diff --git a/CONTRIBUTORS b/CONTRIBUTORS
index aa2d9967..904526f2 100644
--- a/CONTRIBUTORS
+++ b/CONTRIBUTORS
@@ -3652,6 +3652,7 @@ Helmut Binder <cco@aon.at>
  for reporting a problem with PMT handling in case locking the Channels list times out
  for avoiding a lengthy lock on the Channels list when starting a recording
  for preventing switching devices for pattern timers
+ for pointing out that cChannel::Transponder(void) is called very often
 
 Ulrich Eckhardt <uli@uli-eckhardt.de>
  for reporting a problem with shutdown after user inactivity in case a plugin is
diff --git a/HISTORY b/HISTORY
index 39733817..8c80f4a1 100644
--- a/HISTORY
+++ b/HISTORY
@@ -9663,7 +9663,7 @@ Video Disk Recorder Revision History
 - EXPIRELATENCY now only applies to VPS timers.
 - Deleting expired timers is now triggered immediately after the timers are modified.
 
-2021-05-20:
+2021-05-21:
 
 - Now using a separate fixed value for internal EPG linger time. This fixes problems with
   spawned timers jumping to the next event in case Setup.EPGLinger is very small. (reported
@@ -9688,3 +9688,5 @@ Video Disk Recorder Revision History
   + It was only actually used in svdrp.c.
   + cFile::Ready() now processes only its own file descriptor by calling FileReady()
     instead of AnyFileReady().
+- The transponder value of channels is now cached, because cChannel::Transponder(void)
+  is called very often (pointed out by Helmut Binder).
diff --git a/channels.c b/channels.c
index 606ed8ff..7fe8275d 100644
--- a/channels.c
+++ b/channels.c
@@ -4,7 +4,7 @@
  * See the main source file 'vdr.c' for copyright information and
  * how to reach the author.
  *
- * $Id: channels.c 4.6 2020/04/11 09:22:05 kls Exp $
+ * $Id: channels.c 5.1 2021/05/21 09:38:34 kls Exp $
  */
 
 #include "channels.h"
@@ -145,15 +145,18 @@ int cChannel::Transponder(int Frequency, char Polarization)
 
 int cChannel::Transponder(void) const
 {
-  int tf = frequency;
-  while (tf > 20000)
-        tf /= 1000;
-  if (IsSat()) {
-     const char *p = strpbrk(parameters, "HVLRhvlr"); // lowercase for backwards compatibility
-     if (p)
-        tf = Transponder(tf, *p);
+  if (!transponder) {
+     int tf = frequency;
+     while (tf > 20000)
+           tf /= 1000;
+     if (IsSat()) {
+        const char *p = strpbrk(parameters, "HVLRhvlr"); // lowercase for backwards compatibility
+        if (p)
+           tf = Transponder(tf, *p);
+        }
+     transponder = tf;
      }
-  return tf;
+  return transponder;
 }
 
 int cChannel::Modification(int Mask) const
@@ -167,6 +170,7 @@ void cChannel::CopyTransponderData(const cChannel *Channel)
 {
   if (Channel) {
      frequency    = Channel->frequency;
+     transponder  = Channel->transponder;
      source       = Channel->source;
      srate        = Channel->srate;
      parameters   = Channel->parameters;
@@ -195,6 +199,7 @@ bool cChannel::SetTransponderData(int Source, int Frequency, int Srate, const ch
      cString OldTransponderData = TransponderDataToString();
      source = Source;
      frequency = Frequency;
+     transponder = 0;
      srate = Srate;
      parameters = Parameters;
      schedule = NULL;
@@ -655,6 +660,7 @@ bool cChannel::Parse(const char *s)
         if (parambuf && sourcebuf && vpidbuf && apidbuf) {
            parameters = parambuf;
            ok = (source = cSource::FromString(sourcebuf)) >= 0;
+           transponder = 0;
 
            char *p;
            if ((p = strchr(vpidbuf, '=')) != NULL) {
diff --git a/channels.h b/channels.h
index dd16b351..25ddc3d1 100644
--- a/channels.h
+++ b/channels.h
@@ -4,7 +4,7 @@
  * See the main source file 'vdr.c' for copyright information and
  * how to reach the author.
  *
- * $Id: channels.h 5.1 2021/01/14 10:29:05 kls Exp $
+ * $Id: channels.h 5.2 2021/05/21 09:38:34 kls Exp $
  */
 
 #ifndef __CHANNELS_H
@@ -96,6 +96,7 @@ private:
   char *portalName;
   int __BeginData__;
   int frequency; // MHz
+  mutable int transponder; // cached value
   int source;
   int srate;
   int vpid;