diff --git a/app/src/main/java/com/geeksville/mesh/model/ChannelOption.kt b/app/src/main/java/com/geeksville/mesh/model/ChannelOption.kt
index 2ceae83ea..0f0e929e3 100644
--- a/app/src/main/java/com/geeksville/mesh/model/ChannelOption.kt
+++ b/app/src/main/java/com/geeksville/mesh/model/ChannelOption.kt
@@ -3,11 +3,11 @@ package com.geeksville.mesh.model
 import com.geeksville.mesh.MeshProtos
 import com.geeksville.mesh.R
 
-enum class ChannelOption(val modemConfig: MeshProtos.ChannelSettings.ModemConfig, val configRes: Int) {
-    SHORT(MeshProtos.ChannelSettings.ModemConfig.Bw500Cr45Sf128, R.string.modem_config_short),
-    MEDIUM(MeshProtos.ChannelSettings.ModemConfig.Bw125Cr45Sf128, R.string.modem_config_medium),
-    LONG(MeshProtos.ChannelSettings.ModemConfig.Bw31_25Cr48Sf512, R.string.modem_config_long),
-    VERY_LONG(MeshProtos.ChannelSettings.ModemConfig.Bw125Cr48Sf4096, R.string.modem_config_very_long);
+enum class ChannelOption(val modemConfig: MeshProtos.ChannelSettings.ModemConfig, val configRes: Int, val minBroadcastPeriodSecs: Int) {
+    SHORT(MeshProtos.ChannelSettings.ModemConfig.Bw500Cr45Sf128, R.string.modem_config_short, 3),
+    MEDIUM(MeshProtos.ChannelSettings.ModemConfig.Bw125Cr45Sf128, R.string.modem_config_medium, 12),
+    LONG(MeshProtos.ChannelSettings.ModemConfig.Bw31_25Cr48Sf512, R.string.modem_config_long, 240),
+    VERY_LONG(MeshProtos.ChannelSettings.ModemConfig.Bw125Cr48Sf4096, R.string.modem_config_very_long, 375);
 
     companion object {
         fun fromConfig(modemConfig: MeshProtos.ChannelSettings.ModemConfig?): ChannelOption? {
diff --git a/app/src/main/java/com/geeksville/mesh/ui/SettingsFragment.kt b/app/src/main/java/com/geeksville/mesh/ui/SettingsFragment.kt
index a582d3c5c..5d9ed9610 100644
--- a/app/src/main/java/com/geeksville/mesh/ui/SettingsFragment.kt
+++ b/app/src/main/java/com/geeksville/mesh/ui/SettingsFragment.kt
@@ -30,11 +30,11 @@ import com.geeksville.android.Logging
 import com.geeksville.android.hideKeyboard
 import com.geeksville.android.isGooglePlayAvailable
 import com.geeksville.mesh.MainActivity
-import com.geeksville.mesh.MeshProtos
 import com.geeksville.mesh.R
 import com.geeksville.mesh.android.bluetoothManager
 import com.geeksville.mesh.android.usbManager
 import com.geeksville.mesh.databinding.SettingsFragmentBinding
+import com.geeksville.mesh.model.ChannelOption
 import com.geeksville.mesh.model.UIViewModel
 import com.geeksville.mesh.service.BluetoothInterface
 import com.geeksville.mesh.service.MeshService
@@ -620,13 +620,22 @@ class SettingsFragment : ScreenFragment("Settings"), Logging {
         }
 
         binding.positionBroadcastPeriodEditText.on(EditorInfo.IME_ACTION_DONE) {
-            val str = binding.positionBroadcastPeriodEditText.text.toString()
-            val n = str.toIntOrNull()
-            if (n != null && n <= MAX_INT_DEVICE && n >= 0) {
-                model.positionBroadcastSecs = n
+            val textEdit = binding.positionBroadcastPeriodEditText
+            val n = textEdit.text.toString().toIntOrNull()
+            val minBroadcastPeriodSecs =
+                ChannelOption.fromConfig(model.radioConfig.value?.channelSettings?.modemConfig)?.minBroadcastPeriodSecs
+                    ?: 9000
+            info("edit broadcast $n min $minBroadcastPeriodSecs")
+            if (n != null && n >= 0 && n >= minBroadcastPeriodSecs) {
+                    model.positionBroadcastSecs = n
             } else {
-                binding.scanStatusText.text = "Bad value: $str"
+                // restore the value in the edit field
+                textEdit.setText(model.positionBroadcastSecs.toString())
+                val errorText = if (n == null || n <= 0) "Bad value: ${textEdit.text.toString()}" else
+                    getString(R.string.broadcast_period_too_small).format(minBroadcastPeriodSecs)
+                Toast.makeText(context, errorText, Toast.LENGTH_LONG).show()
             }
+
             requireActivity().hideKeyboard()
         }
 
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index de41846ff..af0fa2bca 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -86,4 +86,5 @@
     <string name="broadcast_position_secs">Broadcast position period (in seconds), 0 - disable</string>
     <string name="ls_sleep_secs">Device sleep period (in seconds)</string>
     <string name="meshtastic_messages_notifications">Notifications about messages</string>
+    <string name="broadcast_period_too_small">Minimum broadcast period for this channel is %d</string>
 </resources>