add alert ADC overload

SpectrumView.pas

@@ -441,7 +441,7 @@ begin
   FTXSpanHz        := 192000.0;
   FTXVfoIndex      := 0;
   FTXOverlay       := False;
-  FADCOverloadVisible := True; // test indicator; later driven by HP Status.
+  FADCOverloadVisible := False;
   FSpectrumBufCount  := 1024;
   FWaterfallBufCount := 1024;
   FWfFrameInterval   := 2;