diff --git a/include/if482.h b/include/if482.h
index def3a2fe..b38013d8 100644
--- a/include/if482.h
+++ b/include/if482.h
@@ -6,5 +6,7 @@
 
 int if482_init(void);
 void if482_loop(void *pvParameters);
+TickType_t tx_time(unsigned long baud, uint32_t config, int8_t rxPin,
+                   int8_t txPins);
 
 #endif
\ No newline at end of file
diff --git a/src/dcf77.cpp b/src/dcf77.cpp
index 8be4ed61..f77486c5 100644
--- a/src/dcf77.cpp
+++ b/src/dcf77.cpp
@@ -39,6 +39,7 @@ int dcf77_init(void) {
 
   pinMode(HAS_DCF77, OUTPUT);
   set_DCF77_pin(dcf_low);
+  timepulse_init(PPS); // setup timepulse
 
   xTaskCreatePinnedToCore(dcf77_loop,  // task function
                           "dcf77loop", // name of task
@@ -49,8 +50,6 @@ int dcf77_init(void) {
                           0);          // CPU core
 
   assert(ClockTask); // has clock task started?
-
-  timepulse_init(PPS);        // setup pulse
   DCF_Out(sync_clock(now())); // sync DCF time on next second
   timepulse_start();          // start pulse
 
diff --git a/src/if482.cpp b/src/if482.cpp
index 97aff8c4..c08cdec3 100644
--- a/src/if482.cpp
+++ b/src/if482.cpp
@@ -107,6 +107,8 @@ int if482_init(void) {
 
   // open serial interface
   IF482.begin(HAS_IF482);
+  // setup timepulse
+  timepulse_init(PPS);
 
   // start if482 serial output feed task
   xTaskCreatePinnedToCore(if482_loop,  // task function
@@ -118,9 +120,7 @@ int if482_init(void) {
                           0);          // CPU core
 
   assert(ClockTask); // has clock task started?
-
-  timepulse_init(PPS); // setup pulse
-  timepulse_start();   // start pulse
+  timepulse_start(); // start pulse
 
   return 1; // success
 } // if482_init
@@ -161,7 +161,7 @@ void if482_loop(void *pvParameters) {
 
   TickType_t wakeTime;
   const TickType_t timeOffset =
-      pdMS_TO_TICKS(IF482_OFFSET); // duration of telegram transmit
+      tx_time(HAS_IF482); // duration of telegram transmit
   const TickType_t startTime = xTaskGetTickCount(); // now
 
   sync_clock(now());  // wait until begin of a new second
@@ -196,4 +196,15 @@ void if482_loop(void *pvParameters) {
   }
 } // if482_loop()
 
+// helper function to calculate IF482 telegram serial tx time from serial
+// settings
+TickType_t tx_time(unsigned long baud, uint32_t config, int8_t rxPin,
+                   int8_t txPins) {
+
+  uint32_t datenbits = ((config & 0x0c) >> 2) + 5;
+  uint32_t startbits = ((config & 0x20) >> 5) + 1;
+  return pdMS_TO_TICKS(
+      round(((datenbits + startbits + 1) * IF482_FRAME_SIZE * 1000.0 / baud)));
+}
+
 #endif // HAS_IF482
\ No newline at end of file
diff --git a/src/paxcounter.conf b/src/paxcounter.conf
index 1b6d6c3a..555a0491 100644
--- a/src/paxcounter.conf
+++ b/src/paxcounter.conf
@@ -82,12 +82,11 @@
 #define RESPONSE_TIMEOUT_MS             60000   // firmware binary server connection timeout [milliseconds]
 
 // settings for syncing time of node and external time sources
-#define TIME_SYNC_INTERVAL_GPS          60      // sync time each .. minutes from source GPS [default = 60], comment out means off          
+#define TIME_SYNC_INTERVAL_GPS          5       // sync time each .. minutes from source GPS [default = 5], comment out means off          
 #define TIME_SYNC_INTERVAL_RTC          60      // sync time each .. minutes from RTC [default = 60], comment out means off          
 #define TIME_WRITE_INTERVAL_RTC         60      // write time each .. minutes from GPS/LORA to RTC [default = 60], comment out means off          
 //#define TIME_SYNC_INTERVAL_LORA       60      // sync time each .. minutes from LORA network [default = 60], comment out means off
 #define TIME_SYNC_INTERVAL_DCF          60      // sync DCF signal time each .. minutes from internal time [default = 60], comment out means off    
-#define IF482_OFFSET                    16      // IF482 serial transmit time [ms]: e.g. 9 bits * 17 bytes * 1/9600 bps = 16ms
 
 // time zone, see https://github.com/JChristensen/Timezone/blob/master/examples/WorldClock/WorldClock.ino
 #define DAYLIGHT_TIME                   {"CEST", Last, Sun, Mar, 2, 120}     // Central European Summer Time
diff --git a/src/rtctime.cpp b/src/rtctime.cpp
index d59f574b..7c120ac7 100644
--- a/src/rtctime.cpp
+++ b/src/rtctime.cpp
@@ -136,6 +136,7 @@ int timepulse_init(uint32_t pulse_period_ms) {
       Rtc.SetSquareWavePinClockFrequency(DS3231SquareWaveClock_1kHz);
       break;
     default:
+      I2C_MUTEX_UNLOCK();
       goto pulse_period_error;
     }
     Rtc.SetSquareWavePin(DS3231SquareWavePin_ModeClock);