT,
+    PROCESS_START_WAIT,
+)
+from utils.process import register_process, unregister_process
+
+vdl2_bp = Blueprint('vdl2', __name__, url_prefix='/vdl2')
+
+# Default VDL2 frequencies (MHz) - common worldwide
+DEFAULT_VDL2_FREQUENCIES = [
+    '136975000',  # Primary worldwide
+    '136725000',  # Europe
+    '136775000',  # Europe
+    '136800000',  # Multi-region
+    '136875000',  # Multi-region
+]
+
+# Message counter for statistics
+vdl2_message_count = 0
+vdl2_last_message_time = None
+
+# Track which device is being used
+vdl2_active_device: int | None = None
+
+
+def find_dumpvdl2():
+    """Find dumpvdl2 binary."""
+    return shutil.which('dumpvdl2')
+
+
+def stream_vdl2_output(process: subprocess.Popen) -> None:
+    """Stream dumpvdl2 JSON output to queue."""
+    global vdl2_message_count, vdl2_last_message_time
+
+    try:
+        app_module.vdl2_queue.put({'type': 'status', 'status': 'started'})
+
+        for line in iter(process.stdout.readline, b''):
+            line = line.decode('utf-8', errors='replace').strip()
+            if not line:
+                continue
+
+            try:
+                data = json.loads(line)
+
+                # Add our metadata
+                data['type'] = 'vdl2'
+                data['timestamp'] = datetime.utcnow().isoformat() + 'Z'
+
+                # Update stats
+                vdl2_message_count += 1
+                vdl2_last_message_time = time.time()
+
+                app_module.vdl2_queue.put(data)
+
+                # Log if enabled
+                if app_module.logging_enabled:
+                    try:
+                        with open(app_module.log_file_path, 'a') as f:
+                            ts = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
+                            f.write(f"{ts} | VDL2 | {json.dumps(data)}\n")
+                    except Exception:
+                        pass
+
+            except json.JSONDecodeError:
+                # Not JSON - could be status message
+                if line:
+                    logger.debug(f"dumpvdl2 non-JSON: {line[:100]}")
+
+    except Exception as e:
+        logger.error(f"VDL2 stream error: {e}")
+        app_module.vdl2_queue.put({'type': 'error', 'message': str(e)})
+    finally:
+        global vdl2_active_device
+        # Ensure process is terminated
+        try:
+            process.terminate()
+            process.wait(timeout=2)
+        except Exception:
+            try:
+                process.kill()
+            except Exception:
+                pass
+        unregister_process(process)
+        app_module.vdl2_queue.put({'type': 'status', 'status': 'stopped'})
+        with app_module.vdl2_lock:
+            app_module.vdl2_process = None
+        # Release SDR device
+        if vdl2_active_device is not None:
+            app_module.release_sdr_device(vdl2_active_device)
+            vdl2_active_device = None
+
+
+@vdl2_bp.route('/tools')
+def check_vdl2_tools() -> Response:
+    """Check for VDL2 decoding tools."""
+    has_dumpvdl2 = find_dumpvdl2() is not None
+
+    return jsonify({
+        'dumpvdl2': has_dumpvdl2,
+        'ready': has_dumpvdl2
+    })
+
+
+@vdl2_bp.route('/status')
+def vdl2_status() -> Response:
+    """Get VDL2 decoder status."""
+    running = False
+    if app_module.vdl2_process:
+        running = app_module.vdl2_process.poll() is None
+
+    return jsonify({
+        'running': running,
+        'message_count': vdl2_message_count,
+        'last_message_time': vdl2_last_message_time,
+        'queue_size': app_module.vdl2_queue.qsize()
+    })
+
+
+@vdl2_bp.route('/start', methods=['POST'])
+def start_vdl2() -> Response:
+    """Start VDL2 decoder."""
+    global vdl2_message_count, vdl2_last_message_time, vdl2_active_device
+
+    with app_module.vdl2_lock:
+        if app_module.vdl2_process and app_module.vdl2_process.poll() is None:
+            return jsonify({
+                'status': 'error',
+                'message': 'VDL2 decoder already running'
+            }), 409
+
+    # Check for dumpvdl2
+    dumpvdl2_path = find_dumpvdl2()
+    if not dumpvdl2_path:
+        return jsonify({
+            'status': 'error',
+            'message': 'dumpvdl2 not found. Install from: https://github.com/szpajder/dumpvdl2'
+        }), 400
+
+    data = request.json or {}
+
+    # Validate inputs
+    try:
+        device = validate_device_index(data.get('device', '0'))
+        gain = validate_gain(data.get('gain', '40'))
+        ppm = validate_ppm(data.get('ppm', '0'))
+    except ValueError as e:
+        return jsonify({'status': 'error', 'message': str(e)}), 400
+
+    # Check if device is available
+    device_int = int(device)
+    error = app_module.claim_sdr_device(device_int, 'vdl2')
+    if error:
+        return jsonify({
+            'status': 'error',
+            'error_type': 'DEVICE_BUSY',
+            'message': error
+        }), 409
+
+    vdl2_active_device = device_int
+
+    # Get frequencies - use provided or defaults
+    # dumpvdl2 expects frequencies in Hz (integers)
+    frequencies = data.get('frequencies', DEFAULT_VDL2_FREQUENCIES)
+    if isinstance(frequencies, str):
+        frequencies = [f.strip() for f in frequencies.split(',')]
+
+    # Clear queue
+    while not app_module.vdl2_queue.empty():
+        try:
+            app_module.vdl2_queue.get_nowait()
+        except queue.Empty:
+            break
+
+    # Reset stats
+    vdl2_message_count = 0
+    vdl2_last_message_time = None
+
+    # Resolve SDR type for device selection
+    sdr_type_str = data.get('sdr_type', 'rtlsdr')
+    try:
+        sdr_type = SDRType(sdr_type_str)
+    except ValueError:
+        sdr_type = SDRType.RTL_SDR
+
+    is_soapy = sdr_type not in (SDRType.RTL_SDR,)
+
+    # Build dumpvdl2 command
+    # dumpvdl2 --output decoded:json --rtlsdr <device> --gain <gain> --correction <ppm> <freq1> <freq2> ...
+    cmd = [dumpvdl2_path]
+    cmd.extend(['--output', 'decoded:json'])
+
+    if is_soapy:
+        # SoapySDR device
+        sdr_device = SDRFactory.create_default_device(sdr_type, index=device_int)
+        builder = SDRFactory.get_builder(sdr_type)
+        device_str = builder._build_device_string(sdr_device)
+        cmd.extend(['--soapysdr', device_str])
+    else:
+        cmd.extend(['--rtlsdr', str(device)])
+
+    # Add gain
+    if gain and str(gain) != '0':
+        cmd.extend(['--gain', str(gain)])
+
+    # Add PPM correction if specified
+    if ppm and str(ppm) != '0':
+        cmd.extend(['--correction', str(ppm)])
+
+    # Add frequencies (dumpvdl2 takes them as positional args in Hz)
+    cmd.extend(frequencies)
+
+    logger.info(f"Starting VDL2 decoder: {' '.join(cmd)}")
+
+    try:
+        process = subprocess.Popen(
+            cmd,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+            start_new_session=True
+        )
+
+        # Wait briefly to check if process started
+        time.sleep(PROCESS_START_WAIT)
+
+        if process.poll() is not None:
+            # Process died - release device
+            if vdl2_active_device is not None:
+                app_module.release_sdr_device(vdl2_active_device)
+                vdl2_active_device = None
+            stderr = ''
+            if process.stderr:
+                stderr = process.stderr.read().decode('utf-8', errors='replace')
+            error_msg = 'dumpvdl2 failed to start'
+            if stderr:
+                error_msg += f': {stderr[:200]}'
+            logger.error(error_msg)
+            return jsonify({'status': 'error', 'message': error_msg}), 500
+
+        app_module.vdl2_process = process
+        register_process(process)
+
+        # Start output streaming thread
+        thread = threading.Thread(
+            target=stream_vdl2_output,
+            args=(process,),
+            daemon=True
+        )
+        thread.start()
+
+        return jsonify({
+            'status': 'started',
+            'frequencies': frequencies,
+            'device': device,
+            'gain': gain
+        })
+
+    except Exception as e:
+        # Release device on failure
+        if vdl2_active_device is not None:
+            app_module.release_sdr_device(vdl2_active_device)
+            vdl2_active_device = None
+        logger.error(f"Failed to start VDL2 decoder: {e}")
+        return jsonify({'status': 'error', 'message': str(e)}), 500
+
+
+@vdl2_bp.route('/stop', methods=['POST'])
+def stop_vdl2() -> Response:
+    """Stop VDL2 decoder."""
+    global vdl2_active_device
+
+    with app_module.vdl2_lock:
+        if not app_module.vdl2_process:
+            return jsonify({
+                'status': 'error',
+                'message': 'VDL2 decoder not running'
+            }), 400
+
+        try:
+            app_module.vdl2_process.terminate()
+            app_module.vdl2_process.wait(timeout=PROCESS_TERMINATE_TIMEOUT)
+        except subprocess.TimeoutExpired:
+            app_module.vdl2_process.kill()
+        except Exception as e:
+            logger.error(f"Error stopping VDL2: {e}")
+
+        app_module.vdl2_process = None
+
+    # Release device from registry
+    if vdl2_active_device is not None:
+        app_module.release_sdr_device(vdl2_active_device)
+        vdl2_active_device = None
+
+    return jsonify({'status': 'stopped'})
+
+
+@vdl2_bp.route('/stream')
+def stream_vdl2() -> Response:
+    """SSE stream for VDL2 messages."""
+    def generate() -> Generator[str, None, None]:
+        last_keepalive = time.time()
+
+        while True:
+            try:
+                msg = app_module.vdl2_queue.get(timeout=SSE_QUEUE_TIMEOUT)
+                last_keepalive = time.time()
+                try:
+                    process_event('vdl2', msg, msg.get('type'))
+                except Exception:
+                    pass
+                yield format_sse(msg)
+            except queue.Empty:
+                now = time.time()
+                if now - last_keepalive >= SSE_KEEPALIVE_INTERVAL:
+                    yield format_sse({'type': 'keepalive'})
+                    last_keepalive = now
+
+    response = Response(generate(), mimetype='text/event-stream')
+    response.headers['Cache-Control'] = 'no-cache'
+    response.headers['X-Accel-Buffering'] = 'no'
+    return response
+
+
+@vdl2_bp.route('/frequencies')
+def get_frequencies() -> Response:
+    """Get default VDL2 frequencies."""
+    return jsonify({
+        'default': DEFAULT_VDL2_FREQUENCIES,
+        'regions': {
+            'north_america': ['136975000', '136100000', '136650000', '136700000', '136800000'],
+            'europe': ['136975000', '136675000', '136725000', '136775000', '136825000'],
+            'asia_pacific': ['136975000', '136900000'],
+        }
+    })

setup.sh

@@ -226,6 +226,7 @@ check_tools() {
   check_optional "hackrf_sweep"    "HackRF spectrum analyzer" hackrf_sweep
   check_required "dump1090"    "ADS-B decoder" dump1090
   check_required "acarsdec"    "ACARS decoder" acarsdec
+  check_optional "dumpvdl2"    "VDL2 decoder" dumpvdl2
   check_required "AIS-catcher" "AIS vessel decoder" AIS-catcher aiscatcher
   check_optional "satdump" "Weather satellite decoder (NOAA/Meteor)" satdump
   echo
@@ -636,6 +637,80 @@ install_acarsdec_from_source_macos() {
   )
 }
 
