From 91c8cc9bc710e09c61ae104d14ccbf05972a9893 Mon Sep 17 00:00:00 2001
From: Graham McIntire <graham@mcintire.me>
Date: Wed, 15 Apr 2026 14:22:32 -0500
Subject: [PATCH] Add 144 MHz and 440 MHz bands (tropo only)
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Both bands share the physics of low microwave: humidity and refractivity
gradient build ducts the same way, and rain + gas absorption are
effectively zero at VHF/UHF. humidity_effect is :beneficial, rain_k /
rain_alpha are (0, 1), and o2_db_km / h2o_coeff are 0.

Range estimates reflect tropo reality: 2m ducts can reach 2500+ km
under exceptional conditions (e.g. documented Hawaii ↔ California
openings), 70cm a bit less. The seasonal base matches the low-microwave
summer-peak curve.

These configs do NOT capture sporadic-E, meteor scatter, or aurora —
those need ionospheric data (GIRO ionosondes, NOAA SWPC) we don't yet
ingest. The scoring on these bands is therefore "tropo-only" and will
underestimate openings driven by ionospheric modes.
---
 lib/microwaveprop/propagation/band_config.ex  | 64 +++++++++++++++++++
 .../propagation/band_config_test.exs          | 39 ++++++++++-
 test/microwaveprop/propagation_test.exs       |  4 +-
 3 files changed, 102 insertions(+), 5 deletions(-)

diff --git a/lib/microwaveprop/propagation/band_config.ex b/lib/microwaveprop/propagation/band_config.ex
index 1009bd4b..4eebd0c9 100644
--- a/lib/microwaveprop/propagation/band_config.ex
+++ b/lib/microwaveprop/propagation/band_config.ex
@@ -48,6 +48,70 @@ defmodule Microwaveprop.Propagation.BandConfig do
   @refractivity_default {42, 42}
 
   @band_configs %{
+    # VHF / UHF bands share the tropo-ducting physics of low microwave
+    # (humidity and refractivity gradient build ducts the same way),
+    # so rain attenuation and gas absorption are effectively zero and
+    # humidity is :beneficial. The difference from 902+ is mostly in
+    # the achievable range — a 2m duct can reach 2500+ km under
+    # exceptional conditions (e.g. documented Hawaii ↔ California
+    # openings). These do NOT capture sporadic-E or meteor scatter,
+    # which need ionospheric data we don't yet ingest.
+    144 => %{
+      freq_mhz: 144,
+      label: "144 MHz",
+      o2_db_km: 0.0,
+      h2o_coeff: 0.0,
+      humidity_effect: :beneficial,
+      humidity_penalty: 0.0,
+      rain_k: 0.0,
+      rain_alpha: 1.0,
+      seasonal_base: %{
+        1 => 38,
+        2 => 40,
+        3 => 22,
+        4 => 55,
+        5 => 68,
+        6 => 90,
+        7 => 95,
+        8 => 75,
+        9 => 78,
+        10 => 88,
+        11 => 78,
+        12 => 25
+      },
+      seasonal_adj: %{},
+      typical_range_km: 350,
+      extended_range_km: 900,
+      exceptional_range_km: 2500
+    },
+    440 => %{
+      freq_mhz: 440,
+      label: "440 MHz",
+      o2_db_km: 0.0,
+      h2o_coeff: 0.0,
+      humidity_effect: :beneficial,
+      humidity_penalty: 0.0,
+      rain_k: 0.0,
+      rain_alpha: 1.0,
+      seasonal_base: %{
+        1 => 38,
+        2 => 40,
+        3 => 22,
+        4 => 55,
+        5 => 68,
+        6 => 90,
+        7 => 95,
+        8 => 75,
+        9 => 78,
+        10 => 88,
+        11 => 78,
+        12 => 25
+      },
+      seasonal_adj: %{},
+      typical_range_km: 300,
+      extended_range_km: 700,
+      exceptional_range_km: 1800
+    },
     902 => %{
       freq_mhz: 902,
       label: "902 MHz",
diff --git a/test/microwaveprop/propagation/band_config_test.exs b/test/microwaveprop/propagation/band_config_test.exs
index cebc4530..ef3c70ee 100644
--- a/test/microwaveprop/propagation/band_config_test.exs
+++ b/test/microwaveprop/propagation/band_config_test.exs
@@ -4,6 +4,8 @@ defmodule Microwaveprop.Propagation.BandConfigTest do
   alias Microwaveprop.Propagation.BandConfig
 
