From e77aafe440aaf8f858c2797c06ce8b130f7231d6 Mon Sep 17 00:00:00 2001
From: David Freese <iam_w1hkj@w1hkj.com>
Date: Sun, 30 Nov 2014 09:19:50 -0600
Subject: [PATCH] MT63 Olivia Peak signal

  * Corrected MT63 and Olivia tx signal generation
    to avoid sound codec overflow
---
 src/mt63/mt63.cxx     | 29 -----------------------------
 src/mt63/mt63base.cxx |  2 +-
 src/olivia/olivia.cxx |  8 +++++---
 src/trx/modem.cxx     |  7 ++-----
 4 files changed, 8 insertions(+), 38 deletions(-)

diff --git a/src/mt63/mt63.cxx b/src/mt63/mt63.cxx
index dc2b5190..28a7b049 100644
--- a/src/mt63/mt63.cxx
+++ b/src/mt63/mt63.cxx
@@ -69,19 +69,12 @@ int mt63::tx_process()
 	guard_lock dsp_lock(&mt63_mutex);
 
 	int c;
-	double maxval = 0;
 
     if (startflag == true) {
         startflag = false;
         if (progdefaults.mt63_usetones) {
-            double maxval = 0.0;
             for (int i = 0; i < (bandwidth * progdefaults.mt63_tone_duration / 96); i++) {
                 Tx->SendTune( progdefaults.mt63_twotones );
-                for (int i = 0; i < Tx->Comb.Output.Len; i++)
-                    if (fabs(Tx->Comb.Output.Data[i]) > maxval)
-                        maxval = fabs(Tx->Comb.Output.Data[i]);
-                for (int i = 0; i < Tx->Comb.Output.Len; i++)
-                    Tx->Comb.Output.Data[i] /= maxval;
                 ModulateXmtr((Tx->Comb.Output.Data), Tx->Comb.Output.Len);
             }
         }
@@ -100,20 +93,9 @@ int mt63::tx_process()
 		stopflag = false;
 		while (--flush) {
 			Tx->SendChar(0);
-			for (int i = 0; i < Tx->Comb.Output.Len; i++)
-				if (fabs(Tx->Comb.Output.Data[i]) > maxval)
-					maxval = fabs(Tx->Comb.Output.Data[i]);
-			for (int i = 0; i < Tx->Comb.Output.Len; i++) {
-				Tx->Comb.Output.Data[i] /= maxval;
-			}
 			ModulateXmtr((Tx->Comb.Output.Data), Tx->Comb.Output.Len);
 		}
 		Tx->SendJam();
-		for (int i = 0; i < Tx->Comb.Output.Len; i++)
-			if (fabs(Tx->Comb.Output.Data[i]) > maxval)
-				maxval = fabs(Tx->Comb.Output.Data[i]);
-		for (int i = 0; i < Tx->Comb.Output.Len; i++)
-			Tx->Comb.Output.Data[i] /= maxval;
 		ModulateXmtr((Tx->Comb.Output.Data), Tx->Comb.Output.Len);
 		cwid();
 		return -1;	/* we're done */
@@ -127,21 +109,10 @@ int mt63::tx_process()
 	if (sendc > 127) {
 		sendc &= 127;
 		Tx->SendChar(127);
-		for (int i = 0; i < Tx->Comb.Output.Len; i++)
-			if (fabs(Tx->Comb.Output.Data[i]) > maxval)
-				maxval = fabs(Tx->Comb.Output.Data[i]);
-		for (int i = 0; i < Tx->Comb.Output.Len; i++)
-			Tx->Comb.Output.Data[i] /= maxval;
 		ModulateXmtr((Tx->Comb.Output.Data), Tx->Comb.Output.Len);
 	}
 
 	Tx->SendChar(sendc);
-	for (int i = 0; i < Tx->Comb.Output.Len; i++)
-		if (fabs(Tx->Comb.Output.Data[i]) > maxval)
-			maxval = fabs(Tx->Comb.Output.Data[i]);
-	for (int i = 0; i < Tx->Comb.Output.Len; i++) {
-		Tx->Comb.Output.Data[i] /= maxval;
-	}
 	ModulateXmtr((Tx->Comb.Output.Data), Tx->Comb.Output.Len);
 
 	put_echo_char(c);
diff --git a/src/mt63/mt63base.cxx b/src/mt63/mt63base.cxx
index da00f6ad..0b402edf 100644
--- a/src/mt63/mt63base.cxx
+++ b/src/mt63/mt63base.cxx
@@ -123,7 +123,7 @@ int MT63tx::Preset(double freq, int BandWidth, int LongInterleave)
 
 	WindowLen = SymbolLen;
 	TxWindow = SymbolShape;
-	TxAmpl = 4.0 / DataCarriers; // for maximum output level we can set TxAmpl=4.0/DataCarriers
+	TxAmpl = 4.0 / DataCarriers; // for maximum undistorted output
 	CarrMarkCode = 0x16918BBEL;
 	CarrMarkAmpl = 0;
 
diff --git a/src/olivia/olivia.cxx b/src/olivia/olivia.cxx
index f63fef8d..79671275 100755
--- a/src/olivia/olivia.cxx
+++ b/src/olivia/olivia.cxx
@@ -119,11 +119,11 @@ void olivia::send_tones()
 
 	preamblephase = 0;
 	for (int i = 0; i < SR4; i++)
-		tonebuff[2*SR4 + i] = tonebuff[i] = nco(freqa) * ampshape[i];
+		tonebuff[2*SR4 + i] = tonebuff[i] = 0.9 * nco(freqa) * ampshape[i];
 
 	preamblephase = 0;
 	for (int i = 0; i < SR4; i++)
-		tonebuff[3*SR4 + i] = tonebuff[SR4 + i] = nco(freqb) * ampshape[i];
+		tonebuff[3*SR4 + i] = tonebuff[SR4 + i] = 0.9 * nco(freqb) * ampshape[i];
 
 	for (int j = 0; j < TONE_DURATION; j += SCBLOCKSIZE)
 		ModulateXmtr(&tonebuff[j], SCBLOCKSIZE);
@@ -208,8 +208,10 @@ int olivia::tx_process()
 	if (c > 0)
 		put_echo_char(c);
 
-	if ((len = Tx->Output(txfbuffer)) > 0)
+	if ((len = Tx->Output(txfbuffer)) > 0) {
+		for (int i = 0; i < len; i++) txfbuffer[i] *= 0.9;
 		ModulateXmtr(txfbuffer, len);
+	}
 
 	if (stopflag && Tx->DoPostambleYet() == 1 && postamblesent != 1) {
 		postamblesent = 1; 
diff --git a/src/trx/modem.cxx b/src/trx/modem.cxx
index f1f13cb0..30cf5360 100644
--- a/src/trx/modem.cxx
+++ b/src/trx/modem.cxx
@@ -455,12 +455,9 @@ void modem::ModulateXmtr(double *buffer, int len)
 
 	if (withnoise && progdefaults.noise) add_noise(buffer, len);
 
-	double mult = pow(10, progdefaults.txlevel / 20.0);
-	for (int i = 0; i < len; i++) {
-		if (buffer[i] < -1.0) buffer[i] = -1.0;
-		if (buffer[i] > 1.0) buffer[i] = 1.0;
+	double mult = 0.98 * pow(10, progdefaults.txlevel / 20.0);
+	for (int i = 0; i < len; i++)
 		buffer[i] *= mult;
-	}
 
 	try {
 		unsigned n = 4;