+install_dumpvdl2_from_source_macos() {
+  info "Building dumpvdl2 from source (with libacars dependency)..."
+
+  brew_install cmake
+  brew_install librtlsdr
+  brew_install pkg-config
+  brew_install glib
+
+  (
+    tmp_dir="$(mktemp -d)"
+    trap 'rm -rf "$tmp_dir"' EXIT
+
+    HOMEBREW_PREFIX="$(brew --prefix)"
+    export PKG_CONFIG_PATH="${HOMEBREW_PREFIX}/lib/pkgconfig:${PKG_CONFIG_PATH:-}"
+    export CMAKE_PREFIX_PATH="${HOMEBREW_PREFIX}"
+
+    # Build libacars first
+    info "Cloning libacars..."
+    git clone --depth 1 https://github.com/szpajder/libacars.git "$tmp_dir/libacars" >/dev/null 2>&1 \
+      || { warn "Failed to clone libacars"; exit 1; }
+
+    cd "$tmp_dir/libacars"
+    mkdir -p build && cd build
+
+    info "Compiling libacars..."
+    build_log="$tmp_dir/libacars-build.log"
+    if cmake .. \
+         -DCMAKE_C_FLAGS="-I${HOMEBREW_PREFIX}/include" \
+         -DCMAKE_EXE_LINKER_FLAGS="-L${HOMEBREW_PREFIX}/lib" \
+         >"$build_log" 2>&1 \
+       && make >>"$build_log" 2>&1; then
+      if [[ -w /usr/local/lib ]]; then
+        make install >>"$build_log" 2>&1
+      else
+        refresh_sudo
+        $SUDO make install >>"$build_log" 2>&1
+      fi
+      ok "libacars installed"
+    else
+      warn "Failed to build libacars."
+      tail -20 "$build_log" | while IFS= read -r line; do warn "  $line"; done
+      exit 1
+    fi
+
+    # Build dumpvdl2
+    info "Cloning dumpvdl2..."
+    git clone --depth 1 https://github.com/szpajder/dumpvdl2.git "$tmp_dir/dumpvdl2" >/dev/null 2>&1 \
+      || { warn "Failed to clone dumpvdl2"; exit 1; }
+
+    cd "$tmp_dir/dumpvdl2"
+    mkdir -p build && cd build
+
+    info "Compiling dumpvdl2..."
+    build_log="$tmp_dir/dumpvdl2-build.log"
+    if cmake .. \
+         -DCMAKE_C_FLAGS="-I${HOMEBREW_PREFIX}/include" \
+         -DCMAKE_EXE_LINKER_FLAGS="-L${HOMEBREW_PREFIX}/lib" \
+         >"$build_log" 2>&1 \
+       && make >>"$build_log" 2>&1; then
+      if [[ -w /usr/local/bin ]]; then
+        install -m 0755 src/dumpvdl2 /usr/local/bin/dumpvdl2
+      else
+        refresh_sudo
+        $SUDO install -m 0755 src/dumpvdl2 /usr/local/bin/dumpvdl2
+      fi
+      ok "dumpvdl2 installed successfully from source"
+    else
+      warn "Failed to build dumpvdl2. VDL2 decoding will not be available."
+      warn "Build log (last 30 lines):"
+      tail -30 "$build_log" | while IFS= read -r line; do warn "  $line"; done
+    fi
+  )
+}
+
 install_aiscatcher_from_source_macos() {
   info "AIS-catcher not available via Homebrew. Building from source..."
 
@@ -874,6 +949,13 @@ install_macos_packages() {
     ok "acarsdec already installed"
   fi
 
+  progress "Installing dumpvdl2 (optional)"
+  if ! cmd_exists dumpvdl2; then
+    install_dumpvdl2_from_source_macos || warn "dumpvdl2 not available. VDL2 decoding will not be available."
+  else
+    ok "dumpvdl2 already installed"
+  fi
+
   progress "Installing AIS-catcher"
   if ! cmd_exists AIS-catcher && ! cmd_exists aiscatcher; then
     (brew_install aiscatcher) || install_aiscatcher_from_source_macos || warn "AIS-catcher not available"
@@ -1028,6 +1110,52 @@ install_acarsdec_from_source_debian() {
   )
 }
 
+install_dumpvdl2_from_source_debian() {
+  info "Building dumpvdl2 from source (with libacars dependency)..."
+
+  apt_install build-essential git cmake \
+    librtlsdr-dev libusb-1.0-0-dev libglib2.0-dev libxml2-dev
+
+  (
+    tmp_dir="$(mktemp -d)"
+    trap 'rm -rf "$tmp_dir"' EXIT
+
+    # Build libacars first
+    info "Cloning libacars..."
+    git clone --depth 1 https://github.com/szpajder/libacars.git "$tmp_dir/libacars" >/dev/null 2>&1 \
+      || { warn "Failed to clone libacars"; exit 1; }
+
+    cd "$tmp_dir/libacars"
+    mkdir -p build && cd build
+
+    info "Compiling libacars..."
+    if cmake .. >/dev/null 2>&1 && make >/dev/null 2>&1; then
+      $SUDO make install >/dev/null 2>&1
+      $SUDO ldconfig
+      ok "libacars installed"
+    else
+      warn "Failed to build libacars."
+      exit 1
+    fi
+
+    # Build dumpvdl2
+    info "Cloning dumpvdl2..."
+    git clone --depth 1 https://github.com/szpajder/dumpvdl2.git "$tmp_dir/dumpvdl2" >/dev/null 2>&1 \
+      || { warn "Failed to clone dumpvdl2"; exit 1; }
+
+    cd "$tmp_dir/dumpvdl2"
+    mkdir -p build && cd build
+
+    info "Compiling dumpvdl2..."
+    if cmake .. >/dev/null 2>&1 && make >/dev/null 2>&1; then
+      $SUDO install -m 0755 src/dumpvdl2 /usr/local/bin/dumpvdl2
+      ok "dumpvdl2 installed successfully."
+    else
+      warn "Failed to build dumpvdl2 from source. VDL2 decoding will not be available."
+    fi
+  )
+}
+
 install_aiscatcher_from_source_debian() {
   info "AIS-catcher not available via APT. Building from source..."
 
@@ -1344,6 +1472,13 @@ install_debian_packages() {
   fi
   cmd_exists acarsdec || install_acarsdec_from_source_debian
 
+  progress "Installing dumpvdl2 (optional)"
+  if ! cmd_exists dumpvdl2; then
+    install_dumpvdl2_from_source_debian || warn "dumpvdl2 not available. VDL2 decoding will not be available."
+  else
+    ok "dumpvdl2 already installed"
+  fi
+
   progress "Installing AIS-catcher"
   if ! cmd_exists AIS-catcher && ! cmd_exists aiscatcher; then
     install_aiscatcher_from_source_debian

static/css/adsb_dashboard.css

@@ -419,6 +419,163 @@ body {
     to { opacity: 1; transform: translateY(0); }
 }
 
+/* VDL2 sidebar (left of map, after ACARS) - Collapsible */
+.vdl2-sidebar {
+    display: none;
+    background: var(--bg-panel);
+    border-right: 1px solid var(--border-color);
+    flex-direction: row;
+    overflow: hidden;
+    height: 100%;
+    min-height: 0;
+}
+
+@media (min-width: 1024px) {
+    .vdl2-sidebar {
+        display: flex;
+        max-height: calc(100dvh - 160px);
+    }
+}
+
+.vdl2-collapse-btn {
+    width: 28px;
+    min-width: 28px;
+    background: var(--bg-card);
+    border: none;
+    border-left: 1px solid var(--border-color);
+    color: var(--accent-cyan);
+    cursor: pointer;
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    justify-content: center;
+    gap: 6px;
+    padding: 8px 0;
+    transition: background 0.2s;
+}
+
+.vdl2-collapse-btn:hover {
+    background: rgba(74, 158, 255, 0.2);
+}
+
+.vdl2-collapse-label {
+    writing-mode: vertical-rl;
+    text-orientation: mixed;
+    font-size: 9px;
+    font-weight: 600;
+    letter-spacing: 1px;
+    text-transform: uppercase;
+}
+
+.vdl2-sidebar.collapsed .vdl2-collapse-label {
+    display: block;
+}
+
+.vdl2-sidebar:not(.collapsed) .vdl2-collapse-label {
+    display: none;
+}
+
+#vdl2CollapseIcon {
+    font-size: 10px;
+    transition: transform 0.3s;
+}
+
+.vdl2-sidebar.collapsed #vdl2CollapseIcon {
+    transform: rotate(180deg);
+}
+
+.vdl2-sidebar-content {
+    width: 300px;
+    display: flex;
+    flex-direction: column;
+    overflow: hidden;
+    transition: width 0.3s ease, opacity 0.2s ease;
+    height: 100%;
+    min-height: 0;
+}
+
+.vdl2-sidebar.collapsed .vdl2-sidebar-content {
+    width: 0;
+    opacity: 0;
+    pointer-events: none;
+}
+
+.vdl2-sidebar .panel {
+    flex: 1;
+    display: flex;
+    flex-direction: column;
+    border: none;
+    border-radius: 0;
+    min-height: 0;
+    overflow: hidden;
+}
+
+.vdl2-sidebar .panel::before {
+    display: none;
+}
+
+.vdl2-sidebar .panel-header {
+    flex-shrink: 0;
+}
+
+.vdl2-sidebar #vdl2PanelContent {
+    display: flex;
+    flex-direction: column;
+    flex: 1;
+    min-height: 0;
+    overflow: hidden;
+}
+
+.vdl2-sidebar .vdl2-info,
+.vdl2-sidebar .vdl2-controls {
+    flex-shrink: 0;
+}
+
+.vdl2-sidebar .vdl2-messages {
+    flex: 1;
+    overflow-y: auto;
+    min-height: 0;
+}
+
+.vdl2-sidebar .vdl2-btn {
+    background: var(--accent-green);
+    border: none;
+    color: #fff;
+    padding: 6px 10px;
+    font-size: 10px;
+    font-weight: 600;
+    cursor: pointer;
+    transition: all 0.2s;
+    text-transform: uppercase;
+    letter-spacing: 1px;
+    border-radius: 4px;
+}
+
+.vdl2-sidebar .vdl2-btn:hover {
+    background: #1db954;
+    box-shadow: 0 0 10px rgba(34, 197, 94, 0.3);
+}
+
+.vdl2-sidebar .vdl2-btn.active {
+    background: var(--accent-red);
+}
+
+.vdl2-sidebar .vdl2-btn.active:hover {
+    background: #dc2626;
+    box-shadow: 0 0 10px rgba(239, 68, 68, 0.3);
+}
+
+.vdl2-message-item {
+    padding: 8px 10px;
+    border-bottom: 1px solid var(--border-color);
+    font-size: 10px;
+    animation: fadeIn 0.3s ease;
+}
+
+.vdl2-message-item:hover {
+    background: rgba(74, 158, 255, 0.05);
+}
+
 /* Panels */
 .panel {
     background: var(--bg-panel);
@@ -627,12 +784,18 @@ body {
 /* Selected aircraft panel */
 .selected-aircraft {
     flex-shrink: 0;
-    max-height: 480px;
+    max-height: 280px;
     overflow-y: auto;
 }
 
