diff --git a/fleprocess/load_file.go b/fleprocess/load_file.go
index 30d633d..aac90aa 100644
--- a/fleprocess/load_file.go
+++ b/fleprocess/load_file.go
@@ -121,6 +121,11 @@ func LoadFile(inputFilename string, isInterpolateTime bool) (filleFullLog []LogL
 
 		//My Call
 		if regexpHeaderMyCall.MatchString(eachline) {
+			//Attempt to redefine value
+			if headerMyCall != "" {
+				errorLog = append(errorLog, fmt.Sprintf("Attempt to redefine MyCall at line %d", lineCount))
+				continue
+			}
 			errorMsg := ""
 			myCallList := regexpHeaderMyCall.Split(eachline, -1)
 			if len(strings.TrimSpace(myCallList[1])) > 0 {
@@ -136,6 +141,11 @@ func LoadFile(inputFilename string, isInterpolateTime bool) (filleFullLog []LogL
 
 		//Operator
 		if regexpHeaderOperator.MatchString(eachline) {
+			//Attempt to redefine value
+			if headerOperator != "" {
+				errorLog = append(errorLog, fmt.Sprintf("Attempt to redefine Operator at line %d", lineCount))
+				continue
+			}
 			errorMsg := ""
 			myOperatorList := regexpHeaderOperator.Split(eachline, -1)
 			if len(strings.TrimSpace(myOperatorList[1])) > 0 {
@@ -151,6 +161,11 @@ func LoadFile(inputFilename string, isInterpolateTime bool) (filleFullLog []LogL
 
 		// My WWFF
 		if regexpHeaderMyWwff.MatchString(eachline) {
+			//Attempt to redefine value
+			if headerMyWWFF != "" {
+				errorLog = append(errorLog, fmt.Sprintf("Attempt to redefine MyWWFF at line %d", lineCount))
+				continue
+			}
 			errorMsg := ""
 			myWwffList := regexpHeaderMyWwff.Split(eachline, -1)
 			if len(strings.TrimSpace(myWwffList[1])) > 0 {
@@ -166,6 +181,11 @@ func LoadFile(inputFilename string, isInterpolateTime bool) (filleFullLog []LogL
 
 		//My Sota
 		if regexpHeaderMySota.MatchString(eachline) {
+			//Attempt to redefine value
+			if headerMySOTA != "" {
+				errorLog = append(errorLog, fmt.Sprintf("Attempt to redefine MySOTA at line %d", lineCount))
+				continue
+			}
 			errorMsg := ""
 			mySotaList := regexpHeaderMySota.Split(eachline, -1)
 			if len(strings.TrimSpace(mySotaList[1])) > 0 {
@@ -181,6 +201,11 @@ func LoadFile(inputFilename string, isInterpolateTime bool) (filleFullLog []LogL
 
 		//My Grid
 		if regexpHeaderMyGrid.MatchString(eachline) {
+			//Attempt to redefine value
+			if headerMyGrid != "" {
+				errorLog = append(errorLog, fmt.Sprintf("Attempt to redefine MyGrid at line %d", lineCount))
+				continue
+			}
 			errorMsg := ""
 			myGridList := regexpHeaderMyGrid.Split(eachline, -1)
 			if len(strings.TrimSpace(myGridList[1])) > 0 {
@@ -207,6 +232,11 @@ func LoadFile(inputFilename string, isInterpolateTime bool) (filleFullLog []LogL
 
 		//Nickname
 		if regexpHeaderNickname.MatchString(eachline) {
+			//Attempt to redefine value
+			if headerNickname != "" {
+				errorLog = append(errorLog, fmt.Sprintf("Attempt to redefine eQSL Nickname at line %d", lineCount))
+				continue
+			}
 			myNicknameList := regexpHeaderNickname.Split(eachline, -1)
 			if len(strings.TrimSpace(myNicknameList[1])) > 0 {
 				headerNickname = strings.TrimSpace(myNicknameList[1])
@@ -216,43 +246,6 @@ func LoadFile(inputFilename string, isInterpolateTime bool) (filleFullLog []LogL
 			continue
 		}
 
