Add VHF XVTR PA calibration; fix TX drive formula and stale FDriveLevel

PA calibration per band (HF and VHF):
- Add VHFBandCal[0..7] in TGlobalSettings (saved as vhf_cal_0..7 in JSON)
- Default HF cal updated to Thetis HERMES defaults (38.8-41.3 dB per band)
- Default VHF cal = 56.2 dB (Thetis HERMES XVTR default)
- SettingsForm: second group in PA tab "VHF Calibration (Transverters)" with
  8 spinboxes VHF0..VHF7; labels dynamically show XVTR slot ButtonText
  when LoadXvtrSettings is called (e.g. "VHF0 (2m):")

TX drive formula (CalcDriveByte) rewritten to match Thetis exactly:
  drive_byte = min(sqrt(10^((10*log10(pwr_W*1000) - Cal)/10) * 0.05) / 0.8, 1.0) * 1.02 * 255
  Cal = PA gain in dB (not a percentage); matches Thetis verified output
  (Cal=63.1 + slider=100% + PAMax=100W → drive_byte=16, verified against Thetis)
  Old formula Pos/100*Cal/100*255 was wrong: treated dB gain as linear percent

Fix stale FDriveLevel not updated on band/XVTR switch:
- Startup: FCurrentBand must be set before CalcDriveByte (was reversed)
- RestoreBand: recalculate FDriveLevel before ApplyVfoA network update
- ActivateXvtrBand: recalculate after FCurrentXvtr changes
- ApplyVfoA: recalculate when VFO crosses HF band boundary
- FreqDispBChanged: same for VFO-B band changes
- ApplyMOX(True): safety recalculate at PTT engage time

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

MainForm.pas

@@ -209,6 +209,7 @@ type
     FDriveLevel:   Byte;
     FPAMaxPower:   Double;
     FPABandCal:    array[0..BAND_COUNT-1] of Double;  // калибровка 38.8..100.0 на диапазон
+    FVHFBandCal:   array[0..CFG_XVTR_COUNT-1] of Double; // калибровка VHF/XVTR слотов
     FRunning:      Boolean;
     FTransmitting: Boolean;
     FSplitTxB:     Boolean;
@@ -658,6 +659,7 @@ type
     procedure ApplyMOX(Active: Boolean);
     procedure OnTXIQReady(const Buf: array of Double; Count: Integer);
     procedure OnPASettingsChange(MaxPower: Double; const BandCal: array of Double);
+    procedure OnVHFCalSettingsChange(const VHFCal: array of Double);
     procedure OnTXSettingsChange(const T: TTXSettings);
     procedure BtnAGCModeClick(Sender: TObject);
     procedure TrkAGCChange(Sender: TObject);
@@ -947,6 +949,8 @@ begin
   Result.PAMaxPower       := FPAMaxPower;
   for i := 0 to BAND_COUNT - 1 do
     Result.PABandCal[i]   := FPABandCal[i];
+  for i := 0 to CFG_XVTR_COUNT - 1 do
+    Result.VHFBandCal[i]  := FVHFBandCal[i];
   Result.ActiveVfo        := FActiveVfo;
   Result.NRMode           := BtnNR.Tag;
   Result.NBMode           := BtnNB.Tag;
@@ -1118,6 +1122,8 @@ begin
   FVfoB       := B.VfoB;
   FreqDispB.Frequency := Round(FVfoB);
 
+  // Пересчитываем drive byte для нового диапазона перед отправкой в сеть
+  FDriveLevel := CalcDriveByte;
   // ApplyVfoA обновит сеть, FreqDisp, shift, перерисует
   ApplyVfoA(Round(B.VfoA));
 end;
@@ -1157,7 +1163,8 @@ begin
   FSpecDrag  := False;
   FDriveLevel    := 0;
   FPAMaxPower    := 100.0;
-  for i := 0 to BAND_COUNT - 1 do FPABandCal[i] := 100.0;
+  for i := 0 to BAND_COUNT - 1 do FPABandCal[i] := CFG_PA_BAND_CAL_DEFAULT[i];
+  for i := 0 to CFG_XVTR_COUNT - 1 do FVHFBandCal[i] := CFG_VHF_CAL_DEFAULT;
   FRunning       := False;
   FTransmitting  := False;
   FSplitTxB      := False;
@@ -3731,10 +3738,12 @@ begin
   FPAMaxPower  := G_Settings.PAMaxPower;
   for i := 0 to BAND_COUNT - 1 do
     FPABandCal[i] := G_Settings.PABandCal[i];
+  for i := 0 to CFG_XVTR_COUNT - 1 do
+    FVHFBandCal[i] := G_Settings.VHFBandCal[i];
   // Slider position (0..100) and calibrated drive byte
   TrkDrive.Position := EnsureRange(G_Settings.DriveLevel, 0, 100);
-  FDriveLevel  := CalcDriveByte;
   FCurrentBand := G_Settings.LastBand;
+  FDriveLevel  := CalcDriveByte;
   // SampleRate — глобальный, загружаем до RestoreBand
   if G_Settings.SampleRate > 0 then
   begin
@@ -4098,6 +4107,7 @@ begin
       StyleButton(BtnBand[FCurrentBand], False);
       FCurrentBand := BandIdx;
       StyleButton(BtnBand[FCurrentBand], True);
+      FDriveLevel := CalcDriveByte;
     end;
     FSpecView.InvalidateRulerCache;
     SyncSpecViewFreq;
@@ -4297,6 +4307,7 @@ begin
       StyleButton(BtnBand[FCurrentBand], False);
       FCurrentBand := BandIdx;
       StyleButton(BtnBand[FCurrentBand], True);
+      FDriveLevel := CalcDriveByte;
     end;
   end;
 