+@media (min-height: 900px) {
+    .selected-aircraft {
+        max-height: 340px;
+    }
+}
+
 .selected-info {
-    padding: 12px;
+    padding: 8px;
 }
 
 #aircraftPhotoContainer {
@@ -640,7 +803,7 @@ body {
 }
 
 #aircraftPhotoContainer img {
-    max-height: 140px;
+    max-height: 100px;
     width: 100%;
     object-fit: cover;
     border-radius: 6px;
@@ -649,24 +812,24 @@ body {
 
 .selected-callsign {
     font-family: 'Orbitron', monospace;
-    font-size: 20px;
+    font-size: 16px;
     font-weight: 700;
     color: var(--accent-cyan);
     text-shadow: 0 0 15px var(--accent-cyan);
     text-align: center;
-    margin-bottom: 12px;
+    margin-bottom: 6px;
 }
 
 .telemetry-grid {
     display: grid;
     grid-template-columns: repeat(2, 1fr);
-    gap: 6px;
+    gap: 4px;
 }
 
 .telemetry-item {
     background: rgba(0, 0, 0, 0.3);
     border-radius: 4px;
-    padding: 8px;
+    padding: 5px 8px;
     border-left: 2px solid var(--accent-cyan);
 }
 
@@ -778,7 +941,8 @@ body {
     background: var(--bg-panel);
     border-top: 1px solid rgba(74, 158, 255, 0.3);
     font-size: 11px;
-    overflow: hidden;
+    overflow-x: auto;
+    overflow-y: hidden;
 }
 
 .controls-bar > .control-group {
@@ -1489,6 +1653,10 @@ body {
     margin-top: 1px;
 }
 
+.strip-stat.source-stat .strip-value {
+    font-size: 11px;
+}
+
 .strip-stat.session-stat {
     background: rgba(34, 197, 94, 0.05);
     border-color: rgba(34, 197, 94, 0.2);
@@ -1779,6 +1947,9 @@ body {
 .strip-btn {
     position: relative;
     z-index: 10;
+    display: inline-flex;
+    align-items: center;
+    gap: 4px;
     background: rgba(74, 158, 255, 0.1);
     border: 1px solid rgba(74, 158, 255, 0.2);
     color: var(--text-primary);
@@ -1789,6 +1960,12 @@ body {
     cursor: pointer;
     transition: all 0.2s;
     white-space: nowrap;
+    text-decoration: none;
+}
+
+.strip-btn svg {
+    flex-shrink: 0;
+    opacity: 0.7;
 }
 
 .strip-btn:hover:not(:disabled) {

static/css/modes/vdl2.css

@@ -0,0 +1,31 @@
+/* VDL2 Mode Styles */
+
+/* VDL2 Status Indicator */
+.vdl2-status-dot.listening {
+    background: var(--accent-cyan) !important;
+    animation: vdl2-pulse 1.5s ease-in-out infinite;
+}
+.vdl2-status-dot.receiving {
+    background: var(--accent-green) !important;
+}
+.vdl2-status-dot.error {
+    background: var(--accent-red) !important;
+}
+@keyframes vdl2-pulse {
+    0%, 100% { opacity: 1; box-shadow: 0 0 0 0 rgba(74, 158, 255, 0.7); }
+    50% { opacity: 0.6; box-shadow: 0 0 6px 3px rgba(74, 158, 255, 0.3); }
+}
+
+/* VDL2 message animation */
+.vdl2-msg {
+    padding: 6px 8px;
+    border-bottom: 1px solid var(--border-color);
+    animation: vdl2FadeIn 0.3s ease;
+}
+.vdl2-msg:hover {
+    background: rgba(74, 158, 255, 0.05);
+}
+@keyframes vdl2FadeIn {
+    from { opacity: 0; transform: translateY(-3px); }
+    to { opacity: 1; transform: translateY(0); }
+}

templates/adsb_dashboard.html

@@ -92,8 +92,12 @@
                 <span class="strip-value" id="stripAcars">0</span>
                 <span class="strip-label">ACARS</span>
             </div>
+            <div class="strip-stat">
+                <span class="strip-value" id="stripVdl2">0</span>
+                <span class="strip-label">VDL2</span>
+            </div>
             <div class="strip-stat source-stat" title="Data source (Local or Agent name)">
-                <span class="strip-value" id="stripSource" style="font-size: 10px;">Local</span>
+                <span class="strip-value" id="stripSource">Local</span>
                 <span class="strip-label">SOURCE</span>
             </div>
             <div class="strip-stat signal-stat" title="Signal quality (messages/errors)">
@@ -106,17 +110,25 @@
             </div>
             <div class="strip-divider"></div>
             <button type="button" class="strip-btn" onclick="showSquawkInfo(null)" title="Squawk Code Reference">
-                📟 Squawk
+                <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><rect x="2" y="6" width="20" height="12" rx="2"/><line x1="6" y1="10" x2="6" y2="14"/><line x1="10" y1="10" x2="10" y2="14"/><line x1="14" y1="10" x2="14" y2="14"/><line x1="18" y1="10" x2="18" y2="14"/></svg>
+                Squawk
             </button>
             <button type="button" class="strip-btn" onclick="lookupSelectedFlight()" title="Lookup selected aircraft on FlightAware" id="flightLookupBtn" disabled>
-                🔗 Lookup
+                <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M10 13a5 5 0 0 0 7.54.54l3-3a5 5 0 0 0-7.07-7.07l-1.72 1.71"/><path d="M14 11a5 5 0 0 0-7.54-.54l-3 3a5 5 0 0 0 7.07 7.07l1.71-1.71"/></svg>
+                Lookup
             </button>
             <button type="button" class="strip-btn primary" onclick="generateReport()" title="Generate Session Report">
-                📊 Report
+                <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><line x1="18" y1="20" x2="18" y2="10"/><line x1="12" y1="20" x2="12" y2="4"/><line x1="6" y1="20" x2="6" y2="14"/></svg>
+                Report
             </button>
             <a class="strip-btn" href="/adsb/history" title="Open History Reporting">
-                📚 History
+                <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><circle cx="12" cy="12" r="10"/><polyline points="12 6 12 12 16 14"/></svg>
+                History
             </a>
+            <button type="button" class="strip-btn" onclick="toggleAntennaGuide()" title="1090 MHz Antenna Guide">
+                <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M2 12 L12 2 L22 12"/><line x1="12" y1="2" x2="12" y2="22"/><path d="M4.93 4.93 L12 12"/><path d="M19.07 4.93 L12 12"/></svg>
+                Antenna
+            </button>
             <div class="strip-divider"></div>
             <div class="strip-status">
                 <div class="status-dot inactive" id="trackingDot"></div>
@@ -176,6 +188,55 @@
             </button>
         </div>
 
