From 790f03716474c0654c770b7b460a014dea14ecc9 Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Fri, 14 Nov 2025 03:03:47 +0000
Subject: [PATCH] Add mode selection validation test
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Creates test_mode_selection.py to validate Python implementation against
VOACAP reference output for problematic frequencies (7.20 and 9.70 MHz).

Key findings:
- Night predictions (UTC 1.0): Perfect match (±0.1 dB error)
- Midday predictions (UTC 11.0): Catastrophic failure (+97 to +144 dB error)
- E-layer modes show +80 dB SNR when VOACAP shows -15 to -64 dB
- Reliability shows 77-81% when VOACAP shows 0% (modes should be rejected)

This confirms the mode selection problem described in the issue.
---
 test_mode_selection.py | 92 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 test_mode_selection.py

diff --git a/test_mode_selection.py b/test_mode_selection.py
new file mode 100644
index 0000000..066d551
--- /dev/null
+++ b/test_mode_selection.py
@@ -0,0 +1,92 @@
+#!/usr/bin/env python3
+"""Test mode selection for problematic frequencies"""
+import sys
+import numpy as np
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).parent))
+
+from src.dvoacap.path_geometry import GeoPoint
+from src.dvoacap.prediction_engine import PredictionEngine
+
+# Test case from SampleIO/voacapx.out
+# Tangier, Morocco -> Belgrade
+TX_LAT, TX_LON = 35.80, -5.90
+RX_LAT, RX_LON = 44.90, 20.50
+SSN = 100.0
+MONTH = 6
+TX_POWER = 500000  # 500 kW
+
+FREQUENCIES = [7.20, 9.70]  # Problematic frequencies
+UTC_HOURS = [1.0, 11.0]  # Night (working) vs Midday (broken)
+
+# Reference values from VOACAP
+REFERENCE = {
+    (7.20, 1.0): {'mode': '1F2', 'snr': 76, 'rel': 0.61},
+    (9.70, 1.0): {'mode': '1F2', 'snr': 79, 'rel': 0.70},
+    (7.20, 11.0): {'mode': '2E', 'snr': -64, 'rel': 0.00},
+    (9.70, 11.0): {'mode': '2E', 'snr': -15, 'rel': 0.00},
+}
+
+print("=" * 80)
+print("TESTING MODE SELECTION: 7.20 MHz and 9.70 MHz")
+print("=" * 80)
+
+for utc in UTC_HOURS:
+    print(f"\n{'=' * 80}")
+    print(f"UTC HOUR: {utc:.1f}")
+    print(f"{'=' * 80}\n")
+
+    # Setup engine
+    engine = PredictionEngine()
+    engine.params.ssn = SSN
+    engine.params.month = MONTH
+    engine.params.tx_power = TX_POWER
+    engine.params.tx_location = GeoPoint.from_degrees(TX_LAT, TX_LON)
+    engine.params.min_angle = np.deg2rad(0.1)
+
+    rx_location = GeoPoint.from_degrees(RX_LAT, RX_LON)
+    utc_fraction = utc / 24.0
+
+    # Run predictions for both frequencies
+    engine.predict(rx_location=rx_location, utc_time=utc_fraction, frequencies=FREQUENCIES)
+
+    for freq, pred in zip(FREQUENCIES, engine.predictions):
+        print(f"\n--- {freq:.2f} MHz @ {utc:.1f} UTC ---")
+
+        if pred:
+            mode_name = pred.get_mode_name(engine.path.dist)
+            snr = pred.signal.snr_db
+            rel = pred.signal.reliability
+
+            print(f"  Mode: {mode_name}")
+            print(f"  Hops: {pred.hop_count}")
+            print(f"  SNR: {snr:.1f} dB")
+            print(f"  Reliability: {rel*100:.1f}%")
+            print(f"  TX Elevation: {np.rad2deg(pred.tx_elevation):.1f}°")
+            print(f"  Virtual Height: {pred.virt_height:.1f} km")
+            print(f"  Total Loss: {pred.signal.total_loss_db:.1f} dB")
+
+            # Get reference
+            ref = REFERENCE.get((freq, utc), {'mode': '?', 'snr': 0, 'rel': 0})
+
+            print(f"\n  VOACAP Reference:")
+            print(f"    Mode: {ref['mode']}")
+            print(f"    SNR: {ref['snr']} dB")
+            print(f"    Reliability: {ref['rel']*100:.0f}%")
+
+            snr_error = snr - ref['snr']
+            rel_error = (rel - ref['rel']) * 100
+
+            print(f"\n  ERRORS:")
+            print(f"    SNR Error: {snr_error:+.1f} dB")
+            print(f"    Reliability Error: {rel_error:+.1f}%")
+
+            if abs(snr_error) > 10:
+                print(f"    ⚠️  SNR ERROR EXCEEDS ±10 dB THRESHOLD!")
+            if abs(rel_error) > 20:
+                print(f"    ⚠️  RELIABILITY ERROR EXCEEDS ±20% THRESHOLD!")
+        else:
+            print("  NO PREDICTION GENERATED")
+
+print("\n" + "=" * 80)