@@ -5002,6 +5013,7 @@ begin
     Exit;
   WasTransmitting := FTransmitting;
   FTransmitting := Active;
+  if Active then FDriveLevel := CalcDriveByte;
   FDUCPendingCount := 0;
   if FTransmitting then
   begin
@@ -5907,31 +5919,33 @@ begin
 end;
 
 function TMainForm.CalcDriveByte: Byte;
+// Thetis-compatible formula:
+//   drive_byte = int( min(target_volts/0.8, 1.0) * 1.02 * 255 )
+// where:
+//   target_volts = sqrt( 10^((target_dBm)/10) * 0.05 )   [E=sqrt(P*R), R=50, P in mW]
+//   target_dBm   = 10*log10(pwr_W * 1000) - Cal
+//   pwr_W        = Pos/100 * FPAMaxPower
+//   Cal          = per-band PA gain in dB (HF: ~38.8-41.3, VHF default: ~56.2)
 var
-  Cal:        Double;
-  Pos:        Integer;
-  XvtrActive: Boolean;
+  Cal:          Double;
+  Pos:          Integer;
+  XvtrActive:   Boolean;
+  pwr_W:        Double;
+  target_dBm:   Double;
+  target_volts: Double;
+  audio_vol:    Double;
 begin
-  if (FCurrentBand >= 0) and (FCurrentBand < BAND_COUNT) and (FPABandCal[FCurrentBand] > 0.0) then
-    Cal := FPABandCal[FCurrentBand]
-  else
-    Cal := 100.0;
-
   XvtrActive := (FCurrentXvtr >= 0) and (FCurrentXvtr < CFG_XVTR_COUNT) and
                 FXvtrSettings.Entries[FCurrentXvtr].Enabled;
 
-  // Pos — итоговый процент драйва 0..100 ДО per-band калибровки.
-  //
-  // Логика (как в Thetis):
-  //  • Регулярный TX:
-  //      HF   → Pos = TrkDrive.Position
-  //      XVTR → Pos = TrkDrive.Position × (XVTR.TXPower / 100)
-  //             (TXPower работает как верхний предел драйва на трансверторе)
-  //  • TUN (кнопка):
-  //      HF                          → Pos = TUNLevel    (TTXSettings.TUNLevel)
-  //      XVTR, UseXVTRTunePower=False → Pos = TUNLevel    (поведение как HF)
-  //      XVTR, UseXVTRTunePower=True  → Pos = XVTR.TXPower
-  //             (галка ЗАМЕНЯЕТ TUNLevel на XVTR power — Thetis-семантика)
+  if XvtrActive then
+    Cal := FVHFBandCal[FCurrentXvtr]
+  else if (FCurrentBand >= 0) and (FCurrentBand < BAND_COUNT) then
+    Cal := FPABandCal[FCurrentBand]
+  else
+    Cal := 38.8;
+
+  // Pos — итоговый процент драйва 0..100
   if FTuning then
   begin
     if XvtrActive and FXvtrSettings.UseXVTRTunePower then
@@ -5942,13 +5956,18 @@ begin
   else
   begin
     if XvtrActive then
-      Pos := Round(TrkDrive.Position
-                   * FXvtrSettings.Entries[FCurrentXvtr].TXPower / 100.0)
+      Pos := Round(TrkDrive.Position * FXvtrSettings.Entries[FCurrentXvtr].TXPower / 100.0)
     else
       Pos := TrkDrive.Position;
   end;
 
-  Result := Round(Pos / 100.0 * Cal / 100.0 * 255.0);
+  if Pos <= 0 then begin Result := 0; Exit; end;
+
+  pwr_W        := Pos / 100.0 * FPAMaxPower;
+  target_dBm   := 10.0 * Log10(pwr_W * 1000.0) - Cal;
+  target_volts := Sqrt(Power(10.0, target_dBm * 0.1) * 0.05);
+  audio_vol    := Min(target_volts / 0.8, 1.0);
+  Result       := Min(Round(audio_vol * 1.02 * 255.0), 255);
 end;
 
 procedure TMainForm.OnTXIQReady(const Buf: array of Double; Count: Integer);
@@ -6002,6 +6021,21 @@ begin
     FNetwork.UpdateState(XvtrTranslate(FCenterFreq), XvtrTranslate(ActiveTXFreqHz), FDriveLevel, FTransmitting, True, True);
 end;
 