-		// // Date with keyword
-		// if regexpHeaderDateMarker.MatchString(eachline) {
-		// 	errorMsg := ""
-		// 	myDateList := regexpHeaderDateMarker.Split(eachline, -1)
-		// 	if len(myDateList[1]) > 0 {
-		// 		normalizedDate := ""
-		// 		normalizedDate, errorMsg = NormalizeDate(myDateList[1])
-		// 		if len(errorMsg) != 0 {
-		// 			errorLog = append(errorLog, fmt.Sprintf("Invalid Date at line %d: %s (%s)", lineCount, eachline, errorMsg))
-		// 		} else {
-		// 			headerDate, errorMsg = ValidateDate(normalizedDate)
-		// 			if len(errorMsg) != 0 {
-		// 				errorLog = append(errorLog, fmt.Sprintf("Invalid Date at line %d: %s (%s)", lineCount, myDateList[1], errorMsg))
-		// 			}
-		// 		}
-		// 	}
-		// 	//If there is no data after the marker, we just skip the data.
-		// 	continue
-		// }
-
-		// //Date, apparently alone on a line?
-		// if regexpDatePattern.MatchString(eachline) {
-		// 	//We probably have a date, let's normalize it
-		// 	errorMsg := ""
-		// 	normalizedDate := ""
-		// 	normalizedDate, errorMsg = NormalizeDate(eachline)
-		// 	if len(errorMsg) != 0 {
-		// 		errorLog = append(errorLog, fmt.Sprintf("Invalid Date at line %d: %s (%s)", lineCount, eachline, errorMsg))
-		// 	} else {
-		// 		headerDate, errorMsg = ValidateDate(normalizedDate)
-		// 		if len(errorMsg) != 0 {
-		// 			errorLog = append(errorLog, fmt.Sprintf("Invalid Date at line %d: %s (%s)", lineCount, eachline, errorMsg))
-		// 		}
-		// 	}
-		// 	continue
-		// }
-
 		// ****
 		// ** Process the data block
 		// ****
diff --git a/fleprocess/load_file_test.go b/fleprocess/load_file_test.go
index 831bf68..4d2b48a 100644
--- a/fleprocess/load_file_test.go
+++ b/fleprocess/load_file_test.go
@@ -381,6 +381,248 @@ func TestLoadFile_happyCase_day(t *testing.T) {
 	os.Remove(temporaryDataFileName)
 }
 