+        <!-- VDL2 Panel (left of map, after ACARS) - Collapsible -->
+        <div class="vdl2-sidebar" id="vdl2Sidebar">
+            <div class="vdl2-sidebar-content" id="vdl2SidebarContent">
+                <div class="panel vdl2-panel">
+                    <div class="panel-header">
+                        <span>VDL2 MESSAGES</span>
+                        <div style="display: flex; align-items: center; gap: 8px;">
+                            <span id="vdl2Count" style="font-size: 10px; color: var(--accent-cyan);">0</span>
+                            <div class="panel-indicator" id="vdl2PanelIndicator"></div>
+                        </div>
+                    </div>
+                    <div id="vdl2PanelContent">
+                        <div class="vdl2-info" style="font-size: 9px; color: var(--text-muted); padding: 5px 8px; border-bottom: 1px solid var(--border-color);">
+                            <span style="color: var(--accent-yellow);">&#9888;</span> Requires separate SDR (VHF ~137 MHz)
+                        </div>
+                        <div class="vdl2-controls" style="padding: 8px; border-bottom: 1px solid var(--border-color);">
+                            <div style="display: flex; gap: 5px; margin-bottom: 5px;">
+                                <select id="vdl2DeviceSelect" style="flex: 1; font-size: 10px;">
+                                    <option value="0">SDR 0</option>
+                                    <option value="1">SDR 1</option>
+                                </select>
+                                <select id="vdl2RegionDashSelect" onchange="updateVdl2FreqCheckboxes()" style="flex: 1; font-size: 10px;">
+                                    <option value="na">N. America</option>
+                                    <option value="eu">Europe</option>
+                                    <option value="ap">Asia-Pac</option>
+                                </select>
+                            </div>
+                            <div id="vdl2FreqSelector" style="display: flex; flex-wrap: wrap; gap: 4px; margin-bottom: 8px; font-size: 9px;">
+                                <!-- Frequency checkboxes populated by JS -->
+                            </div>
+                            <button class="vdl2-btn" id="vdl2ToggleBtn" onclick="toggleVdl2()" style="width: 100%;">
+                                &#9654; START VDL2
+                            </button>
+                        </div>
+                        <div class="vdl2-messages" id="vdl2Messages">
+                            <div class="no-aircraft" style="padding: 20px; text-align: center;">
+                                <div style="font-size: 10px; color: var(--text-muted);">No VDL2 messages</div>
+                                <div style="font-size: 9px; color: var(--text-dim); margin-top: 5px;">Start VDL2 to receive digital datalink messages</div>
+                            </div>
+                        </div>
+                    </div>
+                </div>
+            </div>
+            <button class="vdl2-collapse-btn" id="vdl2CollapseBtn" onclick="toggleVdl2Sidebar()" title="Toggle VDL2 Panel">
+                <span id="vdl2CollapseIcon">&#9664;</span>
+                <span class="vdl2-collapse-label">VDL2</span>
+            </button>
+        </div>
+
         <!-- Main Display (Map or Radar Scope) -->
         <div class="main-display">
             <div class="display-container">
@@ -223,88 +284,6 @@
                     </div>
                 </div>
             </div>
-
-            <!-- Antenna Guide Panel -->
-            <div class="panel" id="antennaGuidePanel">
-                <div class="panel-header" style="cursor: pointer;" onclick="document.getElementById('antennaGuideContent').style.display = document.getElementById('antennaGuideContent').style.display === 'none' ? 'block' : 'none'; this.querySelector('.panel-toggle').textContent = document.getElementById('antennaGuideContent').style.display === 'none' ? '&#9654;' : '&#9660;';">
-                    <span>ANTENNA GUIDE</span>
-                    <span class="panel-toggle" style="font-size: 10px; color: var(--text-muted);">&#9654;</span>
-                </div>
-                <div id="antennaGuideContent" style="display: none; padding: 10px; font-size: 11px; color: var(--text-secondary); line-height: 1.5;">
-                    <p style="margin-bottom: 8px; color: var(--accent-cyan); font-weight: 600;">
-                        1090 MHz &mdash; stock SDR antenna can work but is not ideal
-                    </p>
-
-                    <div style="background: rgba(0,0,0,0.3); border: 1px solid var(--border-color); border-radius: 4px; padding: 8px; margin-bottom: 8px;">
-                        <strong style="color: var(--accent-cyan); font-size: 11px;">Stock Telescopic Antenna</strong>
-                        <ul style="margin: 4px 0 0 14px; padding: 0; font-size: 10px;">
-                            <li><strong style="color: var(--text-primary);">1090 MHz:</strong> Collapse to ~6.9 cm (quarter-wave). It works for nearby aircraft</li>
-                            <li><strong style="color: var(--text-primary);">Range:</strong> Expect ~50 NM (90 km) indoors, ~100 NM outdoors</li>
-                        </ul>
-                    </div>
-
-                    <div style="background: rgba(0,0,0,0.3); border: 1px solid var(--border-color); border-radius: 4px; padding: 8px; margin-bottom: 8px;">
-                        <strong style="color: #00ff88; font-size: 11px;">Recommended: 1090 MHz Collinear (~$10-20 DIY)</strong>
-                        <ul style="margin: 4px 0 0 14px; padding: 0; font-size: 10px;">
-                            <li><strong style="color: var(--text-primary);">Design:</strong> 8 coaxial collinear elements from RG-6 coax cable</li>
-                            <li><strong style="color: var(--text-primary);">Element length:</strong> ~6.9 cm segments soldered alternating center/shield</li>
-                            <li><strong style="color: var(--text-primary);">Gain:</strong> ~5&ndash;7 dBi omnidirectional, ideal for 360&deg; coverage</li>
-                            <li><strong style="color: var(--text-primary);">Range:</strong> 150&ndash;250+ NM depending on height and LOS</li>
-                        </ul>
-                    </div>
-
-                    <div style="background: rgba(0,0,0,0.3); border: 1px solid var(--border-color); border-radius: 4px; padding: 8px; margin-bottom: 8px;">
-                        <strong style="color: var(--accent-cyan); font-size: 11px;">Commercial Options</strong>
-                        <ul style="margin: 4px 0 0 14px; padding: 0; font-size: 10px;">
-                            <li><strong style="color: var(--text-primary);">FlightAware antenna:</strong> ~$35, 1090 MHz tuned, 66cm fiberglass whip</li>
-                            <li><strong style="color: var(--text-primary);">ADSBexchange whip:</strong> ~$40, similar performance</li>
-                            <li><strong style="color: var(--text-primary);">Jetvision A3:</strong> ~$50, high-gain 1090 MHz collinear</li>
-                        </ul>
-                    </div>
-
-                    <div style="background: rgba(0,0,0,0.3); border: 1px solid var(--border-color); border-radius: 4px; padding: 8px; margin-bottom: 8px;">
-                        <strong style="color: var(--accent-cyan); font-size: 11px;">Placement & LNA</strong>
-                        <ul style="margin: 4px 0 0 14px; padding: 0; font-size: 10px;">
-                            <li><strong style="color: var(--text-primary);">Location:</strong> OUTDOORS, as high as possible. Roof or mast mount</li>
-                            <li><strong style="color: var(--text-primary);">Height:</strong> Every 3m higher adds ~10 NM range (line-of-sight)</li>
-                            <li><strong style="color: var(--text-primary);">LNA:</strong> 1090 MHz filtered LNA at antenna feed (e.g. Uputronics, ~$30)</li>
-                            <li><strong style="color: var(--text-primary);">Filter:</strong> A 1090 MHz bandpass filter removes cell/FM interference</li>
-                            <li><strong style="color: var(--text-primary);">Coax:</strong> Keep short. At 1090 MHz, RG-58 loses ~10 dB per 10m</li>
-                            <li><strong style="color: var(--text-primary);">Bias-T:</strong> Enable Bias-T in controls above if LNA is powered via coax</li>
-                        </ul>
-                    </div>
-
-                    <div style="background: rgba(0,0,0,0.3); border: 1px solid var(--border-color); border-radius: 4px; padding: 8px;">
-                        <strong style="color: var(--accent-cyan); font-size: 11px;">Quick Reference</strong>
-                        <table style="width: 100%; margin-top: 4px; font-size: 10px; border-collapse: collapse;">
-                            <tr style="border-bottom: 1px solid var(--border-color);">
-                                <td style="padding: 2px 4px; color: var(--text-dim);">ADS-B frequency</td>
-                                <td style="padding: 2px 4px; color: var(--text-primary); text-align: right;">1090 MHz</td>
-                            </tr>
-                            <tr style="border-bottom: 1px solid var(--border-color);">
-                                <td style="padding: 2px 4px; color: var(--text-dim);">Quarter-wave length</td>
-                                <td style="padding: 2px 4px; color: var(--text-primary); text-align: right;">6.9 cm</td>
-                            </tr>
-                            <tr style="border-bottom: 1px solid var(--border-color);">
-                                <td style="padding: 2px 4px; color: var(--text-dim);">Modulation</td>
-                                <td style="padding: 2px 4px; color: var(--text-primary); text-align: right;">PPM (pulse)</td>
-                            </tr>
-                            <tr style="border-bottom: 1px solid var(--border-color);">
-                                <td style="padding: 2px 4px; color: var(--text-dim);">Polarization</td>
-                                <td style="padding: 2px 4px; color: var(--text-primary); text-align: right;">Vertical</td>
-                            </tr>
-                            <tr style="border-bottom: 1px solid var(--border-color);">
-                                <td style="padding: 2px 4px; color: var(--text-dim);">Bandwidth</td>
-                                <td style="padding: 2px 4px; color: var(--text-primary); text-align: right;">~2 MHz</td>
-                            </tr>
-                            <tr>
-                                <td style="padding: 2px 4px; color: var(--text-dim);">Typical range (outdoor)</td>
-                                <td style="padding: 2px 4px; color: var(--text-primary); text-align: right;">100&ndash;250 NM</td>
-                            </tr>
-                        </table>
-                    </div>
-                </div>
-            </div>
         </div>
 
         <!-- Controls Bar - Reorganized -->
@@ -4115,6 +4094,211 @@ sudo make install</code>
                 });
         });
 