+procedure TMainForm.OnVHFCalSettingsChange(const VHFCal: array of Double);
+var i: Integer;
+begin
+  for i := 0 to CFG_XVTR_COUNT - 1 do
+  begin
+    if i <= High(VHFCal) then
+      FVHFBandCal[i] := VHFCal[i]
+    else
+      FVHFBandCal[i] := CFG_VHF_CAL_DEFAULT;
+  end;
+  FDriveLevel := CalcDriveByte;
+  if FNetwork.Connected and FNetwork.Running then
+    FNetwork.UpdateState(XvtrTranslate(FCenterFreq), XvtrTranslate(ActiveTXFreqHz), FDriveLevel, FTransmitting, True, True);
+end;
+
 procedure TMainForm.OnTXSettingsChange(const T: TTXSettings);
 // Любая правка в Settings→Transmit летит сюда: обновляем FTXSettings,
 // перешиваем WDSP TX-цепь и (если поменялись mic-биты) перепосылаем DUC Specific.
@@ -6097,11 +6131,12 @@ begin
 end;
 
 // Передаёт XVTR-режим в сетевой слой. Вызывается при смене XVTR или его
-// настроек. Управляет XVTR Enable bit, DDC IN routing, T/R relay suppression.
+// настроек. Управляет XVTR Enable bit, T/R relay suppression.
+// XVTR DDC In (Alex bits 8+11) управляется через галочку XVTR в Antenna/Alex
+// tab для IF-диапазона (Alex.RxOnly[IF_band]=3) — аналогично Thetis.
 procedure TMainForm.ApplyXvtrToNetwork;
 var
   En: Boolean;
-  UseDDCIn: Boolean;
   DisablePA: Boolean;
   RxAnt: Byte;
 begin
@@ -6109,16 +6144,15 @@ begin
      FXvtrSettings.Entries[FCurrentXvtr].Enabled then
   begin
     En        := True;
-    UseDDCIn  := True;
     DisablePA := FXvtrSettings.Entries[FCurrentXvtr].DisablePA;
     RxAnt     := FXvtrSettings.Entries[FCurrentXvtr].RXAntenna;
   end
   else
   begin
-    En := False; UseDDCIn := False; DisablePA := False; RxAnt := 0;
+    En := False; DisablePA := False; RxAnt := 0;
   end;
   if FNetwork.Connected then
-    FNetwork.SetXvtrMode(En, UseDDCIn, DisablePA, RxAnt);
+    FNetwork.SetXvtrMode(En, DisablePA, RxAnt);
 end;
 
 // Перестраивает динамические XVTR-кнопки в PanelBands. Удаляет старые,
@@ -6289,9 +6323,8 @@ begin
   FCenterFreq := Vis;
   FreqDispA.Frequency := Round(FVfoA);
   if FWDSPReady then FDSPEngine.SetShift(0.0);
-  // Применяем драйв (если есть кастомный TX power для этого XVTR)
-  // Сделано на стороне ActiveTXFreqHz / TX path — здесь только обновляем дисплей.
-  // Отправляем в сеть с трансляцией
+  // Пересчитываем drive byte для нового XVTR слота и отправляем в сеть
+  FDriveLevel := CalcDriveByte;
   if FNetwork.Connected and FNetwork.Running then
   begin
     FNetwork.UpdateState(XvtrTranslate(FCenterFreq), XvtrTranslate(ActiveTXFreqHz),
@@ -6683,6 +6716,7 @@ begin
     SF.OnVisibilityChange := ApplyVisibility;
     SF.OnFPSChange        := ApplyFPS;
     SF.OnPAChange         := OnPASettingsChange;
+    SF.OnVHFCalChange     := OnVHFCalSettingsChange;
     SF.OnCATChange        := OnCATSettingsChange;
     SF.OnThemeChange           := SetLightTheme;
     SF.OnFreqMhzDigitsChange   := ApplyFreqMhzDigits;
@@ -6699,6 +6733,7 @@ begin
     IfThen(FNetwork.Connected, FNetwork.Device.BoardType, FPendingBoardType));
   SF.LoadXvtrSettings(FXvtrSettings);
   SF.LoadPASettings(FPAMaxPower, FPABandCal);
+  SF.LoadVHFCalSettings(FVHFBandCal);
   SF.LoadCATSettings(
     FCATLastGlobal.CATSerialEnabled,
     FCATLastGlobal.CATSerialPort,