Nav Tacan Bw ppt

7/28/2019 Nav Tacan Bw ppt

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TACAN(TACTICAL NAVIGATION SYSTEM)

General:

TACAN is a military system combining the bearing capabilityof VOR with the distance measuring capability of DME

It is also designed to be transportable so that it can be used incombat areas, hence the name tactical


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TACAN(TACTICAL NAVIGATION SYSTEM)

Principle:

TACAN is based on DME in that it uses the DME antenna andthe DME pulse format.

Thus the distance measuring is inherent


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TACANBearing Function:

Two concentric drums are placed around the DME antenna

The parasitic elements distort the DME antenna pattern

The drum structure is rotated at 900 rpm (15 Hz)


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TACANBearing Function:

The resulting pattern has one main lobe caused by theinner parasitic element, and 9 secondary lobes caused

by the outer elements


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TACANAntenna Installation


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TACAN

Thus the TACAN signal consists of 2700 pulse-pairs/secondwhose amplitude is modulated by a 15Hz signal and a 135 Hzsignal

These constitute the variable part of the TACAN signal


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TACAN

The reference part of the TACAN signal consists of coded setsof pulses called reference groups (or bursts)

The MAIN reference group (MRG) consists of 24 pulses withalternate spacings of 12 and 18 s. This is transmitted when theantenna pattern main lobe reference point passes the Northreference

The AUXILIARY reference group (ARG) consists of 12 pulseswith of 30 s spacing. This is transmitted when each of theauxiliary lobe reference points passes the North reference


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TACANThe lobe reference point is the

NEGATIVE-GOING ZERO CROSSOVER


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TACAN RECEIVER


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TACANSince TACAN is not a civilian system it does nothave to conform to normal aviation requirements

However, since military aircraft use the same airway

structure as civilian aircraft, there are TACANScollocated with VORs on most airways. and theseconform with the civilian standards for VORs

These facilities are called VORTACs


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TACAN

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Nav Tacan Bw ppt