Consider Channel Spacing (50, 25, 8.33kHz) for COM frequencies.

Deals with a special topic: While frequencies at VATSIM/flightsim are usually set in 25kHz spacing, some ATC stations (radar) require 8.33kHz tuning.
The now made extension handles this and allows to listen to a voice room even if the corresponding frequency is not exactly tuned in.

Example: EKDK_CTR 135,270 but needs to be tuned in as 135,275

src/blackmisc/avatcstation.h

@@ -10,15 +10,15 @@
 #ifndef BLACKMISC_ATCSTATION_H
 #define BLACKMISC_ATCSTATION_H
 
-#include "valuemap.h"
+#include "vvoiceroom.h"
+#include "aviocomsystem.h"
+#include "avinformationmessage.h"
+#include "avcallsign.h"
+#include "nwuser.h"
+#include "coordinategeodetic.h"
 #include "pqfrequency.h"
 #include "pqlength.h"
 #include "pqtime.h"
-#include "nwuser.h"
-#include "vvoiceroom.h"
-#include "coordinategeodetic.h"
-#include "avcallsign.h"
-#include "avinformationmessage.h"
 #include <QDateTime>
 #include <QMap>
 #include <functional>
@@ -319,6 +319,14 @@ namespace BlackMisc
              */
             bool isBookedNow() const;
 
+            /*!
+             * \brief Tuned in within 25KHz channel spacing
+             */
+            bool isComUnitTunedIn25KHz(const BlackMisc::Aviation::CComSystem &comUnit) const
+            {
+                return comUnit.isActiveFrequencyWithin25kHzChannel(this->getFrequency());
+            }
+
             /*!
              * When booked, 0 means now,
              * negative values mean booking in past,