diff --git a/HPSDRNetwork.pas b/HPSDRNetwork.pas
index 418f3e7..fa1731b 100644
--- a/HPSDRNetwork.pas
+++ b/HPSDRNetwork.pas
@@ -1134,7 +1134,8 @@ function CalcAlex0(RXFreqHz, TXFreqHz: Double;
                    const Alex: TAlexSettings;
                    XvtrRxAnt: Byte = 0;
                    XvtrUseRxDDCIn: Boolean = False;
-                   XvtrDisablePA: Boolean = False): LongWord;
+                   XvtrDisablePA: Boolean = False;
+                   XvtrActive: Boolean = False): LongWord;
 var
   txf:     Double;
   BandIdx: Integer;
@@ -1237,8 +1238,11 @@ begin
                           or $00000800;   // bit 11: Bypass relay
       2: Result := Result or $00000400    // bit 10: Ext2
                           or $00000800;   // bit 11: Bypass relay
-      3: Result := Result or $00000100    // bit 8:  XVTR DDC In
-                          or $00000800;   // bit 11: Bypass relay
+      // XVTR DDC In только когда трансвертер активен — иначе порт молчит
+      // (аналог Thetis Alex.cs: "do not use XVTR ant port if not using transverter")
+      3: if XvtrActive then
+           Result := Result or $00000100  // bit 8:  XVTR DDC In
+                            or $00000800; // bit 11: Bypass relay
     end;
   end;
 end;
@@ -1405,7 +1409,8 @@ begin
   begin
     Alex0 := CalcAlex0(FCurrentRXFreq, FCurrentTXFreq,
                        FIsTransmitting, IsOrion2, FAlexConfig,
-                       FXvtrRxAntOverride, FXvtrUseRxDDCIn, FXvtrDisablePA);
+                       FXvtrRxAntOverride, FXvtrUseRxDDCIn, FXvtrDisablePA,
+                       FXvtrEnable);
     Buf[1432] := (Alex0 shr 24) and $FF;
     Buf[1433] := (Alex0 shr 16) and $FF;
     Buf[1434] := (Alex0 shr  8) and $FF;