+        // ============================================
+        // VDL2 DATALINK PANEL
+        // ============================================
+        let vdl2EventSource = null;
+        let isVdl2Running = false;
+        let vdl2MessageCount = 0;
+        let vdl2SidebarCollapsed = localStorage.getItem('vdl2SidebarCollapsed') !== 'false';
+        let vdl2Frequencies = {
+            'na': ['136975000', '136100000', '136650000', '136700000', '136800000'],
+            'eu': ['136975000', '136675000', '136725000', '136775000', '136825000'],
+            'ap': ['136975000', '136900000']
+        };
+        let vdl2FreqLabels = {
+            '136975000': '136.975', '136100000': '136.100', '136650000': '136.650',
+            '136700000': '136.700', '136800000': '136.800', '136675000': '136.675',
+            '136725000': '136.725', '136775000': '136.775', '136825000': '136.825',
+            '136900000': '136.900'
+        };
+
+        function toggleVdl2Sidebar() {
+            const sidebar = document.getElementById('vdl2Sidebar');
+            vdl2SidebarCollapsed = !vdl2SidebarCollapsed;
+            sidebar.classList.toggle('collapsed', vdl2SidebarCollapsed);
+            localStorage.setItem('vdl2SidebarCollapsed', vdl2SidebarCollapsed);
+        }
+
+        document.addEventListener('DOMContentLoaded', () => {
+            const sidebar = document.getElementById('vdl2Sidebar');
+            if (sidebar && vdl2SidebarCollapsed) {
+                sidebar.classList.add('collapsed');
+            }
+            updateVdl2FreqCheckboxes();
+        });
+
+        function updateVdl2FreqCheckboxes() {
+            const region = document.getElementById('vdl2RegionDashSelect').value;
+            const freqs = vdl2Frequencies[region] || vdl2Frequencies['na'];
+            const container = document.getElementById('vdl2FreqSelector');
+
+            const previouslyChecked = new Set();
+            container.querySelectorAll('input:checked').forEach(cb => previouslyChecked.add(cb.value));
+
+            container.innerHTML = freqs.map(freq => {
+                const checked = previouslyChecked.size === 0 || previouslyChecked.has(freq) ? 'checked' : '';
+                const label = vdl2FreqLabels[freq] || freq;
+                return `
+                    <label style="display: flex; align-items: center; gap: 3px; padding: 2px 6px; background: var(--bg-secondary); border-radius: 3px; cursor: pointer;">
+                        <input type="checkbox" class="vdl2-freq-cb" value="${freq}" ${checked} style="margin: 0; cursor: pointer;">
+                        <span>${label}</span>
+                    </label>
+                `;
+            }).join('');
+        }
+
+        function getVdl2RegionFreqs() {
+            const checkboxes = document.querySelectorAll('.vdl2-freq-cb:checked');
+            const selectedFreqs = Array.from(checkboxes).map(cb => cb.value);
+            if (selectedFreqs.length === 0) {
+                const region = document.getElementById('vdl2RegionDashSelect').value;
+                return vdl2Frequencies[region] || vdl2Frequencies['na'];
+            }
+            return selectedFreqs;
+        }
+
+        function toggleVdl2() {
+            if (isVdl2Running) {
+                stopVdl2();
+            } else {
+                startVdl2();
+            }
+        }
+
+        function startVdl2() {
+            const vdl2Select = document.getElementById('vdl2DeviceSelect');
+            const device = vdl2Select.value;
+            const sdr_type = vdl2Select.selectedOptions[0]?.dataset.sdrType || 'rtlsdr';
+            const frequencies = getVdl2RegionFreqs();
+
+            if (isTracking && device === '0') {
+                const useAnyway = confirm(
+                    'Warning: ADS-B tracking may be using SDR device 0.\n\n' +
+                    'VDL2 uses VHF frequencies (~137 MHz) while ADS-B uses 1090 MHz.\n' +
+                    'You need TWO separate SDR devices to receive both simultaneously.\n\n' +
+                    'Click OK to start VDL2 on device ' + device + ' anyway.'
+                );
+                if (!useAnyway) return;
+            }
+
+            fetch('/vdl2/start', {
+                method: 'POST',
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify({ device, frequencies, gain: '40', sdr_type })
+            })
+            .then(r => r.json())
+            .then(data => {
+                if (data.status === 'started') {
+                    isVdl2Running = true;
+                    vdl2MessageCount = 0;
+                    document.getElementById('vdl2ToggleBtn').innerHTML = '&#9632; STOP VDL2';
+                    document.getElementById('vdl2ToggleBtn').classList.add('active');
+                    document.getElementById('vdl2PanelIndicator').classList.add('active');
+                    startVdl2Stream();
+                } else {
+                    alert('VDL2 Error: ' + (data.message || 'Failed to start'));
+                }
+            })
+            .catch(err => alert('VDL2 Error: ' + err));
+        }
+
+        function stopVdl2() {
+            fetch('/vdl2/stop', { method: 'POST' })
+                .then(r => r.json())
+                .then(() => {
+                    isVdl2Running = false;
+                    document.getElementById('vdl2ToggleBtn').innerHTML = '&#9654; START VDL2';
+                    document.getElementById('vdl2ToggleBtn').classList.remove('active');
+                    document.getElementById('vdl2PanelIndicator').classList.remove('active');
+                    if (vdl2EventSource) {
+                        vdl2EventSource.close();
+                        vdl2EventSource = null;
+                    }
+                });
+        }
+
+        function startVdl2Stream() {
+            if (vdl2EventSource) vdl2EventSource.close();
+
+            vdl2EventSource = new EventSource('/vdl2/stream');
+            vdl2EventSource.onmessage = function(e) {
+                const data = JSON.parse(e.data);
+                if (data.type === 'vdl2') {
+                    vdl2MessageCount++;
+                    if (typeof stats !== 'undefined') stats.vdl2Messages = (stats.vdl2Messages || 0) + 1;
+                    document.getElementById('vdl2Count').textContent = vdl2MessageCount;
+                    document.getElementById('stripVdl2').textContent = vdl2MessageCount;
+                    addVdl2Message(data);
+                }
+            };
+
+            vdl2EventSource.onerror = function() {
+                console.error('VDL2 stream error');
+            };
+        }
+
+        function addVdl2Message(data) {
+            const container = document.getElementById('vdl2Messages');
+
+            const placeholder = container.querySelector('.no-aircraft');
+            if (placeholder) placeholder.remove();
+
+            const msg = document.createElement('div');
+            msg.className = 'vdl2-message-item';
+            msg.style.cssText = 'padding: 6px 8px; border-bottom: 1px solid var(--border-color); font-size: 10px;';
+
+            const station = data.station || '';
+            const avlc = data.avlc || {};
+            const src = avlc.src?.addr || '';
+            const dst = avlc.dst?.addr || '';
+            const acars = avlc.acars || {};
+            const flight = acars.flight || '';
+            const msgText = acars.msg_text || '';
+            const time = new Date().toLocaleTimeString();
+            const freq = data.freq ? (data.freq / 1000000).toFixed(3) : '';
+
+            msg.innerHTML = `
+                <div style="display: flex; justify-content: space-between; margin-bottom: 2px;">
+                    <span style="color: var(--accent-cyan); font-weight: bold;">${flight || src || 'VDL2'}</span>
+                    <span style="color: var(--text-muted);">${time}</span>
+                </div>
+                ${freq ? `<div style="color: var(--text-dim); font-size: 9px;">${freq} MHz</div>` : ''}
+                ${dst ? `<div style="color: var(--text-muted); font-size: 9px;">To: ${dst}</div>` : ''}
+                ${msgText ? `<div style="color: var(--text-primary); margin-top: 3px; word-break: break-word;">${msgText}</div>` : ''}
+            `;
+
+            container.insertBefore(msg, container.firstChild);
+
+            while (container.children.length > 50) {
+                container.removeChild(container.lastChild);
+            }
+        }
+
+        // Populate VDL2 device selector
+        document.addEventListener('DOMContentLoaded', () => {
+            fetch('/devices')
+                .then(r => r.json())
+                .then(devices => {
+                    const select = document.getElementById('vdl2DeviceSelect');
+                    select.innerHTML = '';
+                    if (devices.length === 0) {
+                        select.innerHTML = '<option value="0">No SDR detected</option>';
+                    } else {
+                        devices.forEach((d, i) => {
+                            const opt = document.createElement('option');
+                            opt.value = d.index || i;
+                            opt.dataset.sdrType = d.sdr_type || 'rtlsdr';
+                            opt.textContent = `SDR ${d.index || i}: ${d.name || d.type || 'SDR'}`;
+                            select.appendChild(opt);
+                        });
+                        if (devices.length > 1) {
+                            select.value = '1';
+                        }
+                    }
+                });
+        });
+
         // ============================================
         // SQUAWK CODE REFERENCE
         // ============================================
@@ -4174,6 +4358,18 @@ sudo make install</code>
         document.getElementById('squawkModal')?.addEventListener('click', (e) => {
             if (e.target.id === 'squawkModal') closeSquawkModal();
         });
+
+        // ============================================
+        // ANTENNA GUIDE
+        // ============================================
+        function toggleAntennaGuide() {
+            const modal = document.getElementById('antennaGuideModal');
+            modal.classList.toggle('active');
+        }
+
+        document.getElementById('antennaGuideModal')?.addEventListener('click', (e) => {
+            if (e.target.id === 'antennaGuideModal') toggleAntennaGuide();
+        });
     </script>
 
     <!-- Squawk Code Reference Modal -->
@@ -4227,6 +4423,72 @@ sudo make install</code>
         </div>
     </div>
 
+    <!-- Antenna Guide Modal -->
+    <div id="antennaGuideModal" class="antenna-guide-modal">
+        <div class="antenna-guide-modal-content">
+            <div class="antenna-guide-modal-header">
+                <span>ANTENNA GUIDE &mdash; 1090 MHz ADS-B</span>
+                <button class="antenna-guide-modal-close" onclick="toggleAntennaGuide()">&times;</button>
+            </div>
+            <div class="antenna-guide-modal-body">
+                <p style="margin-bottom: 10px; color: var(--accent-cyan, #00d4ff); font-weight: 600; font-size: 12px;">
+                    1090 MHz &mdash; stock SDR antenna can work but is not ideal
+                </p>
+
+                <div class="antenna-section">
+                    <strong style="color: var(--accent-cyan, #00d4ff);">Stock Telescopic Antenna</strong>
+                    <ul>
+                        <li><strong>1090 MHz:</strong> Collapse to ~6.9 cm (quarter-wave). It works for nearby aircraft</li>
+                        <li><strong>Range:</strong> Expect ~50 NM (90 km) indoors, ~100 NM outdoors</li>
+                    </ul>
+                </div>
+
+                <div class="antenna-section recommended">
+                    <strong style="color: #00ff88;">Recommended: 1090 MHz Collinear (~$10-20 DIY)</strong>
+                    <ul>
+                        <li><strong>Design:</strong> 8 coaxial collinear elements from RG-6 coax cable</li>
+                        <li><strong>Element length:</strong> ~6.9 cm segments soldered alternating center/shield</li>
+                        <li><strong>Gain:</strong> ~5&ndash;7 dBi omnidirectional, ideal for 360&deg; coverage</li>
+                        <li><strong>Range:</strong> 150&ndash;250+ NM depending on height and LOS</li>
+                    </ul>
+                </div>
+
+                <div class="antenna-section">
+                    <strong style="color: var(--accent-cyan, #00d4ff);">Commercial Options</strong>
+                    <ul>
+                        <li><strong>FlightAware antenna:</strong> ~$35, 1090 MHz tuned, 66cm fiberglass whip</li>
+                        <li><strong>ADSBexchange whip:</strong> ~$40, similar performance</li>
+                        <li><strong>Jetvision A3:</strong> ~$50, high-gain 1090 MHz collinear</li>
+                    </ul>
+                </div>
+
+                <div class="antenna-section">
+                    <strong style="color: var(--accent-cyan, #00d4ff);">Placement &amp; LNA</strong>
+                    <ul>
+                        <li><strong>Location:</strong> OUTDOORS, as high as possible. Roof or mast mount</li>
+                        <li><strong>Height:</strong> Every 3m higher adds ~10 NM range (line-of-sight)</li>
+                        <li><strong>LNA:</strong> 1090 MHz filtered LNA at antenna feed (e.g. Uputronics, ~$30)</li>
+                        <li><strong>Filter:</strong> A 1090 MHz bandpass filter removes cell/FM interference</li>
+                        <li><strong>Coax:</strong> Keep short. At 1090 MHz, RG-58 loses ~10 dB per 10m</li>
+                        <li><strong>Bias-T:</strong> Enable Bias-T in controls above if LNA is powered via coax</li>
+                    </ul>
+                </div>
+
+                <div class="antenna-section">
+                    <strong style="color: var(--accent-cyan, #00d4ff);">Quick Reference</strong>
+                    <table class="antenna-ref-table">
+                        <tr><td>ADS-B frequency</td><td>1090 MHz</td></tr>
+                        <tr><td>Quarter-wave length</td><td>6.9 cm</td></tr>
+                        <tr><td>Modulation</td><td>PPM (pulse)</td></tr>
+                        <tr><td>Polarization</td><td>Vertical</td></tr>
+                        <tr><td>Bandwidth</td><td>~2 MHz</td></tr>
+                        <tr><td>Typical range (outdoor)</td><td>100&ndash;250 NM</td></tr>
+                    </table>
+                </div>
+            </div>
+        </div>
+    </div>
+
     <style>
         .squawk-clickable {
             cursor: pointer;
@@ -4374,6 +4636,108 @@ sudo make install</code>
             color: #000;
         }
 
+        /* Antenna Guide Modal */
+        .antenna-guide-modal {
+            display: none;
+            position: fixed;
+            top: 0;
+            left: 0;
+            width: 100%;
+            height: 100%;
+            background: rgba(0, 0, 0, 0.8);
+            z-index: 1000;
+            justify-content: center;
+            align-items: center;
+        }
+        .antenna-guide-modal.active {
+            display: flex;
+        }
+        .antenna-guide-modal-content {
+            background: var(--bg-secondary, #1a1a1a);
+            border: 1px solid var(--border-color, #333);
+            border-radius: 8px;
+            width: 90%;
+            max-width: 480px;
+            max-height: 80vh;
+            overflow: hidden;
+            display: flex;
+            flex-direction: column;
+        }
+        .antenna-guide-modal-header {
+            display: flex;
+            justify-content: space-between;
+            align-items: center;
+            padding: 12px 16px;
+            background: var(--bg-tertiary, #252525);
+            border-bottom: 1px solid var(--border-color, #333);
+            font-weight: 600;
+            font-size: 12px;
+            letter-spacing: 0.1em;
+            color: var(--accent-cyan, #00d4ff);
+        }
+        .antenna-guide-modal-close {
+            background: none;
+            border: none;
+            color: var(--text-secondary, #888);
+            font-size: 20px;
+            cursor: pointer;
+            padding: 0 4px;
+        }
+        .antenna-guide-modal-close:hover {
+            color: #fff;
+        }
+        .antenna-guide-modal-body {
+            padding: 16px;
+            overflow-y: auto;
+            font-size: 11px;
+            color: var(--text-secondary, #999);
+            line-height: 1.5;
+        }
+        .antenna-section {
+            background: rgba(0,0,0,0.3);
+            border: 1px solid var(--border-color, #333);
+            border-radius: 4px;
+            padding: 10px;
+            margin-bottom: 8px;
+        }
+        .antenna-section strong {
+            font-size: 11px;
+            display: block;
+            margin-bottom: 4px;
+        }
+        .antenna-section ul {
+            margin: 4px 0 0 14px;
+            padding: 0;
+            font-size: 10px;
+        }
+        .antenna-section ul li {
+            margin-bottom: 2px;
+        }
+        .antenna-section ul li strong {
+            display: inline;
+            color: var(--text-primary, #fff);
+            font-size: 10px;
+        }
+        .antenna-ref-table {
+            width: 100%;
+            margin-top: 6px;
+            font-size: 10px;
+            border-collapse: collapse;
+        }
+        .antenna-ref-table tr {
+            border-bottom: 1px solid var(--border-color, #333);
+        }
+        .antenna-ref-table td {
+            padding: 3px 4px;
+        }
+        .antenna-ref-table td:first-child {
+            color: var(--text-dim, #666);
+        }
+        .antenna-ref-table td:last-child {
+            color: var(--text-primary, #fff);
+            text-align: right;
+        }
+
         /* Watchlist Modal */
         .watchlist-modal {
             display: none;