+func TestLoadFile_redefining_myCall_must_fail(t *testing.T) {
+
+	//Given
+	dataArray := make([]string, 0)
+	dataArray = append(dataArray, "# Header")
+	dataArray = append(dataArray, "myCall on4kjm/p")
+	dataArray = append(dataArray, "operator on4kjm")
+	dataArray = append(dataArray, "nickname Portable")
+	dataArray = append(dataArray, " ")
+	dataArray = append(dataArray, " #Log")
+	dataArray = append(dataArray, "20/5/23")
+	dataArray = append(dataArray, "40m cw 0950 ik5zve/5 9 5")
+	dataArray = append(dataArray, "myCall on4do")
+
+
+
+	temporaryDataFileName := createTestFile(dataArray)
+
+	//When
+	loadedLogFile, isLoadedOK := LoadFile(temporaryDataFileName, true)
+
+	//Then
+	if isLoadedOK {
+		t.Error("Test file processing should return with an error")
+	}
+	if len(loadedLogFile) == 0 {
+		t.Error("No data loaded")
+	}
+
+	expectedValue := "ON4KJM/P"
+	if loadedLogFile[0].MyCall != expectedValue {
+		t.Errorf("Not the expected MyCall value: %s (expecting %s)", loadedLogFile[0].MyCall, expectedValue)
+	}
+
+	//Clean Up
+	os.Remove(temporaryDataFileName)
+}
+
+func TestLoadFile_redefining_myWWFF_must_fail(t *testing.T) {
+
+	//Given
+	dataArray := make([]string, 0)
+	dataArray = append(dataArray, "# Header")
+	dataArray = append(dataArray, "myCall on4kjm/p")
+	dataArray = append(dataArray, "operator on4kjm")
+	dataArray = append(dataArray, "nickname Portable")
+	dataArray = append(dataArray, "myWwff onff-0258")
+	dataArray = append(dataArray, "mySota on/on-001")
+	dataArray = append(dataArray, " ")
+	dataArray = append(dataArray, " #Log")
+	dataArray = append(dataArray, "20/5/23")
+	dataArray = append(dataArray, "40m cw 0950 ik5zve/5 9 5")
+	dataArray = append(dataArray, "myWWFF onff-0001")
+
+
+
+	temporaryDataFileName := createTestFile(dataArray)
+
+	//When
+	loadedLogFile, isLoadedOK := LoadFile(temporaryDataFileName, true)
+
+	//Then
+	if isLoadedOK {
+		t.Error("Test file processing should return with an error")
+	}
+	if len(loadedLogFile) == 0 {
+		t.Error("No data loaded")
+	}
+
+	expectedValue := "ONFF-0258"
+	if loadedLogFile[0].MyWWFF != expectedValue {
+		t.Errorf("Not the expected MyWWFF value: %s (expecting %s)", loadedLogFile[0].MyWWFF, expectedValue)
+	}
+
+	//Clean Up
+	os.Remove(temporaryDataFileName)
+}
+
+func TestLoadFile_redefining_mySOTA_must_fail(t *testing.T) {
+
+	//Given
+	dataArray := make([]string, 0)
+	dataArray = append(dataArray, "# Header")
+	dataArray = append(dataArray, "myCall on4kjm/p")
+	dataArray = append(dataArray, "operator on4kjm")
+	dataArray = append(dataArray, "nickname Portable")
+	dataArray = append(dataArray, "myWwff onff-0258")
+	dataArray = append(dataArray, "mySota on/on-001")
+	dataArray = append(dataArray, " ")
+	dataArray = append(dataArray, " #Log")
+	dataArray = append(dataArray, "20/5/23")
+	dataArray = append(dataArray, "40m cw 0950 ik5zve/5 9 5")
+	dataArray = append(dataArray, "mySota on/on-111")
+
+
+
+	temporaryDataFileName := createTestFile(dataArray)
+
+	//When
+	loadedLogFile, isLoadedOK := LoadFile(temporaryDataFileName, true)
+
+	//Then
+	if isLoadedOK {
+		t.Error("Test file processing should return with an error")
+	}
+	if len(loadedLogFile) == 0 {
+		t.Error("No data loaded")
+	}
+
+	expectedValue := "ON/ON-001"
+	if loadedLogFile[0].MySOTA != expectedValue {
+		t.Errorf("Not the expected MySOTA value: %s (expecting %s)", loadedLogFile[0].MySOTA, expectedValue)
+	}
+
+	//Clean Up
+	os.Remove(temporaryDataFileName)
+}
+
+func TestLoadFile_redefining_myGRID_must_fail(t *testing.T) {
+
+	//Given
+	dataArray := make([]string, 0)
