diff --git a/assets/js/contacts_map_hook.ts b/assets/js/contacts_map_hook.ts
index 0e36ea2e..c7c205e2 100644
--- a/assets/js/contacts_map_hook.ts
+++ b/assets/js/contacts_map_hook.ts
@@ -25,7 +25,7 @@ interface ContactsMapHook extends ViewHook {
 const BAND_COLORS: Record<number, string> = {
   1296:   "#475569", // slate-600
   2304:   "#7c3aed", // violet-600
-  3456:   "#4f46e5", // indigo-600
+  3400:   "#4f46e5", // indigo-600
   5760:   "#2563eb", // blue-600
   10000:  "#059669", // emerald-600
   24000:  "#d97706", // amber-600
diff --git a/lib/microwaveprop/propagation/band_config.ex b/lib/microwaveprop/propagation/band_config.ex
index 7d6f9519..a7ad03f2 100644
--- a/lib/microwaveprop/propagation/band_config.ex
+++ b/lib/microwaveprop/propagation/band_config.ex
@@ -253,9 +253,9 @@ defmodule Microwaveprop.Propagation.BandConfig do
       extended_range_km: 600,
       exceptional_range_km: 1000
     },
-    3_456 => %{
-      freq_mhz: 3_456,
-      label: "3456 MHz",
+    3_400 => %{
+      freq_mhz: 3_400,
+      label: "3400 MHz",
       o2_db_km: 0.006,
       h2o_coeff: 0.0,
       humidity_effect: :beneficial,
diff --git a/lib/microwaveprop/radio/band_resolver.ex b/lib/microwaveprop/radio/band_resolver.ex
index 56c48db5..597fcaae 100644
--- a/lib/microwaveprop/radio/band_resolver.ex
+++ b/lib/microwaveprop/radio/band_resolver.ex
@@ -21,7 +21,7 @@ defmodule Microwaveprop.Radio.BandResolver do
     902,
     1296,
     2304,
-    3456,
+    3400,
     5760,
     10_000,
     24_000,
@@ -44,7 +44,7 @@ defmodule Microwaveprop.Radio.BandResolver do
     "33cm" => 902,
     "23cm" => 1_296,
     "13cm" => 2_304,
-    "9cm" => 3_456,
+    "9cm" => 3_400,
     "6cm" => 5_760,
     "3cm" => 10_000,
     "1.25cm" => 24_000,
diff --git a/lib/microwaveprop/radio/contact.ex b/lib/microwaveprop/radio/contact.ex
index 037a8e98..a91f7092 100644
--- a/lib/microwaveprop/radio/contact.ex
+++ b/lib/microwaveprop/radio/contact.ex
@@ -65,7 +65,7 @@ defmodule Microwaveprop.Radio.Contact do
   # Keep in sync with Microwaveprop.Propagation.BandConfig.all_bands/0 and
   # Microwaveprop.Radio.AdifImport.@allowed_bands.
   @allowed_bands Enum.map(
-                   ~w(50 144 222 432 902 1296 2304 3456 5760 10000 24000 47000 68000 75000 122000 134000 241000),
+                   ~w(50 144 222 432 902 1296 2304 3400 5760 10000 24000 47000 68000 75000 122000 134000 241000),
                    &Decimal.new/1
                  )
 
diff --git a/lib/microwaveprop/radio/contact_edit.ex b/lib/microwaveprop/radio/contact_edit.ex
index bd035c2f..520f5bed 100644
--- a/lib/microwaveprop/radio/contact_edit.ex
+++ b/lib/microwaveprop/radio/contact_edit.ex
@@ -12,7 +12,7 @@ defmodule Microwaveprop.Radio.ContactEdit do
   @foreign_key_type :binary_id
 
   @allowed_modes ~w(CW SSB FM FT8 FT4 Q65)
-  @allowed_bands ~w(902 1296 2304 3456 5760 10000 24000 47000 68000 75000 122000 134000 241000)
+  @allowed_bands ~w(50 144 222 432 902 1296 2304 3400 5760 10000 24000 47000 68000 75000 122000 134000 241000)
 
