diff --git a/htdocs/lib/Scanner.js b/htdocs/lib/Scanner.js
index 87170fda..23b6257e 100644
--- a/htdocs/lib/Scanner.js
+++ b/htdocs/lib/Scanner.js
@@ -2,22 +2,16 @@ function Scanner(bookmarkBar, msec) {
     this.bbar      = bookmarkBar;
     this.bookmarks = null;
     this.msec      = msec;
-    this.current   = null;
+    this.current   = -1;
     this.threshold = -80;
-    this.data      = [];
 }
 
 Scanner.prototype.tuneBookmark = function(b) {
     // Must have frequency, skip digital voice modes
-    if (!b || !b.frequency || !b.modulation || b.modulation=='dmr') {
-        return false;
-    }
+    if (!b.frequency || !b.modulation || b.modulation=='dmr') return false;
 
     //console.log("TUNE: " + b.name + " at " + b.frequency + ": " + b.modulation);
 
-    // Make this bookmark current
-    this.current = b;
-
     // Tune to the bookmark frequency
     var panel = $('#openwebrx-panel-receiver').demodulatorPanel();
     panel.getDemodulator().set_offset_frequency(b.frequency - center_freq);
@@ -27,58 +21,45 @@ Scanner.prototype.tuneBookmark = function(b) {
     return true;
 }
 
-Scanner.prototype.getLevel = function(b) {
-    // Must have bookmark and frequency
-    if(!b || !b.frequency || !this.data.length) return -1000;
-
-    // Compute relevant FFT slot index
-    var x = this.data.length * ((b.frequency - center_freq) / bandwidth + 0.5);
-    return this.data[x | 0];
-}
-
 Scanner.prototype.update = function(data) {
-    // Do not update if no timer
-    if (!this.timer) return;
+    // Do not update if no timer or no bookmarks
+    if (!this.timer || !this.bookmarks || !this.bookmarks.length) return;
 
-    var i = this.data.length < data.length? this.data.length : data.length;
-
-    // Truncate stored data length, add and fill missing data
-    if (this.data.length > i) {
-        this.data.length = i;
-    } else if(this.data.length < data.length) {
-        this.data.length = data.length;
-        for(var j=i; j<data.length; ++j) this.data[j] = data[j];
+    // Average level over time for each bookmark
+    for(var j=0 ; j<this.bookmarks.length ; ++j) {
+        var b = this.bookmarks[j];
+        if (b.frequency > 0) {
+            var l = data[(b.pos * data.length) | 0];
+            b.level += (l - b.level) / 5.0;
+        }
     }
-
-    // Average level over time
-    for(var j=0; j<i; ++j) this.data[j] += (data[j] - this.data[j]) / 10.0;
 }
 
 Scanner.prototype.scan = function() {
-    // Do not scan if no timer or no data
-    if (!this.bookmarks || !this.bookmarks.length) return;
-    if (!this.timer || !this.data.length) return;
+    // Do not scan if no timer or no bookmarks
+    if (!this.timer || !this.bookmarks || !this.bookmarks.length) return;
 
     // Get current squelch threshold from the slider
     var $slider = $('#openwebrx-panel-receiver .openwebrx-squelch-slider');
     this.threshold = $slider.val();
 
     // If there is currently selected bookmark...
-    if (this.current) {
-        var level = this.getLevel(this.current);
-        if (level>this.threshold) return; else this.current = null;
+    if (this.current>=0) {
+        var level = this.bookmarks[this.current].level;
+        if (level>this.threshold) return; else this.current = -1;
     }
 
     // For every shown bookmark...
     for(var j=0 ; j<this.bookmarks.length ; ++j) {
-        // Get bookmark's current level
         var b = this.bookmarks[j];
-        var level = this.getLevel(b);
 
-        //console.log("SCAN: " + b.name + " at " + b.frequency + ": " + level);
+        //console.log("SCAN: " + b.name + " at " + b.frequency + ": " + b.level);
 
         // If level exceeds threshold, tune to the bookmark
-        if (level>this.threshold && this.tuneBookmark(b)) return;
+        if (b.level>this.threshold && this.tuneBookmark(b)) {
+            this.current = j;
+            return;
+        }
     }
 };
 
@@ -88,10 +69,8 @@ Scanner.prototype.stop = function() {
         // Stop redraw timer
         clearInterval(this.timer);
         this.timer = 0;
-        // Remove current bookmarks and data
+        // Remove current bookmarks
         this.bookmarks = null;
-        this.current = null;
-        this.data.length = 0;
     }
 
     // Done
@@ -103,9 +82,17 @@ Scanner.prototype.start = function() {
     if (!this.timer) {
         // Get all bookmarks from the bookmark bar
         this.bookmarks = this.bbar.getAllBookmarks();
+        this.current   = -1;
 
         // If there are bookmarks to scan...
         if (this.bookmarks && this.bookmarks.length>0) {
+            // Precompute FFT offsets, initialize levels
+            for(var j=0 ; j<this.bookmarks.length ; ++j) {
+                var f = this.bookmarks[j].frequency;
+                this.bookmarks[j].level = -1000;
+                this.bookmarks[j].pos = f>0? (f - center_freq) / bandwidth + 0.5 : 0;
+            }
+
             // Start redraw timer
             var me = this;
             this.timer = setInterval(function() { me.scan(); }, this.msec);
diff --git a/htdocs/openwebrx.js b/htdocs/openwebrx.js
index fdbfd24d..e39445c5 100644
--- a/htdocs/openwebrx.js
+++ b/htdocs/openwebrx.js
@@ -1051,6 +1051,7 @@ function on_ws_recv(evt) {
                             currentprofile['profile_id'] = config['profile_id'] || currentprofile['profile_id'];
                             $('#openwebrx-sdr-profiles-listbox').val(currentprofile.toString());
 
+                            stopScanner();
                             tuning_step_reset();
                             waterfall_clear();
                             zoom_set(0);
@@ -1710,6 +1711,11 @@ function toggleSpectrum() {
     spectrum.toggle();
 }
 
+function stopScanner() {
+    $('.openwebrx-scan-button').css('animation-name', '');
+    scanner.stop();
+}
+
 function toggleScanner() {
     var $scanButton = $('.openwebrx-scan-button');
     var on = scanner.toggle();