diff --git a/lnxrouter b/lnxrouter
index a9d64a7..68e23a3 100755
--- a/lnxrouter
+++ b/lnxrouter
@@ -232,6 +232,7 @@ define_global_variables(){
     QR=0 # show wifi qr
     
     # script variables
+    PHY=
     VWIFI_IFACE=  # virtual wifi interface name, if created
     VIRT_NAME= # name to use for virtual interface if --virt-name is used
     AP_IFACE=     # can be VWIFI_IFACE or WIFI_IFACE
@@ -624,7 +625,6 @@ get_interface_phy_device() { # only for wifi interface
             return 0
         fi
     done
-    echo "Failed to get phy interface" >&2
     return 1
 }
 
@@ -689,20 +689,26 @@ can_transmit_to_channel() {
     fi
 }
 
-# taken from iw/util.c
 ieee80211_frequency_to_channel() {
     local FREQ=$1
-    if [[ $FREQ -eq 2484 ]]; then
+
+    # 2.4G
+    if [[ $FREQ -ge 2412 && $FREQ -le 2472 ]]; then # 2.4 GHz band: Channels 1-13 (2412~2472 MHz)
+        echo $(( (FREQ - 2407) / 5 ))
+    elif [[ $FREQ -eq 2484 ]]; then # 2.4 GHz Channel 14 (2484 MHz, Japan only)
         echo 14
-    elif [[ $FREQ -lt 2484 ]]; then
-        echo $(( ($FREQ - 2407) / 5 ))
-    elif [[ $FREQ -ge 4910 && $FREQ -le 4980 ]]; then
-        echo $(( ($FREQ - 4000) / 5 ))
-    elif [[ $FREQ -le 45000 ]]; then
-        echo $(( ($FREQ - 5000) / 5 ))
-    elif [[ $FREQ -ge 58320 && $FREQ -le 64800 ]]; then
-        echo $(( ($FREQ - 56160) / 2160 ))
-    else
+
+    # 5G
+    elif [[ $FREQ -ge 5160 && $FREQ -le 5885 ]]; then # 5 GHz band: Standard Channels 36-165 (5180~5825 MHz) (extra: 32, 169-177)
+        echo $(( (FREQ - 5000) / 5 ))
+
+    # 6G
+    elif [[ $FREQ -ge 5955 && $FREQ -le 7115 ]]; then # 6 GHz band: Channels 1-233 (5955~7115 MHz), Wi-Fi 6E/7
+        echo $(( (FREQ - 5950) / 5 ))
+    elif [[ $FREQ -eq 5935 ]]; then # 6 GHz band: Special case for 5935 MHz (Channel 2, rare)
+        echo 2
+
+    else # Frequency not in supported Wi-Fi bands (2.4/5/6 GHz)
         echo 0
     fi
 }
@@ -1706,9 +1712,14 @@ daemonizing_check(){
 
 #============================
 check_wifi_settings() {
+    PHY="$(get_interface_phy_device "$WIFI_IFACE")"
+    if [[ -z "$PHY" ]]; then
+        echo "ERROR: Can't get phy of wifi interface '$WIFI_IFACE' (Did you spell the interface name right?)" >&2
+        exit 1
+    fi
 
     if ! ( which iw > /dev/null 2>&1 && iw dev "$WIFI_IFACE" info > /dev/null 2>&1 ); then
-        echo "WARN: Can't use 'iw' to operate interfce '$WIFI_IFACE', trying 'iwconfig' (not as good as 'iw') ... (Did you spell the interface name right?)" >&2
+        echo "WARN: Can't use 'iw' to operate interfce '$WIFI_IFACE', trying 'iwconfig' (not as good as 'iw') ..." >&2
         USE_IWCONFIG=1
     fi
     
@@ -2208,10 +2219,8 @@ start_dnsmasq() {
 }
 
 check_rfkill_unblock_wifi() {
-    local PHY
     if which rfkill > /dev/null 2>&1 ; then
-        PHY=$(get_interface_phy_device "${SUBNET_IFACE}")
-        [[ -n $PHY ]] && rfkill unblock $(rfkill | grep "$PHY" | awk '{print $1}') >/dev/null 2>&1
+        rfkill unblock $(rfkill | grep "$PHY" | awk '{print $1}') >/dev/null 2>&1
     fi
 }
 
@@ -2293,7 +2302,7 @@ fi
 
 # judge channel availability after changing country code
 if [[ $WIFI_IFACE ]] ; then
-    can_transmit_to_channel "${AP_IFACE}" ${CHANNEL} || die "Your adapter can not transmit to channel ${CHANNEL}, frequency band ${FREQ_BAND}GHz."
+    can_transmit_to_channel "${AP_IFACE}" ${CHANNEL} || die "Your adapter can not transmit to channel ${CHANNEL}, frequency band ${FREQ_BAND}GHz. (Tips: 1. Check usable channels: 'iw phy $PHY info'.  2. Check country code then check again.  )"
 fi
 
 [[ $WIFI_IFACE ]] && write_hostapd_conf