diff --git a/src/cnetz/fsk_demod.c b/src/cnetz/fsk_demod.c
index 5996038..3164217 100644
--- a/src/cnetz/fsk_demod.c
+++ b/src/cnetz/fsk_demod.c
@@ -218,12 +218,12 @@ void fsk_fm_exit(fsk_fm_demod_t *fsk)
 #endif
 }
 
-/* get levels, sync time and jitter from sync sequence or frame data */
-static inline void get_levels(fsk_fm_demod_t *fsk, double *_min, double *_max, double *_avg, int *_probes, int num, double *_time, double *_jitter)
+/* get levels, sync time and jitter/stddev from sync sequence or frame data */
+static inline void get_levels(fsk_fm_demod_t *fsk, double *_min, double *_max, double *_avg, int *_probes, int num, double *_time, double *_jitter, double *_stddev)
 {
 	int count = 0;
 	double min = 0, max = 0, avg = 0, level;
-	double time = 0, t, sync_average, sync_time, jitter = 0;
+	double time = 0, t, sync_average, sync_time, jitter = 0.0, stddev = 0.0;
 	int bit_offset;
 	int i;
 
@@ -252,6 +252,8 @@ static inline void get_levels(fsk_fm_demod_t *fsk, double *_min, double *_max, d
 		avg += level;
 		count++;
 	}
+	avg /= (double)count;
+	time /= (double)count;
 
 	/* should never happen */
 	if (!count) {
@@ -264,13 +266,13 @@ static inline void get_levels(fsk_fm_demod_t *fsk, double *_min, double *_max, d
 	 * late (positive) we received the sync relative to current bit_time.
 	 * sync_time is the absolute time within the super frame.
 	 */
-	sync_average = time / (double)count;
+	sync_average = time;
 	sync_time = fmod(sync_average + fsk->bit_time + BITS_PER_SUPERFRAME, BITS_PER_SUPERFRAME);
 
 	*_probes = count;
 	*_min = min;
 	*_max = max;
-	*_avg = avg / (double)count;
+	*_avg = avg;
 
 	if (_time) {
 //		if (fsk->cnetz->dsp_mode == DSP_MODE_SPK_V)
@@ -303,6 +305,16 @@ static inline void get_levels(fsk_fm_demod_t *fsk, double *_min, double *_max, d
 		}
 		*_jitter = jitter / (double)count;
 	}
+	if (_stddev) {
+		/* get standard deviation of level */
+		for (i = 0; i < num; i++) {
+			level = fsk->change_levels[(fsk->change_pos - 1 - i) & 0xff];
+			if (level <= 0.0)
+				continue;
+			stddev += (level - avg) * (level - avg);
+		}
+		*_stddev = sqrt(stddev / (double)count);
+	}
 }
 
 static inline void got_bit(fsk_fm_demod_t *fsk, int bit, double change_level)
@@ -348,11 +360,11 @@ got_sync:
 			if (debug)
 				fprintf(fsk->debug_fp, " SYNC!");
 #endif
-			get_levels(fsk, &min, &max, &avg, &probes, 30, &fsk->sync_time, &fsk->sync_jitter);
+			get_levels(fsk, &min, &max, &avg, &probes, 30, &fsk->sync_time, NULL, &fsk->sync_stddev);
 			fsk->sync_level = avg;
 			if (fsk->sync == FSK_SYNC_NEGATIVE)
 				fsk->sync_level = -fsk->sync_level;
-//			printf("sync (change min=%.0f%% max=%.0f%% avg=%.0f%% sync_time=%.2f jitter=%.2f probes=%d)\n", min * 100, max * 100, avg * 100, fsk->sync_time, fsk->sync_jitter, probes);
+//			printf("sync (change min=%.0f%% max=%.0f%% avg=%.0f%% sync_time=%.2f stddev=%.0f%% probes=%d)\n", min * 100, max * 100, avg * 100, fsk->sync_time, fsk->sync_stddev / avg, probes);
 			fsk->level_threshold = (double)avg;
 			fsk->rx_sync = 0;
 			fsk->rx_buffer_count = 0;
@@ -381,7 +393,8 @@ got_sync:
 				/* received 662 bits after start of block (10 SPK blocks + 1 bit (== 2 level changes)) */
 				fsk->sync_time = fmod(fsk->sync_time - (66*10+2) + BITS_PER_SUPERFRAME, BITS_PER_SUPERFRAME);
 			}
-			cnetz_decode_telegramm(fsk->cnetz, fsk->rx_buffer, fsk->sync_level, fsk->sync_time, fsk->sync_jitter);
+			/* receive frame */
+			cnetz_decode_telegramm(fsk->cnetz, fsk->rx_buffer, fsk->sync_level, fsk->sync_time, fsk->sync_stddev);
 		}
 		break;
 	}
@@ -457,7 +470,7 @@ static inline void find_change_slope(fsk_fm_demod_t *fsk)
 		fsk->last_change_positive = change_positive;
 		if (!fsk->sync) {
 			fsk->next_bit = 1.5;
-			got_bit(fsk, change_positive, (level_max - level_min) / 2);
+			got_bit(fsk, change_positive, (level_max - level_min) / 2.0);
 		}
 	}
 	if (fsk->next_bit <= 0.0) {
@@ -530,9 +543,10 @@ static inline void find_change_level(fsk_fm_demod_t *fsk)
 		fsk->last_change_positive = change_positive;
 		if (!fsk->sync) {
 			fsk->next_bit = 1.5;
-			/* if bit change is inside window, we can get level from end of window */
-			s = fsk->bit_buffer_spl[(fsk->bit_buffer_pos + fsk->bit_buffer_len - 1) % fsk->bit_buffer_len];
-			got_bit(fsk, change_positive, fabs(s));
+			/* if bit change is inside window, we can get level from borders of window */
+			s = fsk->bit_buffer_spl[fsk->bit_buffer_pos];
+			s -= fsk->bit_buffer_spl[(fsk->bit_buffer_pos + fsk->bit_buffer_len - 1) % fsk->bit_buffer_len];
+			got_bit(fsk, change_positive, fabs(s / 2.0));
 		}
 	}
 	if (fsk->next_bit <= 0.0) {
diff --git a/src/cnetz/fsk_demod.h b/src/cnetz/fsk_demod.h
index 3410268..addce17 100644
--- a/src/cnetz/fsk_demod.h
+++ b/src/cnetz/fsk_demod.h
@@ -39,7 +39,7 @@ typedef struct fsk_fm_demod {
 	enum fsk_sync	sync;			/* set, if we are in sync and what polarity we receive */
 	double		sync_level;		/* what was the level, when we received the sync */
 	double		sync_time;		/* when did we receive sync, relative to super frame */
-	double		sync_jitter;		/* what was the jitter of the sync */
+	double		sync_stddev;		/* standard deviation of level changes */
 
