diff --git a/ntp_client_plus.cpp b/ntp_client_plus.cpp
index f272461..6892941 100644
--- a/ntp_client_plus.cpp
+++ b/ntp_client_plus.cpp
@@ -200,15 +200,14 @@ int NTPClientPlus::getSeconds() const
 String NTPClientPlus::getFormattedTime() const {
   unsigned long rawTime = this->getEpochTime();
   unsigned long hours = (rawTime % 86400L) / 3600;
-  String hoursStr = hours < 10 ? "0" + String(hours) : String(hours);
-
   unsigned long minutes = (rawTime % 3600) / 60;
-  String minuteStr = minutes < 10 ? "0" + String(minutes) : String(minutes);
-
   unsigned long seconds = rawTime % 60;
-  String secondStr = seconds < 10 ? "0" + String(seconds) : String(seconds);
 
-  return hoursStr + ":" + minuteStr + ":" + secondStr;
+  // Fester Puffer statt mehrfacher String-Verkettung, um Heap-Fragmentierung zu vermeiden
+  // Format identisch zu vorher: hh:mm:ss (jeweils 2-stellig, mit fuehrender Null)
+  char buffer[9]; // "hh:mm:ss" + '\0'
+  snprintf(buffer, sizeof(buffer), "%02lu:%02lu:%02lu", hours, minutes, seconds);
+  return String(buffer);
 }
 
 /**
@@ -732,4 +731,4 @@ bool NTPClientPlus::updateSWChange()
     }
 
     return summertimeActive;
-}
\ No newline at end of file
+}
diff --git a/udplogger.cpp b/udplogger.cpp
index 369af22..619afc7 100644
--- a/udplogger.cpp
+++ b/udplogger.cpp
@@ -10,21 +10,23 @@ UDPLogger::UDPLogger(IPAddress interfaceAddr, IPAddress multicastAddr, int port)
     _interfaceAddr = interfaceAddr;
     _name = "Log";
     _Udp.beginMulticast(_interfaceAddr, _multicastAddr, _port);
+    _lastSend = 0;
 }
 
 void UDPLogger::setName(String name){
     _name = name;
 }
 
-void UDPLogger::logString(String logmessage){
+void UDPLogger::logString(const String& logmessage){
     // wait 5 milliseconds if last send was less than 5 milliseconds before 
     if(millis() < (_lastSend + 5)){
         delay(5);
     }
-    logmessage = _name + ": " + logmessage;
-    Serial.println(logmessage);
+    // use fixed buffer instead of string concatenation to avoid heap fragmentation
+    // message will be truncated to fit into _packetBuffer (99 chars + NUL)
+    snprintf(_packetBuffer, sizeof(_packetBuffer), "%s: %s", _name.c_str(), logmessage.c_str());
+    Serial.println(_packetBuffer);
     _Udp.beginPacketMulticast(_multicastAddr, _port, _interfaceAddr);
-    logmessage.toCharArray(_packetBuffer, 100);
     _Udp.print(_packetBuffer);
     _Udp.endPacket();
     _lastSend=millis();
@@ -35,4 +37,4 @@ void UDPLogger::logColor24bit(uint32_t color){
   uint8_t resultGreen = color >> 8 & 0xff;
   uint8_t resultBlue = color & 0xff;
   logString(String(resultRed) + ", " + String(resultGreen) + ", " + String(resultBlue));
-}
\ No newline at end of file
+}
diff --git a/udplogger.h b/udplogger.h
index c26fa49..e4cac28 100644
--- a/udplogger.h
+++ b/udplogger.h
@@ -22,7 +22,7 @@ class UDPLogger{
         UDPLogger();
         UDPLogger(IPAddress interfaceAddr, IPAddress multicastAddr, int port);
         void setName(String name);
-        void logString(String logmessage);
+        void logString(const String& logmessage);
         void logColor24bit(uint32_t color);
     private:
         String _name;