+	dataArray = append(dataArray, "# Header")
+	dataArray = append(dataArray, "myCall on4kjm/p")
+	dataArray = append(dataArray, "operator on4kjm")
+	dataArray = append(dataArray, "nickname Portable")
+	dataArray = append(dataArray, "myWwff onff-0258")
+	dataArray = append(dataArray, "mySota on/on-001")
+	dataArray = append(dataArray, "myGrid YO50")
+	dataArray = append(dataArray, " ")
+	dataArray = append(dataArray, " #Log")
+	dataArray = append(dataArray, "20/5/23")
+	dataArray = append(dataArray, "40m cw 0950 ik5zve/5 9 5")
+	dataArray = append(dataArray, "myGrid ZZ99")
+
+
+
+	temporaryDataFileName := createTestFile(dataArray)
+
+	//When
+	loadedLogFile, isLoadedOK := LoadFile(temporaryDataFileName, true)
+
+	//Then
+	if isLoadedOK {
+		t.Error("Test file processing should return with an error")
+	}
+	if len(loadedLogFile) == 0 {
+		t.Error("No data loaded")
+	}
+
+	expectedValue := "YO50"
+	if loadedLogFile[0].MyGrid != expectedValue {
+		t.Errorf("Not the expected MyGRID value: %s (expecting %s)", loadedLogFile[0].MyGrid, expectedValue)
+	}
+
+	//Clean Up
+	os.Remove(temporaryDataFileName)
+}
+
+
+
+func TestLoadFile_redefining_operator_must_fail(t *testing.T) {
+
+	//Given
+	dataArray := make([]string, 0)
+	dataArray = append(dataArray, "# Header")
+	dataArray = append(dataArray, "myCall on4kjm/p")
+	dataArray = append(dataArray, "operator on4kjm")
+	dataArray = append(dataArray, "nickname Portable")
+	dataArray = append(dataArray, "myWwff onff-0258")
+	dataArray = append(dataArray, "mySota on/on-001")
+	dataArray = append(dataArray, " ")
+	dataArray = append(dataArray, " #Log")
+	dataArray = append(dataArray, "20/5/23")
+	dataArray = append(dataArray, "40m cw 0950 ik5zve/5 9 5")
+	dataArray = append(dataArray, "operator blahh")
+
+
+
+	temporaryDataFileName := createTestFile(dataArray)
+
+	//When
+	loadedLogFile, isLoadedOK := LoadFile(temporaryDataFileName, true)
+
+	//Then
+	if isLoadedOK {
+		t.Error("Test file processing should return with an error")
+	}
+	if len(loadedLogFile) == 0 {
+		t.Error("No data loaded")
+	}
+
+	expectedValue := "ON4KJM"
+	if loadedLogFile[0].Operator != expectedValue {
+		t.Errorf("Not the expected operator value: %s (expecting %s)", loadedLogFile[0].Operator, expectedValue)
+	}
+
+	//Clean Up
+	os.Remove(temporaryDataFileName)
+}
+
+
+func TestLoadFile_redefining_nickname_must_fail(t *testing.T) {
+
+	//Given
+	dataArray := make([]string, 0)
+	dataArray = append(dataArray, "# Header")
+	dataArray = append(dataArray, "myCall on4kjm/p")
+	dataArray = append(dataArray, "operator on4kjm")
+	dataArray = append(dataArray, "nickname Portable")
+	dataArray = append(dataArray, "myWwff onff-0258")
+	dataArray = append(dataArray, "mySota on/on-001")
+	dataArray = append(dataArray, " ")
+	dataArray = append(dataArray, " #Log")
+	dataArray = append(dataArray, "20/5/23")
+	dataArray = append(dataArray, "40m cw 0950 ik5zve/5 9 5")
+	dataArray = append(dataArray, "nickname blaaahh")
+
+
+
+	temporaryDataFileName := createTestFile(dataArray)
+
+	//When
+	loadedLogFile, isLoadedOK := LoadFile(temporaryDataFileName, true)
+
+	//Then
+	if isLoadedOK {
+		t.Error("Test file processing should return with an error")
+	}
+	if len(loadedLogFile) == 0 {
+		t.Error("No data loaded")
+	}
+
+	expectedValue := "Portable"
+	if loadedLogFile[0].Nickname != expectedValue {
+		t.Errorf("Not the expected Nickname value: %s (expecting %s)", loadedLogFile[0].Nickname, expectedValue)
+	}
+
+	//Clean Up
+	os.Remove(temporaryDataFileName)
+}
+
 func TestLoadFile_bad_date(t *testing.T) {
 
 	//Given