diff --git a/lib/microwaveprop/pskr.ex b/lib/microwaveprop/pskr.ex
index 8852df23..9596f2f4 100644
--- a/lib/microwaveprop/pskr.ex
+++ b/lib/microwaveprop/pskr.ex
@@ -169,14 +169,12 @@ defmodule Microwaveprop.Pskr do
     }
   end
 
-  # Require ≥ 6-char locators on both ends. 4-char grids cover
-  # ~70 km × 100 km, so the midpoint and path distance error
-  # dwarfs any HRRR cell match (3 km native) and the resulting
-  # calibration sample geometry is meaningless. Drop the spot
-  # entirely rather than store a low-precision row.
+  # Require ≥ 4-char locators on both ends. 4-char grids cover
+  # ~70 km × 100 km — less precise for HRRR calibration but still
+  # useful for spot display and coarse path analysis.
   #
   # Maidenhead validity enforces even length + correct alphabet
-  # per position, so a passing string is a legal 6/8/10-char
+  # per position, so a passing string is a legal 4/6/8/10-char
   # locator we can store as-is. Uppercase for consistent indexing
   # — the unique key is case-sensitive.
   defp fetch_grid(json, key) do
@@ -186,7 +184,7 @@ defmodule Microwaveprop.Pskr do
 
         cond do
           not Maidenhead.valid?(upper) -> {:error, {:bad_grid, key, grid}}
-          String.length(upper) < 6 -> {:error, {:short_grid, key, grid}}
+          String.length(upper) < 4 -> {:error, {:short_grid, key, grid}}
           true -> {:ok, upper}
         end
 
diff --git a/test/microwaveprop/pskr_test.exs b/test/microwaveprop/pskr_test.exs
index df06803b..7d3cdbca 100644
--- a/test/microwaveprop/pskr_test.exs
+++ b/test/microwaveprop/pskr_test.exs
@@ -38,16 +38,14 @@ defmodule Microwaveprop.PskrTest do
       assert DateTime.to_unix(spot.transmit_time) == 1_662_407_697
     end
 
-    test "rejects 4-char grids on either end (insufficient precision)" do
-      # A 4-char locator is ~70 km × 100 km — the midpoint and
-      # distance error swamps any HRRR cell match (3 km native).
-      # Drop the spot rather than store a calibration sample whose
-      # geometry is meaningless.
-      sender_short = @sample |> Map.put("sl", "EM12") |> Jason.encode!()
-      receiver_short = @sample |> Map.put("rl", "DM43") |> Jason.encode!()
+    test "accepts 4-char grids on both ends" do
+      sender_4 = @sample |> Map.put("sl", "EM12") |> Jason.encode!()
+      receiver_4 = @sample |> Map.put("rl", "DM43") |> Jason.encode!()
 
-      assert {:error, _} = Pskr.parse_spot(sender_short)
-      assert {:error, _} = Pskr.parse_spot(receiver_short)
+      assert {:ok, spot} = Pskr.parse_spot(sender_4)
+      assert spot.sender_grid == "EM12"
+      assert {:ok, spot} = Pskr.parse_spot(receiver_4)
+      assert spot.receiver_grid == "DM43"
     end
 
     test "preserves extended-square (8-char) precision" do