   schema "contact_edits" do
     belongs_to :contact, Contact
diff --git a/lib/microwaveprop_web/live/contact_map_live.ex b/lib/microwaveprop_web/live/contact_map_live.ex
index 398ddff8..4f9e7aa8 100644
--- a/lib/microwaveprop_web/live/contact_map_live.ex
+++ b/lib/microwaveprop_web/live/contact_map_live.ex
@@ -7,7 +7,7 @@ defmodule MicrowavepropWeb.ContactMapLive do
   @band_colors %{
     1296 => "#475569",
     2304 => "#7c3aed",
-    3456 => "#4f46e5",
+    3400 => "#4f46e5",
     5760 => "#2563eb",
     10_000 => "#059669",
     24_000 => "#d97706",
diff --git a/priv/repo/migrations/20260416173951_rename_band_3456_to_3400.exs b/priv/repo/migrations/20260416173951_rename_band_3456_to_3400.exs
new file mode 100644
index 00000000..5f80b6c4
--- /dev/null
+++ b/priv/repo/migrations/20260416173951_rename_band_3456_to_3400.exs
@@ -0,0 +1,14 @@
+defmodule Microwaveprop.Repo.Migrations.RenameBand3456To3400 do
+  use Ecto.Migration
+
+  # US 9cm amateur allocation was cut from 3300-3500 to 3300-3450 MHz in
+  # 2020, so the legacy 3456 weak-signal calling frequency is no longer
+  # in-band. Canonicalize existing contacts on the new 3400 value.
+  def up do
+    execute "UPDATE contacts SET band = 3400 WHERE band = 3456"
+  end
+
+  def down do
+    execute "UPDATE contacts SET band = 3456 WHERE band = 3400"
+  end
+end
diff --git a/test/microwaveprop/propagation/band_config_test.exs b/test/microwaveprop/propagation/band_config_test.exs
index d308dccf..8aabc573 100644
--- a/test/microwaveprop/propagation/band_config_test.exs
+++ b/test/microwaveprop/propagation/band_config_test.exs
@@ -11,7 +11,7 @@ defmodule Microwaveprop.Propagation.BandConfigTest do
     902,
     1_296,
     2_304,
-    3_456,
+    3_400,
     5_760,
     10_000,
     24_000,
@@ -363,7 +363,7 @@ defmodule Microwaveprop.Propagation.BandConfigTest do
     end
 
     test "sub-10 GHz bands are beneficial, 24+ GHz are harmful" do
-      beneficial = [50, 144, 222, 432, 902, 1_296, 2_304, 3_456, 5_760, 10_000]
+      beneficial = [50, 144, 222, 432, 902, 1_296, 2_304, 3_400, 5_760, 10_000]
       harmful = @all_freqs -- beneficial
 
       for freq <- beneficial do
diff --git a/test/microwaveprop/radio/band_resolver_test.exs b/test/microwaveprop/radio/band_resolver_test.exs
new file mode 100644
index 00000000..8bc085a1
--- /dev/null
+++ b/test/microwaveprop/radio/band_resolver_test.exs
@@ -0,0 +1,53 @@
+defmodule Microwaveprop.Radio.BandResolverTest do
+  use ExUnit.Case, async: true
+
+  alias Microwaveprop.Radio.BandResolver
+
+  describe "resolve/1" do
+    test "resolves wavelength labels" do
+      assert BandResolver.resolve("6m") == 50
+      assert BandResolver.resolve("2m") == 144
+      assert BandResolver.resolve("1.25m") == 222
+      assert BandResolver.resolve("70cm") == 432
+      assert BandResolver.resolve("9cm") == 3_400
+      assert BandResolver.resolve("3cm") == 10_000
+    end
+
+    test "resolves canonical values through passthrough" do
+      for band <- BandResolver.allowed_bands() do
+        assert BandResolver.resolve(band) == band
+        assert BandResolver.resolve(Integer.to_string(band)) == band
+      end
+    end
+
+    test "resolves the legacy 3456 MHz calling frequency to the current 9cm band" do
+      # 9cm was cut from 3300-3500 to 3300-3450 MHz in 2020, so the old
+      # weak-signal calling frequency 3456 is no longer in the allocation
+      # but historical logs still carry it.
+      assert BandResolver.resolve("3456") == 3_400
+      assert BandResolver.resolve(3456) == 3_400
+      assert BandResolver.resolve(3456.1) == 3_400
+    end
+
+    test "snaps near-band frequencies to amateur allocations" do
+      assert BandResolver.resolve("50.125") == 50
+      assert BandResolver.resolve("144.200") == 144
+      assert BandResolver.resolve("222.100") == 222
+      assert BandResolver.resolve("432.100") == 432
+      assert BandResolver.resolve("10368.100") == 10_000
+    end
+
+    test "returns nil for HF and gaps between amateur bands" do
+      assert BandResolver.resolve("14.200") == nil
+      assert BandResolver.resolve("28.400") == nil
+      assert BandResolver.resolve("500") == nil
+      assert BandResolver.resolve("800") == nil
+    end
+
+    test "returns nil for unparseable input" do
+      assert BandResolver.resolve(nil) == nil
+      assert BandResolver.resolve("") == nil
+      assert BandResolver.resolve("banana") == nil
+    end
+  end
+end
diff --git a/test/microwaveprop/radio/contact_submission_test.exs b/test/microwaveprop/radio/contact_submission_test.exs
index 9edf5173..e255a2c8 100644
--- a/test/microwaveprop/radio/contact_submission_test.exs
+++ b/test/microwaveprop/radio/contact_submission_test.exs
@@ -84,7 +84,7 @@ defmodule Microwaveprop.Radio.ContactSubmissionTest do
     end
 
     test "accepts valid bands" do
-      for band <- ~w(50 144 222 432 902 1296 2304 3456 5760 10000 24000 47000 75000) do
+      for band <- ~w(50 144 222 432 902 1296 2304 3400 5760 10000 24000 47000 75000) do
         attrs = Map.put(@valid_attrs, :band, band)
         changeset = Contact.submission_changeset(%Contact{}, attrs)
         assert changeset.valid?, "Expected band #{band} to be valid"