templates/index.html

@@ -51,6 +51,7 @@
     <link rel="stylesheet" href="{{ url_for('static', filename='css/global-nav.css') }}">
     <link rel="stylesheet" href="{{ url_for('static', filename='css/index.css') }}">
     <link rel="stylesheet" href="{{ url_for('static', filename='css/modes/acars.css') }}">
+    <link rel="stylesheet" href="{{ url_for('static', filename='css/modes/vdl2.css') }}">
     <link rel="stylesheet" href="{{ url_for('static', filename='css/modes/aprs.css') }}">
     <link rel="stylesheet" href="{{ url_for('static', filename='css/modes/tscm.css') }}">
     <link rel="stylesheet" href="{{ url_for('static', filename='css/components/signal-cards.css') }}">
@@ -569,6 +570,10 @@
 
                 {% include 'partials/modes/bt_locate.html' %}
 
+                {% include 'partials/modes/acars.html' %}
+
+                {% include 'partials/modes/vdl2.html' %}
+
                 <button class="preset-btn" onclick="killAll()"
                     style="width: 100%; margin-top: 10px; border-color: #ff3366; color: #ff3366;">
                     Kill All Processes
@@ -3158,7 +3163,8 @@
         const validModes = new Set([
             'pager', 'sensor', 'rtlamr', 'aprs', 'listening',
             'spystations', 'meshtastic', 'wifi', 'bluetooth', 'bt_locate',
-            'tscm', 'satellite', 'sstv', 'weathersat', 'sstv_general', 'gps', 'websdr', 'subghz'
+            'tscm', 'satellite', 'sstv', 'weathersat', 'sstv_general', 'gps', 'websdr', 'subghz',
+            'acars', 'vdl2'
         ]);
 
         function getModeFromQuery() {
@@ -3617,7 +3623,7 @@
                 'wifi': 'wireless', 'bluetooth': 'wireless', 'bt_locate': 'wireless',
                 'tscm': 'security',
                 'rtlamr': 'sdr', 'ais': 'sdr', 'spystations': 'sdr',
-                'meshtastic': 'sdr',
+                'meshtastic': 'sdr', 'acars': 'sdr', 'vdl2': 'sdr',
                 'satellite': 'space', 'sstv': 'space', 'weathersat': 'space', 'sstv_general': 'space', 'gps': 'space',
                 'subghz': 'sdr'
             };
@@ -3722,6 +3728,8 @@
             document.getElementById('dmrMode')?.classList.toggle('active', mode === 'dmr');
             document.getElementById('websdrMode')?.classList.toggle('active', mode === 'websdr');
             document.getElementById('subghzMode')?.classList.toggle('active', mode === 'subghz');
+            document.getElementById('acarsMode')?.classList.toggle('active', mode === 'acars');
+            document.getElementById('vdl2Mode')?.classList.toggle('active', mode === 'vdl2');
             const pagerStats = document.getElementById('pagerStats');
             const sensorStats = document.getElementById('sensorStats');
             const satelliteStats = document.getElementById('satelliteStats');
@@ -3762,7 +3770,9 @@
                 'meshtastic': 'MESHTASTIC',
                 'dmr': 'DIGITAL VOICE',
                 'websdr': 'WEBSDR',
-                'subghz': 'SUBGHZ'
+                'subghz': 'SUBGHZ',
+                'acars': 'ACARS',
+                'vdl2': 'VDL2'
             };
             const activeModeIndicator = document.getElementById('activeModeIndicator');
             if (activeModeIndicator) activeModeIndicator.innerHTML = '<span class="pulse-dot"></span>' + (modeNames[mode] || mode.toUpperCase());
@@ -3836,7 +3846,9 @@
                 'meshtastic': 'Meshtastic Mesh Monitor',
                 'dmr': 'Digital Voice Decoder',
                 'websdr': 'HF/Shortwave WebSDR',
-                'subghz': 'SubGHz Transceiver'
+                'subghz': 'SubGHz Transceiver',
+                'acars': 'ACARS Aircraft Messaging',
+                'vdl2': 'VDL2 Aircraft Datalink'
             };
             const outputTitle = document.getElementById('outputTitle');
             if (outputTitle) outputTitle.textContent = titles[mode] || 'Signal Monitor';
@@ -3854,7 +3866,7 @@
             const reconBtn = document.getElementById('reconBtn');
             const intelBtn = document.querySelector('[onclick="exportDeviceDB()"]');
             const reconPanel = document.getElementById('reconPanel');
-            if (mode === 'satellite' || mode === 'sstv' || mode === 'weathersat' || mode === 'sstv_general' || mode === 'gps' || mode === 'listening' || mode === 'aprs' || mode === 'tscm' || mode === 'spystations' || mode === 'meshtastic' || mode === 'dmr' || mode === 'websdr' || mode === 'subghz') {
+            if (mode === 'satellite' || mode === 'sstv' || mode === 'weathersat' || mode === 'sstv_general' || mode === 'gps' || mode === 'listening' || mode === 'aprs' || mode === 'tscm' || mode === 'spystations' || mode === 'meshtastic' || mode === 'dmr' || mode === 'websdr' || mode === 'subghz' || mode === 'acars' || mode === 'vdl2') {
                 if (reconPanel) reconPanel.style.display = 'none';
                 if (reconBtn) reconBtn.style.display = 'none';
                 if (intelBtn) intelBtn.style.display = 'none';
@@ -3869,12 +3881,12 @@
 
             // Show agent selector for modes that support remote agents
             const agentSection = document.getElementById('agentSection');
-            const agentModes = ['pager', 'sensor', 'rtlamr', 'listening', 'aprs', 'wifi', 'bluetooth', 'aircraft', 'tscm', 'ais', 'acars', 'dsc'];
+            const agentModes = ['pager', 'sensor', 'rtlamr', 'listening', 'aprs', 'wifi', 'bluetooth', 'aircraft', 'tscm', 'ais', 'acars', 'vdl2', 'dsc'];
             if (agentSection) agentSection.style.display = agentModes.includes(mode) ? 'block' : 'none';
 
             // Show RTL-SDR device section for modes that use it
             const rtlDeviceSection = document.getElementById('rtlDeviceSection');
-            if (rtlDeviceSection) rtlDeviceSection.style.display = (mode === 'pager' || mode === 'sensor' || mode === 'rtlamr' || mode === 'listening' || mode === 'aprs' || mode === 'sstv' || mode === 'weathersat' || mode === 'sstv_general' || mode === 'dmr') ? 'block' : 'none';
+            if (rtlDeviceSection) rtlDeviceSection.style.display = (mode === 'pager' || mode === 'sensor' || mode === 'rtlamr' || mode === 'listening' || mode === 'aprs' || mode === 'sstv' || mode === 'weathersat' || mode === 'sstv_general' || mode === 'dmr' || mode === 'acars' || mode === 'vdl2') ? 'block' : 'none';
 
             // Show waterfall panel if running in listening mode
             const waterfallPanel = document.getElementById('waterfallPanel');

