Friday, 18 September 2015

Very High Frequency VHF

Very High Frequency

VHF Very high frequency (VHF) refers to the 30Mhz to 300MHz band radio waves. Lower than the VHF radio frequency is a high frequency (HF), higher than the VHF radio frequency is UHF (UHF).
Most are used as a VHF radio and television broadcasting, but it is also the aviation and maritime communication channels.

VHF primarily for relatively short-distance transmission, and high-frequency (HF) is different, usually not reflected VHF signal ionosphere, and VHF often affected by environmental factors (such as: topography) on its signal.

VHF omnidirectional range

VHF omnidirectional range (VHF Omni-directional Range, hereinafter referred to as VOR), is a method for aeronautical radio navigation system. Its operating band for the 108.00 MHz -117.95 MHz band is very high, so named. VOR signal transmitted by the transmitter has two: one is fixed phase reference signal; another signal phase angle around the circumference with the beacon is continuously changing, that phase of the signal emitted by each angle is different a. To 360 degrees (pointing to magnetic north) and the reference signal is transmitted in phase (phase difference is 0), and to 180 degrees (pointing to magnetic south pole) transmitted signal with a reference signal phase difference of 180 degrees. VOR receiver on the aircraft according to the phase difference between two signals received can be calculated in the signal itself beacon to which one angle emission. VOR usually rangefinder (DME) with the installation site, in the direction of information supplied to the aircraft, while also providing distance information to aircraft navigation station, the location of such aircraft can be determined only down.