diff --git a/Radio.cpp b/Radio.cpp
index 4eecd931e..c6175634e 100644
--- a/Radio.cpp
+++ b/Radio.cpp
@@ -17,6 +17,10 @@ namespace Radio
     // very loose validation - callsign must contain a letter next to
     // a number
     QRegularExpression valid_callsign_regexp {R"(\d[[:alpha:]]|[[:alpha:]]\d)"};
+
+    // suffixes that are often used and should not be interpreted as a
+    // DXCC Entity prefix used as a suffix
+    QRegularExpression non_prefix_suffix {R"(\A([0-9AMPQR]|QRP|F[DF]|[AM]M|L[HT]|LGT)\z)"};
   }
 
 
@@ -125,6 +129,34 @@ namespace Radio
             callsign = callsign.left (slash_pos);
           }
       }
-    return callsign;
+    return callsign.toUpper ();
+  }
+
+  // analyze the callsign and determine the effective prefix, returns
+  // the full call if no valid prefix (or prefix as a suffix) is specified
+  QString effective_prefix (QString callsign)
+  {
+    auto prefix = callsign.toUpper ();
+    auto slash_pos = callsign.indexOf ('/');
+    if (slash_pos >= 0)
+      {
+        auto right_size = callsign.size () - slash_pos - 1;
+        if (right_size >= slash_pos) // naive call is longer than
+                                     // prefix/suffix algorithm
+          {
+            prefix = callsign.left (slash_pos);
+          }
+        else
+          {
+            prefix = callsign.mid (slash_pos + 1);
+            if (prefix.contains (non_prefix_suffix))
+              {
+                prefix = callsign.left (slash_pos); // ignore
+                                                    // non-prefix
+                                                    // suffixes
+              }
+          }
+      }
+    return prefix;
   }
 }
diff --git a/Radio.hpp b/Radio.hpp
index b8eec22a7..7f8b0a0f4 100644
--- a/Radio.hpp
+++ b/Radio.hpp
@@ -54,6 +54,7 @@ namespace Radio
   bool UDP_EXPORT is_callsign (QString const&);
   bool UDP_EXPORT is_compound_callsign (QString const&);
   QString UDP_EXPORT base_callsign (QString);
+  QString UDP_EXPORT effective_prefix (QString);
 }
 
 Q_DECLARE_METATYPE (Radio::Frequency);
diff --git a/logbook/countrydat.cpp b/logbook/countrydat.cpp
index b66f0664e..d1997a977 100644
--- a/logbook/countrydat.cpp
+++ b/logbook/countrydat.cpp
@@ -19,6 +19,7 @@
 #include <QFile>
 #include <QTextStream>
 #include <QDebug>
+#include "Radio.hpp"
 
 void CountryDat::init(const QString filename)
 {
@@ -131,14 +132,15 @@ QString CountryDat::find(QString call) const
       return fixup (_data.value ("=" + call), call);
     }
 
-  auto prefix = call;
-  while (prefix.size () >= 1)
+  auto prefix = Radio::effective_prefix (call);
+  auto match_candidate = prefix;
+  while (match_candidate.size () >= 1)
     {
-      if (_data.contains (prefix))
+      if (_data.contains (match_candidate))
         {
-          return fixup (_data.value (prefix), call);
+          return fixup (_data.value (match_candidate), prefix);
         }
-      prefix = prefix.left (prefix.size () - 1);
+      match_candidate = match_candidate.left (match_candidate.size () - 1);
     }
   return QString {};
 }
@@ -150,7 +152,7 @@ QString CountryDat::fixup (QString country, QString const& call) const
   //
 
   // KG4 2x1 and 2x3 calls that map to Gitmo are mainland US not Gitmo
-  if (call.startsWith ("KG4") && call.size () != 5)
+  if (call.startsWith ("KG4") && call.size () != 5 && call.size () != 3)
     {
       country.replace ("Guantanamo Bay; KG4; NA", "United States; K; NA");
     }