diff --git a/cmd/callsign.go b/cmd/callsign.go
new file mode 100644
index 0000000..0e50f55
--- /dev/null
+++ b/cmd/callsign.go
@@ -0,0 +1,62 @@
+package cmd
+/*
+Copyright © 2020 Jean-Marc Meessen, ON4KJM <on4kjm@gmail.com>
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import (
+	"regexp"
+	"strings"
+)
+
+
+var validCallRegexp = regexp.MustCompile(`[\d]{0,1}[A-Z]{1,2}\d([A-Z]{1,4}|\d{3,3}|\d{1,3}[A-Z])[A-Z]{0,5}`)
+var validPrefixRegexp = regexp.MustCompile(`\A\d?[a-zA-Z]{1,2}$`)
+
+// ValidateCall veriffies whether the supplied string is a valid callsign.
+// prefix and suffix are not checked for validity
+// If it is not valid, the supicious string is prefixed with a * and an erroMsg is genrated.
+func ValidateCall(sign string) (call, errorMsg string) {
+	sign = strings.ToUpper(strings.TrimSpace(sign))
+	sp := strings.Split(sign, "/")
+	wrongSign := "*" + sign
+	switch len(sp) {
+	case 1:
+		if validCallRegexp.MatchString(sign) {
+			return sign, ""
+		} else {
+			return wrongSign, "Invalid call"
+		}
+	case 2:
+		// some ambiguity here we need to resolve, could be a prefix or a suffix
+		if validCallRegexp.MatchString(sp[0]) {
+			//Callisign with suffix (unchecked)
+			return sign, ""
+		} else {
+			//Callsign with prefix
+			//validate the part that should contain the call (sp[1]) 
+			if !validCallRegexp.MatchString(sp[1]) {
+				return wrongSign, "Invalid call"
+			}
+			//validate the prefix
+			if !validPrefixRegexp.MatchString(sp[0]) {
+				return wrongSign, "Invalid prefix"
+			}
+			return sign, ""
+		}
+	case 3:
+		return sign, "??????"
+	}
+	return sign, "?????"
+}
\ No newline at end of file
diff --git a/cmd/load.go b/cmd/load.go
index 14c02c0..3954cb3 100644
--- a/cmd/load.go
+++ b/cmd/load.go
@@ -22,7 +22,7 @@ import (
 	"log"
 	"os"
 	"regexp"
-	"strings"
+	//"strings"
 )
 
 // loadCmd represents the load command
@@ -79,13 +79,16 @@ func loadFile() {
 	regexpStartMultiLineComment, _ := regexp.Compile("^{")
 	regexpEndMultiLineComment, _ := regexp.Compile("}$")
 	regexpHeaderMyCall, _ := regexp.Compile("(?i)^mycall ")
-	// regexpHeaderOperator, _ := regexp.Compile("(?i)^operator ") 
+	regexpHeaderOperator, _ := regexp.Compile("(?i)^operator ") 
 	// regexpHeaderMyWwff, _ := regexp.Compile("(?i)^mywwff ")
 	// regexpHeaderMySota, _ := regexp.Compile("(?i)^mysota ")
 	// regexpHeaderQslMsg, _ := regexp.Compile("(?i)^qslmsg ")
 	// regexpHeaderNickname, _ := regexp.Compile("(?i)^nickname ")
 	// regexpHeaderDate, _ := regexp.Compile("(?i)^date ")
 
+	headerMyCall := ""
+	headerOperator := ""
+
 	var isInMultiLine = false 
 	
  
@@ -125,19 +128,28 @@ func loadFile() {
 		// ****
 
 		if(regexpHeaderMyCall.MatchString(eachline)) {
-			myCallList := regexpHeaderMyCall.Split(eachline,-1)
-			myCall := ""
+			errorMsg := ""
+			myCallList := regexpHeaderMyCall.Split(eachline,-1)			
 			if(len(myCallList[1]) > 0) {
-				myCall = strings.ToUpper(myCallList[1])
+				headerMyCall, errorMsg = ValidateCall(myCallList[1])
 			}
-			fmt.Println("my call: ", myCall)
+			fmt.Println("my call: ", headerMyCall, "-", errorMsg)
 			continue
 		}
 
+		if(regexpHeaderOperator.MatchString(eachline)) {
+			errorMsg := ""
+			myOperatorList := regexpHeaderOperator.Split(eachline,-1)
+			if(len(myOperatorList[1]) > 0) {
+				headerOperator, errorMsg = ValidateCall(myOperatorList[1])
+			}
+			fmt.Println("Operator: ", headerOperator, "-", errorMsg)
+			continue
+		}
 		// ****
 		// ** Process the data block
 		// ****
 
 		fmt.Println(eachline)
 	}
-}
\ No newline at end of file
+}