diff --git a/P25Control.cpp b/P25Control.cpp
index d35c26e..eb4c4bf 100644
--- a/P25Control.cpp
+++ b/P25Control.cpp
@@ -432,7 +432,7 @@ bool CP25Control::writeModem(unsigned char* data, unsigned int len)
 				// Build a Group Voice Channel Grant response
 				// Save original LCF and set Grant LCF for encoding
 				unsigned char originalLcf = m_rfData.getLCF();
-				m_rfData.setLCF(P25_LCF_GROUP);
+				m_rfData.setLCF(P25_LCF_GRP_VCH_GRANT);
 				m_rfData.setServiceType(0x00U);  // Service options: 0x00 = routine priority, no emergency
 
 				// Encode TSDU with Grant response
diff --git a/P25Data.cpp b/P25Data.cpp
index 889e45c..2eb72de 100644
--- a/P25Data.cpp
+++ b/P25Data.cpp
@@ -423,12 +423,21 @@ void CP25Data::encodeTSDU(unsigned char* data)
     tsbk[1U] = m_mfId;
 
     switch (m_lcf) {
-		case P25_LCF_GROUP:
+		case P25_LCF_GRP_VCH_GRANT:
+		// Group Voice Channel Grant - format: ServiceOptions(8) + Channel(16) + GroupAddr(16) + SourceAddr(24) = 64 bits
+		// For conventional P25, channel identifier/number is 0 (no trunking)
 		tsbkValue = (unsigned long long)(m_serviceType & 0xFFU);    // Service Options (8 bits)
 		tsbkValue = (tsbkValue << 16) + 0U;                         // Channel ID/Number (16 bits) - 0 for conventional
 		tsbkValue = (tsbkValue << 16) + (m_dstId & 0xFFFFU);        // Group Address (16 bits)
 		tsbkValue = (tsbkValue << 24) + (m_srcId & 0xFFFFFFU);      // Source Radio Address (24 bits)
 		break;
+	    case P25_LCF_GROUP:
+		// Group Voice Channel User - format: Options(16) + GroupAddr(16) + SourceAddr(24) + Reserved(8)
+		tsbkValue = 0U;                                             // Options (16 bits)
+		tsbkValue = (tsbkValue << 16) + (m_dstId & 0xFFFFU);        // Group Address (16 bits)
+		tsbkValue = (tsbkValue << 24) + (m_srcId & 0xFFFFFFU);      // Source Radio Address (24 bits)
+		tsbkValue = (tsbkValue << 8) + 0U;                          // Reserved (8 bits)
+		break;
 	    case P25_LCF_TSBK_CALL_ALERT:
 		tsbkValue = 0U;
 		tsbkValue = (tsbkValue << 16) + 0U;
diff --git a/P25Defines.h b/P25Defines.h
index 7824751..0a25ff7 100644
--- a/P25Defines.h
+++ b/P25Defines.h
@@ -58,6 +58,7 @@ const unsigned int  P25_MI_LENGTH_BYTES = 9U;
 const unsigned char P25_ALGO_UNENCRYPT = 0x80U;
 
 const unsigned char P25_LCF_GROUP   = 0x00U;
+const unsigned char P25_LCF_GRP_VCH_GRANT = 0x02U;
 const unsigned char P25_LCF_PRIVATE = 0x03U;
 
 const unsigned char P25_LCF_TSBK_CALL_ALERT  = 0x1FU;