 	/* speech */
 	sample_t	*speech_buffer;		/* holds one chunk of 12.5ms */
diff --git a/src/cnetz/telegramm.c b/src/cnetz/telegramm.c
index 6c77af2..8b0b539 100644
--- a/src/cnetz/telegramm.c
+++ b/src/cnetz/telegramm.c
@@ -1462,7 +1462,7 @@ static const char *deinterleave(const char *input)
 	return output;
 }
 
-void cnetz_decode_telegramm(cnetz_t *cnetz, const char *bits, double level, double sync_time, double jitter)
+void cnetz_decode_telegramm(cnetz_t *cnetz, const char *bits, double level, double sync_time, double stddev)
 {
 	telegramm_t telegramm;
 	uint8_t opcode;
@@ -1489,12 +1489,11 @@ void cnetz_decode_telegramm(cnetz_t *cnetz, const char *bits, double level, doub
 	opcode = telegramm.opcode;
 	telegramm.level = level;
 	telegramm.sync_time = sync_time;
-	telegramm.jitter = jitter;
 
 	if (bit_errors)
-		PDEBUG_CHAN(DDSP, DEBUG_INFO, "RX Level: %.0f%% Jitter: %.2f Sync Time: %.2f (TS %.2f) Bit errors: %d %s\n", fabs(level) / cnetz->fsk_deviation * 100.0, jitter, sync_time, sync_time / 396.0, bit_errors, (level < 0) ? "NEGATIVE (phone's mode)" : "POSITIVE (base station's mode)");
+		PDEBUG_CHAN(DDSP, DEBUG_INFO, "RX Level: %.0f%% Standard deviation: %.0f%% Sync Time: %.2f (TS %.2f) Bit errors: %d %s\n", fabs(level) / cnetz->fsk_deviation * 100.0, stddev / fabs(level) * 100.0, sync_time, sync_time / 396.0, bit_errors, (level < 0) ? "NEGATIVE (phone's mode)" : "POSITIVE (base station's mode)");
 	else
-		PDEBUG_CHAN(DDSP, DEBUG_INFO, "RX Level: %.0f%% Jitter: %.2f Sync Time: %.2f (TS %.2f) %s\n", fabs(level) / cnetz->fsk_deviation * 100.0, jitter, sync_time, sync_time / 396.0, (level < 0) ? "NEGATIVE (phone's mode)" : "POSITIVE (base station's mode)");
+		PDEBUG_CHAN(DDSP, DEBUG_INFO, "RX Level: %.0f%% Standard deviation: %.0f%% Sync Time: %.2f (TS %.2f) %s\n", fabs(level) / cnetz->fsk_deviation * 100.0, stddev / fabs(level) * 100.0, sync_time, sync_time / 396.0, (level < 0) ? "NEGATIVE (phone's mode)" : "POSITIVE (base station's mode)");
 
 	if (cnetz->sender.loopback) {
 		PDEBUG(DFRAME, DEBUG_NOTICE, "Received Telegramm in loopback test mode (opcode %d = %s)\n", opcode, definition_opcode[opcode].message_name);
diff --git a/src/cnetz/telegramm.h b/src/cnetz/telegramm.h
index bd4ffca..b6bb351 100644
--- a/src/cnetz/telegramm.h
+++ b/src/cnetz/telegramm.h
@@ -61,7 +61,6 @@
 typedef struct telegramm {
 	double level;		/* average level of received sync sequence */
 	double sync_time;	/* when did we receive the sync for this frame */
-	double jitter;		/* phase jitter of sync sequence */
 	uint8_t	opcode;
 	/* used parameters depend on opcode */
 	uint8_t fuz_fuvst_nr;
@@ -124,6 +123,6 @@ int match_fuz(cnetz_t *cnetz, telegramm_t *telegramm, int cell);
 int match_futln(telegramm_t *telegramm, uint8_t futln_nat, uint8_t futln_fuvst, uint16_t futln_rest);
 
 int detect_sync(uint64_t bitstream);
-void cnetz_decode_telegramm(cnetz_t *cnetz, const char *bits, double level, double sync_time, double jitter);
+void cnetz_decode_telegramm(cnetz_t *cnetz, const char *bits, double level, double sync_time, double stddev);
 const char *cnetz_encode_telegramm(cnetz_t *cnetz);