diff --git a/armsrc/appmain.c b/armsrc/appmain.c
index 3793182ce..c5cdc5dc7 100644
--- a/armsrc/appmain.c
+++ b/armsrc/appmain.c
@@ -108,7 +108,7 @@ void ToSendStuffBit(int b) {
 
 //-----------------------------------------------------------------------------
 // Read an ADC channel and block till it completes, then return the result
-// in ADC units (0 to 1023). Also a routine to average 32 samples and
+// in ADC units (0 to 1023). Also a routine to sum up a number of samples and
 // return that.
 //-----------------------------------------------------------------------------
 static uint16_t ReadAdc(int ch) {
@@ -138,12 +138,14 @@ static uint16_t ReadAdc(int ch) {
 
 // was static - merlok
 uint16_t AvgAdc(int ch) {
-    uint16_t a = 0;
-    for (uint8_t i = 0; i < 32; i++)
-        a += ReadAdc(ch);
+    return SumAdc(ch, 32) >> 5;
+}
 
-    //division by 32
-    return (a + 15) >> 5;
+uint16_t SumAdc(int ch, int NbSamples) {
+    uint16_t a = 0;
+    for (uint8_t i = 0; i < NbSamples; i++)
+        a += ReadAdc(ch);
+    return (a + (NbSamples >> 1) - 1);
 }
 
 static void MeasureAntennaTuning(void) {
@@ -186,7 +188,7 @@ static void MeasureAntennaTuning(void) {
         WDT_HIT();
         FpgaSendCommand(FPGA_CMD_SET_DIVISOR, i);
         SpinDelay(20);
-        uint32_t adcval = ((MAX_ADC_LF_VOLTAGE * AvgAdc(ADC_CHAN_LF)) >> 10);
+        uint32_t adcval = ((MAX_ADC_LF_VOLTAGE * (SumAdc(ADC_CHAN_LF, 32) >> 1)) >> 14);
         if (i == LF_DIVISOR_125)
             payload.v_lf125 = adcval; // voltage at 125kHz
 
@@ -212,9 +214,9 @@ static void MeasureAntennaTuning(void) {
     SpinDelay(50);
 
 #if defined RDV4
-    payload.v_hf = (MAX_ADC_HF_VOLTAGE_RDV40 * AvgAdc(ADC_CHAN_HF_RDV40)) >> 10;
+    payload.v_hf = (MAX_ADC_HF_VOLTAGE_RDV40 * SumAdc(ADC_CHAN_HF_RDV40, 32)) >> 15;
 #else
-    payload.v_hf = (MAX_ADC_HF_VOLTAGE * AvgAdc(ADC_CHAN_HF)) >> 10;
+    payload.v_hf = (MAX_ADC_HF_VOLTAGE * SumAdc(ADC_CHAN_HF, 32)) >> 15;
 #endif
 
     FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
@@ -226,16 +228,16 @@ static void MeasureAntennaTuning(void) {
 static uint16_t MeasureAntennaTuningHfData(void) {
 
 #if defined RDV4
-    return (MAX_ADC_HF_VOLTAGE_RDV40 * AvgAdc(ADC_CHAN_HF_RDV40)) >> 10;
+    return (MAX_ADC_HF_VOLTAGE_RDV40 * SumAdc(ADC_CHAN_HF_RDV40, 32)) >> 15;
 #else
-    return (MAX_ADC_HF_VOLTAGE * AvgAdc(ADC_CHAN_HF)) >> 10;
+    return (MAX_ADC_HF_VOLTAGE * SumAdc(ADC_CHAN_HF, 32)) >> 15;
 #endif
 
 }
 
 // Measure LF in milliVolt
 static uint32_t MeasureAntennaTuningLfData(void) {
-    return (MAX_ADC_LF_VOLTAGE * AvgAdc(ADC_CHAN_LF)) >> 10;
+    return (MAX_ADC_LF_VOLTAGE * (SumAdc(ADC_CHAN_LF, 32) >> 1)) >> 14;
 }
 
 void ReadMem(int addr) {
diff --git a/armsrc/appmain.h b/armsrc/appmain.h
index 5aece8388..6a650f163 100644
--- a/armsrc/appmain.h
+++ b/armsrc/appmain.h
@@ -31,6 +31,7 @@ void ReadMem(int addr);
 void __attribute__((noreturn)) AppMain(void);
 
 uint16_t AvgAdc(int ch);
+uint16_t SumAdc(int ch, int NbSamples);
 
 //void PrintToSendBuffer(void);
 void ToSendStuffBit(int b);
diff --git a/armsrc/iso14443b.c b/armsrc/iso14443b.c
index bbca137fc..4999c4d85 100644
--- a/armsrc/iso14443b.c
+++ b/armsrc/iso14443b.c
@@ -641,9 +641,9 @@ void SimulateIso14443bTag(uint32_t pupi) {
         if (cardSTATE == SIM_NOFIELD) {
 
 #if defined RDV4
-            vHf = (MAX_ADC_HF_VOLTAGE_RDV40 * AvgAdc(ADC_CHAN_HF_RDV40)) >> 10;
+            vHf = (MAX_ADC_HF_VOLTAGE_RDV40 * SumAdc(ADC_CHAN_HF_RDV40, 32)) >> 15;
 #else
-            vHf = (MAX_ADC_HF_VOLTAGE * AvgAdc(ADC_CHAN_HF)) >> 10;
+            vHf = (MAX_ADC_HF_VOLTAGE * SumAdc(ADC_CHAN_HF, 32)) >> 15;
 #endif
             if (vHf > MF_MINFIELDV) {
                 cardSTATE = SIM_IDLE;
diff --git a/armsrc/lfops.c b/armsrc/lfops.c
index 9ef3a34a8..72559a7b9 100644
--- a/armsrc/lfops.c
+++ b/armsrc/lfops.c
@@ -1571,7 +1571,7 @@ void TurnReadLFOn(uint32_t delay) {
     FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_READER | FPGA_LF_ADC_READER_FIELD);
 
     // measure antenna strength.
-    //int adcval = ((MAX_ADC_LF_VOLTAGE * AvgAdc(ADC_CHAN_LF)) >> 10);
+    //int adcval = ((MAX_ADC_LF_VOLTAGE * (SumAdc(ADC_CHAN_LF, 32) >> 1)) >> 14);
     WaitUS(delay);
 }
 static void TurnReadLF_off(uint32_t delay) {
diff --git a/armsrc/mifaresim.c b/armsrc/mifaresim.c
index ecc0ee505..60f9a7810 100644
--- a/armsrc/mifaresim.c
+++ b/armsrc/mifaresim.c
@@ -539,9 +539,9 @@ void Mifare1ksim(uint16_t flags, uint8_t exitAfterNReads, uint8_t *datain, uint1
         if (cardSTATE == MFEMUL_NOFIELD) {
 
 #if defined RDV4
-            vHf = (MAX_ADC_HF_VOLTAGE_RDV40 * AvgAdc(ADC_CHAN_HF_RDV40)) >> 10;
+            vHf = (MAX_ADC_HF_VOLTAGE_RDV40 * SumAdc(ADC_CHAN_HF_RDV40, 32)) >> 15;
 #else
-            vHf = (MAX_ADC_HF_VOLTAGE * AvgAdc(ADC_CHAN_HF)) >> 10;
+            vHf = (MAX_ADC_HF_VOLTAGE * SumAdc(ADC_CHAN_HF, 32)) >> 15;
 #endif
 
             if (vHf > MF_MINFIELDV) {