templates/partials/modes/acars.html

@@ -0,0 +1,208 @@
+<!-- ACARS AIRCRAFT MESSAGING MODE -->
+<div id="acarsMode" class="mode-content" style="display: none;">
+    <div class="section">
+        <h3>ACARS Messaging</h3>
+        <div class="info-text" style="margin-bottom: 15px;">
+            Decode ACARS (Aircraft Communications Addressing and Reporting System) messages on VHF frequencies (~129-131 MHz). Captures flight data, weather reports, position updates, and operational messages from aircraft.
+        </div>
+    </div>
+
+    <div class="section">
+        <h3>Region &amp; Frequencies</h3>
+        <div class="form-group">
+            <label>Region</label>
+            <select id="acarsRegionSelect" onchange="updateAcarsMainFreqs()" style="width: 100%;">
+                <option value="na">North America</option>
+                <option value="eu">Europe</option>
+                <option value="ap">Asia-Pacific</option>
+            </select>
+        </div>
+        <div id="acarsMainFreqSelector" style="display: flex; flex-wrap: wrap; gap: 4px; margin-bottom: 10px; font-size: 11px;">
+            <!-- Populated by JS -->
+        </div>
+        <div class="form-group">
+            <label>Gain (dB, 0 = auto)</label>
+            <input type="number" id="acarsGainInput" value="40" min="0" max="50" placeholder="0-50">
+        </div>
+    </div>
+
+    <div class="section">
+        <h3>Status</h3>
+        <div id="acarsStatusDisplay" class="info-text">
+            <p>Status: <span id="acarsStatusText" style="color: var(--accent-yellow);">Standby</span></p>
+            <p>Messages: <span id="acarsMessageCount">0</span></p>
+        </div>
+    </div>
+
+    <!-- Antenna Guide -->
+    <div class="section">
+        <h3>Antenna Guide</h3>
+        <div style="font-size: 11px; color: var(--text-dim); line-height: 1.5;">
+            <p style="margin-bottom: 8px; color: var(--accent-cyan); font-weight: 600;">
+                VHF Airband (~130 MHz) &mdash; stock SDR antenna may work at close range
+            </p>
+
+            <div style="background: var(--bg-primary); border: 1px solid var(--border-color); border-radius: 4px; padding: 10px; margin-bottom: 10px;">
+                <strong style="color: var(--accent-cyan); font-size: 12px;">Simple Dipole</strong>
+                <ul style="margin: 6px 0 0 14px; padding: 0;">
+                    <li><strong style="color: var(--text-primary);">Element length:</strong> ~57 cm each (quarter-wave at 130 MHz)</li>
+                    <li><strong style="color: var(--text-primary);">Material:</strong> Wire, coat hanger, or copper rod</li>
+                    <li><strong style="color: var(--text-primary);">Orientation:</strong> Vertical (airband is vertically polarized)</li>
+                    <li><strong style="color: var(--text-primary);">Placement:</strong> Outdoors, as high as possible with clear sky view</li>
+                </ul>
+            </div>
+
+            <div style="background: var(--bg-primary); border: 1px solid var(--border-color); border-radius: 4px; padding: 10px;">
+                <strong style="color: var(--accent-cyan); font-size: 12px;">Quick Reference</strong>
+                <table style="width: 100%; margin-top: 6px; font-size: 10px; border-collapse: collapse;">
+                    <tr style="border-bottom: 1px solid var(--border-color);">
+                        <td style="padding: 3px 4px; color: var(--text-dim);">Primary (worldwide)</td>
+                        <td style="padding: 3px 4px; color: var(--text-primary); text-align: right;">131.550 MHz</td>
+                    </tr>
+                    <tr style="border-bottom: 1px solid var(--border-color);">
+                        <td style="padding: 3px 4px; color: var(--text-dim);">Quarter-wave length</td>
+                        <td style="padding: 3px 4px; color: var(--text-primary); text-align: right;">57 cm</td>
+                    </tr>
+                    <tr style="border-bottom: 1px solid var(--border-color);">
+                        <td style="padding: 3px 4px; color: var(--text-dim);">Modulation</td>
+                        <td style="padding: 3px 4px; color: var(--text-primary); text-align: right;">AM MSK 2400 baud</td>
+                    </tr>
+                    <tr>
+                        <td style="padding: 3px 4px; color: var(--text-dim);">Polarization</td>
+                        <td style="padding: 3px 4px; color: var(--text-primary); text-align: right;">Vertical</td>
+                    </tr>
+                </table>
+            </div>
+        </div>
+    </div>
+
+    <button class="run-btn" id="startAcarsBtn" onclick="startAcarsMode()">
+        Start ACARS
+    </button>
+    <button class="stop-btn" id="stopAcarsBtn" onclick="stopAcarsMode()" style="display: none;">
+        Stop ACARS
+    </button>
+</div>
+
+<script>
+    let acarsMainEventSource = null;
+    let acarsMainMsgCount = 0;
+
+    const acarsMainFrequencies = {
+        'na': ['129.125', '130.025', '130.450', '131.550'],
+        'eu': ['131.525', '131.725', '131.550'],
+        'ap': ['131.550', '131.450']
+    };
+
+    function updateAcarsMainFreqs() {
+        const region = document.getElementById('acarsRegionSelect').value;
+        const freqs = acarsMainFrequencies[region] || acarsMainFrequencies['na'];
+        const container = document.getElementById('acarsMainFreqSelector');
+
+        const previouslyChecked = new Set();
+        container.querySelectorAll('input:checked').forEach(cb => previouslyChecked.add(cb.value));
+
+        container.innerHTML = freqs.map(freq => {
+            const checked = previouslyChecked.size === 0 || previouslyChecked.has(freq) ? 'checked' : '';
+            return `
+                <label style="display: flex; align-items: center; gap: 3px; padding: 2px 6px; background: var(--bg-secondary); border-radius: 3px; cursor: pointer;">
+                    <input type="checkbox" class="acars-main-freq-cb" value="${freq}" ${checked} style="margin: 0; cursor: pointer;">
+                    <span>${freq}</span>
+                </label>
+            `;
+        }).join('');
+    }
+
+    function getAcarsMainSelectedFreqs() {
+        const checkboxes = document.querySelectorAll('.acars-main-freq-cb:checked');
+        const selected = Array.from(checkboxes).map(cb => cb.value);
+        if (selected.length === 0) {
+            const region = document.getElementById('acarsRegionSelect').value;
+            return acarsMainFrequencies[region] || acarsMainFrequencies['na'];
+        }
+        return selected;
+    }
+
+    function startAcarsMode() {
+        const gain = document.getElementById('acarsGainInput').value || '40';
+        const device = document.getElementById('deviceSelect')?.value || '0';
+        const frequencies = getAcarsMainSelectedFreqs();
+
+        fetch('/acars/start', {
+            method: 'POST',
+            headers: { 'Content-Type': 'application/json' },
+            body: JSON.stringify({ device, gain, frequencies })
+        })
+        .then(r => r.json())
+        .then(data => {
+            if (data.status === 'started') {
+                document.getElementById('startAcarsBtn').style.display = 'none';
+                document.getElementById('stopAcarsBtn').style.display = 'block';
+                document.getElementById('acarsStatusText').textContent = 'Listening';
+                document.getElementById('acarsStatusText').style.color = 'var(--accent-green)';
+                acarsMainMsgCount = 0;
+                startAcarsMainSSE();
+            } else {
+                alert(data.message || 'Failed to start ACARS');
+            }
+        })
+        .catch(err => alert('Error: ' + err.message));
+    }
+
+    function stopAcarsMode() {
+        fetch('/acars/stop', { method: 'POST' })
+        .then(r => r.json())
+        .then(() => {
+            document.getElementById('startAcarsBtn').style.display = 'block';
+            document.getElementById('stopAcarsBtn').style.display = 'none';
+            document.getElementById('acarsStatusText').textContent = 'Standby';
+            document.getElementById('acarsStatusText').style.color = 'var(--accent-yellow)';
+            if (acarsMainEventSource) {
+                acarsMainEventSource.close();
+                acarsMainEventSource = null;
+            }
+        });
+    }
+
+    function startAcarsMainSSE() {
+        if (acarsMainEventSource) acarsMainEventSource.close();
+
+        acarsMainEventSource = new EventSource('/acars/stream');
+        acarsMainEventSource.onmessage = function(e) {
+            try {
+                const data = JSON.parse(e.data);
+                if (data.type === 'acars') {
+                    acarsMainMsgCount++;
+                    document.getElementById('acarsMessageCount').textContent = acarsMainMsgCount;
+                }
+            } catch (err) {}
+        };
+
+        acarsMainEventSource.onerror = function() {
+            setTimeout(() => {
+                if (document.getElementById('stopAcarsBtn').style.display === 'block') {
+                    startAcarsMainSSE();
+                }
+            }, 2000);
+        };
+    }
+
+    // Check initial status
+    fetch('/acars/status')
+    .then(r => r.json())
+    .then(data => {
+        if (data.running) {
+            document.getElementById('startAcarsBtn').style.display = 'none';
+            document.getElementById('stopAcarsBtn').style.display = 'block';
+            document.getElementById('acarsStatusText').textContent = 'Listening';
+            document.getElementById('acarsStatusText').style.color = 'var(--accent-green)';
+            document.getElementById('acarsMessageCount').textContent = data.message_count || 0;
+            acarsMainMsgCount = data.message_count || 0;
+            startAcarsMainSSE();
+        }
+    })
+    .catch(() => {});
+
+    // Initialize frequency checkboxes
+    document.addEventListener('DOMContentLoaded', () => updateAcarsMainFreqs());
+</script>