   @all_freqs [
+    144,
+    440,
     902,
     1_296,
     2_304,
@@ -116,6 +118,37 @@ defmodule Microwaveprop.Propagation.BandConfigTest do
       assert BandConfig.get(999) == nil
     end
 
+    test "returns config for 144 MHz (2m VHF)" do
+      config = BandConfig.get(144)
+      assert config.freq_mhz == 144
+      assert config.label == "144 MHz"
+      # Tropo ducting physics is the same as low microwave — humidity
+      # builds refractivity, rain and atmospheric absorption are
+      # negligible at VHF.
+      assert config.humidity_effect == :beneficial
+      assert config.humidity_penalty == 0.0
+      assert config.rain_k == 0.0
+      assert config.rain_alpha == 1.0
+      assert config.o2_db_km == 0.0
+      assert config.h2o_coeff == 0.0
+      # 2m tropo ducts can reach 2500+ km under exceptional conditions
+      # (e.g. documented Hawaii ↔ California openings).
+      assert config.exceptional_range_km >= 2000
+    end
+
+    test "returns config for 440 MHz (70cm UHF)" do
+      config = BandConfig.get(440)
+      assert config.freq_mhz == 440
+      assert config.label == "440 MHz"
+      assert config.humidity_effect == :beneficial
+      assert config.humidity_penalty == 0.0
+      assert config.rain_k == 0.0
+      assert config.rain_alpha == 1.0
+      assert config.h2o_coeff == 0.0
+      # 70cm tropo is strong but slightly less extreme than 2m.
+      assert config.exceptional_range_km >= 1500
+    end
+
     test "returns config for 142 GHz (between H2O 118 and 183 lines)" do
       config = BandConfig.get(142_000)
       assert config.freq_mhz == 142_000
@@ -150,9 +183,9 @@ defmodule Microwaveprop.Propagation.BandConfigTest do
   end
 
   describe "all_bands/0" do
-    test "returns 19 bands (13 original + 142, 145, 288, 322, 403, 411 GHz)" do
+    test "returns 21 bands (13 original + 142/145/288/322/403/411 GHz + 144/440 MHz)" do
       bands = BandConfig.all_bands()
-      assert length(bands) == 19
+      assert length(bands) == 21
     end
 
     test "bands are sorted by frequency" do
@@ -328,7 +361,7 @@ defmodule Microwaveprop.Propagation.BandConfigTest do
     end
 
     test "sub-10 GHz bands are beneficial, 24+ GHz are harmful" do
-      beneficial = [902, 1_296, 2_304, 3_456, 5_760, 10_000]
+      beneficial = [144, 440, 902, 1_296, 2_304, 3_456, 5_760, 10_000]
       harmful = @all_freqs -- beneficial
 
       for freq <- beneficial do
diff --git a/test/microwaveprop/propagation_test.exs b/test/microwaveprop/propagation_test.exs
index a51c3abc..e81191c6 100644
--- a/test/microwaveprop/propagation_test.exs
+++ b/test/microwaveprop/propagation_test.exs
@@ -32,7 +32,7 @@ defmodule Microwaveprop.PropagationTest do
       valid_time = ~U[2026-07-15 13:00:00Z]
       results = Propagation.score_grid_point(hrrr_profile, valid_time, 33.0, -97.0)
 
-      assert length(results) == 19
+      assert length(results) == 21
 
       Enum.each(results, fn result ->
         assert result.score >= 0 and result.score <= 100
@@ -98,7 +98,7 @@ defmodule Microwaveprop.PropagationTest do
       valid_time = ~U[2026-07-15 13:00:00Z]
       results = Propagation.score_grid_point(hrrr_profile_without_array, valid_time, 33.0, -97.0)
 
-      assert length(results) == 19
+      assert length(results) == 21
 
       Enum.each(results, fn result ->
         assert result.score >= 0 and result.score <= 100