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/avaircraft.h

@@ -188,6 +188,16 @@ namespace BlackMisc
              */
             void setCom2System(const CComSystem &comSystem) { this->m_com2system = comSystem; }
 
+
+            /*!
+             * \brief Is any (COM1/2) active frequency within 8.3383kHz channel?
+             */
+            bool isActiveFrequencyWithin8_33kHzChannel(const BlackMisc::PhysicalQuantities::CFrequency &comFrequency)
+            {
+                return this->m_com1system.isActiveFrequencyWithin8_33kHzChannel(comFrequency) ||
+                       this->m_com2system.isActiveFrequencyWithin8_33kHzChannel(comFrequency);
+            }
+
             /*!
              * \brief Get transponder
              */