templates/partials/modes/vdl2.html

@@ -0,0 +1,228 @@
+<!-- VDL2 AIRCRAFT DATALINK MODE -->
+<div id="vdl2Mode" class="mode-content" style="display: none;">
+    <div class="section">
+        <h3>VDL2 Datalink</h3>
+        <div class="info-text" style="margin-bottom: 15px;">
+            Decode VDL Mode 2 (VHF Digital Link) messages on ~136 MHz. VDL2 is the digital successor to ACARS, using D8PSK modulation for higher throughput aircraft datalink communications.
+        </div>
+    </div>
+
+    <div class="section">
+        <h3>Region &amp; Frequencies</h3>
+        <div class="form-group">
+            <label>Region</label>
+            <select id="vdl2RegionSelect" onchange="updateVdl2MainFreqs()" style="width: 100%;">
+                <option value="na">North America</option>
+                <option value="eu">Europe</option>
+                <option value="ap">Asia-Pacific</option>
+            </select>
+        </div>
+        <div id="vdl2MainFreqSelector" style="display: flex; flex-wrap: wrap; gap: 4px; margin-bottom: 10px; font-size: 11px;">
+            <!-- Populated by JS -->
+        </div>
+        <div class="form-group">
+            <label>Gain (dB, 0 = auto)</label>
+            <input type="number" id="vdl2GainInput" value="40" min="0" max="50" placeholder="0-50">
+        </div>
+    </div>
+
+    <div class="section">
+        <h3>Status</h3>
+        <div id="vdl2StatusDisplay" class="info-text">
+            <p>Status: <span id="vdl2StatusText" style="color: var(--accent-yellow);">Standby</span></p>
+            <p>Messages: <span id="vdl2MessageCount">0</span></p>
+        </div>
+    </div>
+
+    <!-- Antenna Guide -->
+    <div class="section">
+        <h3>Antenna Guide</h3>
+        <div style="font-size: 11px; color: var(--text-dim); line-height: 1.5;">
+            <p style="margin-bottom: 8px; color: var(--accent-cyan); font-weight: 600;">
+                VHF Airband (~137 MHz) &mdash; stock SDR antenna may work at close range
+            </p>
+
+            <div style="background: var(--bg-primary); border: 1px solid var(--border-color); border-radius: 4px; padding: 10px; margin-bottom: 10px;">
+                <strong style="color: var(--accent-cyan); font-size: 12px;">Simple Dipole</strong>
+                <ul style="margin: 6px 0 0 14px; padding: 0;">
+                    <li><strong style="color: var(--text-primary);">Element length:</strong> ~55 cm each (quarter-wave at 137 MHz)</li>
+                    <li><strong style="color: var(--text-primary);">Material:</strong> Wire, coat hanger, or copper rod</li>
+                    <li><strong style="color: var(--text-primary);">Orientation:</strong> Vertical (airband is vertically polarized)</li>
+                    <li><strong style="color: var(--text-primary);">Placement:</strong> Outdoors, as high as possible with clear sky view</li>
+                </ul>
+            </div>
+
+            <div style="background: var(--bg-primary); border: 1px solid var(--border-color); border-radius: 4px; padding: 10px;">
+                <strong style="color: var(--accent-cyan); font-size: 12px;">Quick Reference</strong>
+                <table style="width: 100%; margin-top: 6px; font-size: 10px; border-collapse: collapse;">
+                    <tr style="border-bottom: 1px solid var(--border-color);">
+                        <td style="padding: 3px 4px; color: var(--text-dim);">Primary (worldwide)</td>
+                        <td style="padding: 3px 4px; color: var(--text-primary); text-align: right;">136.975 MHz</td>
+                    </tr>
+                    <tr style="border-bottom: 1px solid var(--border-color);">
+                        <td style="padding: 3px 4px; color: var(--text-dim);">Quarter-wave length</td>
+                        <td style="padding: 3px 4px; color: var(--text-primary); text-align: right;">55 cm</td>
+                    </tr>
+                    <tr style="border-bottom: 1px solid var(--border-color);">
+                        <td style="padding: 3px 4px; color: var(--text-dim);">Modulation</td>
+                        <td style="padding: 3px 4px; color: var(--text-primary); text-align: right;">D8PSK 31.5 kbps</td>
+                    </tr>
+                    <tr style="border-bottom: 1px solid var(--border-color);">
+                        <td style="padding: 3px 4px; color: var(--text-dim);">Bandwidth</td>
+                        <td style="padding: 3px 4px; color: var(--text-primary); text-align: right;">25 kHz</td>
+                    </tr>
+                    <tr>
+                        <td style="padding: 3px 4px; color: var(--text-dim);">Polarization</td>
+                        <td style="padding: 3px 4px; color: var(--text-primary); text-align: right;">Vertical</td>
+                    </tr>
+                </table>
+            </div>
+        </div>
+    </div>
+
+    <button class="run-btn" id="startVdl2Btn" onclick="startVdl2Mode()">
+        Start VDL2
+    </button>
+    <button class="stop-btn" id="stopVdl2Btn" onclick="stopVdl2Mode()" style="display: none;">
+        Stop VDL2
+    </button>
+</div>
+
+<script>
+    let vdl2MainEventSource = null;
+    let vdl2MainMsgCount = 0;
+
+    // VDL2 frequencies in Hz (as required by dumpvdl2)
+    const vdl2MainFrequencies = {
+        'na': ['136975000', '136100000', '136650000', '136700000', '136800000'],
+        'eu': ['136975000', '136675000', '136725000', '136775000', '136825000'],
+        'ap': ['136975000', '136900000']
+    };
+
+    // Display-friendly MHz labels
+    const vdl2FreqLabels = {
+        '136975000': '136.975',
+        '136100000': '136.100',
+        '136650000': '136.650',
+        '136700000': '136.700',
+        '136800000': '136.800',
+        '136675000': '136.675',
+        '136725000': '136.725',
+        '136775000': '136.775',
+        '136825000': '136.825',
+        '136900000': '136.900'
+    };
+
+    function updateVdl2MainFreqs() {
+        const region = document.getElementById('vdl2RegionSelect').value;
+        const freqs = vdl2MainFrequencies[region] || vdl2MainFrequencies['na'];
+        const container = document.getElementById('vdl2MainFreqSelector');
+
+        const previouslyChecked = new Set();
+        container.querySelectorAll('input:checked').forEach(cb => previouslyChecked.add(cb.value));
+
+        container.innerHTML = freqs.map(freq => {
+            const checked = previouslyChecked.size === 0 || previouslyChecked.has(freq) ? 'checked' : '';
+            const label = vdl2FreqLabels[freq] || freq;
+            return `
+                <label style="display: flex; align-items: center; gap: 3px; padding: 2px 6px; background: var(--bg-secondary); border-radius: 3px; cursor: pointer;">
+                    <input type="checkbox" class="vdl2-main-freq-cb" value="${freq}" ${checked} style="margin: 0; cursor: pointer;">
+                    <span>${label}</span>
+                </label>
+            `;
+        }).join('');
+    }
+
+    function getVdl2MainSelectedFreqs() {
+        const checkboxes = document.querySelectorAll('.vdl2-main-freq-cb:checked');
+        const selected = Array.from(checkboxes).map(cb => cb.value);
+        if (selected.length === 0) {
+            const region = document.getElementById('vdl2RegionSelect').value;
+            return vdl2MainFrequencies[region] || vdl2MainFrequencies['na'];
+        }
+        return selected;
+    }
+
+    function startVdl2Mode() {
+        const gain = document.getElementById('vdl2GainInput').value || '40';
+        const device = document.getElementById('deviceSelect')?.value || '0';
+        const frequencies = getVdl2MainSelectedFreqs();
+
+        fetch('/vdl2/start', {
+            method: 'POST',
+            headers: { 'Content-Type': 'application/json' },
+            body: JSON.stringify({ device, gain, frequencies })
+        })
+        .then(r => r.json())
+        .then(data => {
+            if (data.status === 'started') {
+                document.getElementById('startVdl2Btn').style.display = 'none';
+                document.getElementById('stopVdl2Btn').style.display = 'block';
+                document.getElementById('vdl2StatusText').textContent = 'Listening';
+                document.getElementById('vdl2StatusText').style.color = 'var(--accent-green)';
+                vdl2MainMsgCount = 0;
+                startVdl2MainSSE();
+            } else {
+                alert(data.message || 'Failed to start VDL2');
+            }
+        })
+        .catch(err => alert('Error: ' + err.message));
+    }
+
+    function stopVdl2Mode() {
+        fetch('/vdl2/stop', { method: 'POST' })
+        .then(r => r.json())
+        .then(() => {
+            document.getElementById('startVdl2Btn').style.display = 'block';
+            document.getElementById('stopVdl2Btn').style.display = 'none';
+            document.getElementById('vdl2StatusText').textContent = 'Standby';
+            document.getElementById('vdl2StatusText').style.color = 'var(--accent-yellow)';
+            if (vdl2MainEventSource) {
+                vdl2MainEventSource.close();
+                vdl2MainEventSource = null;
+            }
+        });
+    }
+
+    function startVdl2MainSSE() {
+        if (vdl2MainEventSource) vdl2MainEventSource.close();
+
+        vdl2MainEventSource = new EventSource('/vdl2/stream');
+        vdl2MainEventSource.onmessage = function(e) {
+            try {
+                const data = JSON.parse(e.data);
+                if (data.type === 'vdl2') {
+                    vdl2MainMsgCount++;
+                    document.getElementById('vdl2MessageCount').textContent = vdl2MainMsgCount;
+                }
+            } catch (err) {}
+        };
+
+        vdl2MainEventSource.onerror = function() {
+            setTimeout(() => {
+                if (document.getElementById('stopVdl2Btn').style.display === 'block') {
+                    startVdl2MainSSE();
+                }
+            }, 2000);
+        };
+    }
+
+    // Check initial status
+    fetch('/vdl2/status')
+    .then(r => r.json())
+    .then(data => {
+        if (data.running) {
+            document.getElementById('startVdl2Btn').style.display = 'none';
+            document.getElementById('stopVdl2Btn').style.display = 'block';
+            document.getElementById('vdl2StatusText').textContent = 'Listening';
+            document.getElementById('vdl2StatusText').style.color = 'var(--accent-green)';
+            document.getElementById('vdl2MessageCount').textContent = data.message_count || 0;
+            vdl2MainMsgCount = data.message_count || 0;
+            startVdl2MainSSE();
+        }
+    })
+    .catch(() => {});
+
+    // Initialize frequency checkboxes
+    document.addEventListener('DOMContentLoaded', () => updateVdl2MainFreqs());
+</script>

templates/partials/nav.html

@@ -67,6 +67,8 @@
             {{ mode_item('rtlamr', 'Meters', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M22 12h-4l-3 9L9 3l-3 9H2"/></svg>') }}
             {{ mode_item('adsb', 'Aircraft', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M21 16v-2l-8-5V3.5a1.5 1.5 0 0 0-3 0V9l-8 5v2l8-2.5V19l-2 1.5V22l3.5-1 3.5 1v-1.5L13 19v-5.5l8 2.5z"/></svg>', '/adsb/dashboard') }}
             {{ mode_item('ais', 'Vessels', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M3 18l2 2h14l2-2"/><path d="M5 18v-4a2 2 0 0 1 2-2h10a2 2 0 0 1 2 2v4"/><path d="M12 12V6"/><path d="M12 6l4 3"/></svg>', '/ais/dashboard') }}
+            {{ mode_item('acars', 'ACARS', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M21 16v-2l-8-5V3.5a1.5 1.5 0 0 0-3 0V9l-8 5v2l8-2.5V19l-2 1.5V22l3.5-1 3.5 1v-1.5L13 19v-5.5l8 2.5z"/><line x1="4" y1="4" x2="8" y2="8"/><line x1="20" y1="4" x2="16" y2="8"/></svg>') }}
+            {{ mode_item('vdl2', 'VDL2', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M21 16v-2l-8-5V3.5a1.5 1.5 0 0 0-3 0V9l-8 5v2l8-2.5V19l-2 1.5V22l3.5-1 3.5 1v-1.5L13 19v-5.5l8 2.5z"/><path d="M2 2l4 4M22 2l-4 4M12 12v0"/></svg>') }}
             {{ mode_item('aprs', 'APRS', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M20 10c0 6-8 12-8 12s-8-6-8-12a8 8 0 0 1 16 0Z"/><circle cx="12" cy="10" r="3"/></svg>') }}
             {{ mode_item('listening', 'Listening Post', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><rect x="3" y="3" width="18" height="18" rx="2"/><path d="M3 9h18"/><path d="M9 21V9"/></svg>') }}
             {{ mode_item('spystations', 'Spy Stations', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M4.9 19.1C1 15.2 1 8.8 4.9 4.9"/><path d="M7.8 16.2c-2.3-2.3-2.3-6.1 0-8.5"/><circle cx="12" cy="12" r="2"/><path d="M16.2 7.8c2.3 2.3 2.3 6.1 0 8.5"/><path d="M19.1 4.9C23 8.8 23 15.1 19.1 19"/></svg>') }}
@@ -178,6 +180,8 @@
     {{ mobile_item('rtlamr', 'Meters', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M22 12h-4l-3 9L9 3l-3 9H2"/></svg>') }}
     {{ mobile_item('adsb', 'Aircraft', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M21 16v-2l-8-5V3.5a1.5 1.5 0 0 0-3 0V9l-8 5v2l8-2.5V19l-2 1.5V22l3.5-1 3.5 1v-1.5L13 19v-5.5l8 2.5z"/></svg>', '/adsb/dashboard') }}
     {{ mobile_item('ais', 'Vessels', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M3 18l2 2h14l2-2"/><path d="M5 18v-4a2 2 0 0 1 2-2h10a2 2 0 0 1 2 2v4"/><path d="M12 12V6"/><path d="M12 6l4 3"/></svg>', '/ais/dashboard') }}
+    {{ mobile_item('acars', 'ACARS', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M21 16v-2l-8-5V3.5a1.5 1.5 0 0 0-3 0V9l-8 5v2l8-2.5V19l-2 1.5V22l3.5-1 3.5 1v-1.5L13 19v-5.5l8 2.5z"/></svg>') }}
+    {{ mobile_item('vdl2', 'VDL2', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M21 16v-2l-8-5V3.5a1.5 1.5 0 0 0-3 0V9l-8 5v2l8-2.5V19l-2 1.5V22l3.5-1 3.5 1v-1.5L13 19v-5.5l8 2.5z"/></svg>') }}
     {{ mobile_item('aprs', 'APRS', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M20 10c0 6-8 12-8 12s-8-6-8-12a8 8 0 0 1 16 0Z"/><circle cx="12" cy="10" r="3"/></svg>') }}
     {{ mobile_item('wifi', 'WiFi', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M5 12.55a11 11 0 0 1 14.08 0"/><path d="M8.53 16.11a6 6 0 0 1 6.95 0"/><circle cx="12" cy="20" r="1" fill="currentColor"/></svg>') }}
     {{ mobile_item('bluetooth', 'BT', '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><polyline points="6.5 6.5 17.5 17.5 12 22 12 2 17.5 6.5 6.5 17.5"/></svg>') }}