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Automatic Direction Finding

(ADF)

Check the course

guide for references

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Automatic Direction Finding (ADF)

Indicates direction of the selected ground

transmitter from the aircraft

Medium Frequenc !"# $ !% k'D* $ on Directional *eacon (+round

Transmitter)

ADF recei,er on the aircraft

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Components of ADF

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ADF Components

Source:-A,ionics./ Module 0#1 Radio a,igation 2stems/ ational Training Materiels for the Aerospace Industr/

Australian ational Training Authorit/ !""%/ Fig3 !34/ 5age !6!!

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Source:-A,ionics./ Module 0#1 Radio a,igation 2stems/ ational Training Materiels for the Aerospace Industr/

Australian ational Training Authorit/ !""%/ Fig3 !3!7/ 5age !60!

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8oop and 2ense Antenna

Source:-A,ionics./ Module 0#1 Radio a,igation 2stems/ ational Training Materiels for the Aerospace Industr/

Australian ational Training Authorit/ !""%/ Fig3 !3!0/ 5age !6%

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2stems error in ADF

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VOR Very High Frequency Omni-

directional Radio range

Comprising of a ground

beacon and an airborne

installation

!utomatically andcontinuously pro"ides

the operator #ith the

magnetic bearing of the

aircraft from the beacon

VOR ground station

transmits on a specific

frequency bet#een

$%&%% and $$'() *H+,)% H+ channels.

Short range na"igation

system

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VOR purposes:

$Orientation and position fi/ing0

$1racing to or from a VOR ground station0

$holding 2for delaying or manoeu"ringaction30 and

$instrument approaches to land

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9:R Transmitter ;apoints

Source:-A,ionics./ Module 0#1 Radio a,igation 2stems/ ational Training Materiels for the Aerospace Industr/

Australian ational Training Authorit/ !""%/ Fig3 03!/ 5age 067

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9:R 6 Radials

9:R ground transmitter radiates signals in

all directions

74# different tracks a

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Ho# VOR #ors5

$1he VOR ground station transmits t#o VHF

radio signals:

$1he reference phase6 #hich is omni-directional

- 7eamed emission that changes phase as it

rotates cloc#ise lie beam of a light house

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1he aerial of the VOR aircraft recei"er

pics up the signals6 #hose phase

difference 2bet#een the #a"e peas3 ismeasured6 this difference depending on

the bearing of the aeroplane from the

ground station

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8ight House analogy

$9magining a light house emits an

omnidirectional flash of light e"ery time the

beam is pointing due north 9f the speed of

rotation is no#n6 and if a distant obser"er

could record the time inter"al bet#een

seeing omni-directional flash and seeing the

beam6 bearing of the light house can becalculated

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9:R 2ignals

1he demodulated output of the recei"er

contains:

$$%% H+ !udio signal$a Variable phase ;% H+ signal

$a Reference ;% H+ signal in the form of

frequency modulation on a ((

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Source:-A,ionics./ Module 0#1 Radio a,igation 2stems/ ational Training Materiels for the Aerospace Industr/

Australian ational Training Authorit/ !""%/ Fig3 03%/ 5age 06!#

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Source:-A,ionics./ Module 0#1 Radio a,igation 2stems/ ational Training Materiels for the Aerospace Industr/

Australian ational Training Authorit/ !""%/ Fig3 03!&/ 5age 06!>

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VOR 9ndicators

1he output of VOR recei"er:$ !udio to headsets,$%% H+.

$ 7earing information

$ =e"iation from selected radial$ 1O>FRO* signal$ Flag or #arning signal

*anual VOR requires the pilot to select a

particular radial on #hich he #ants to positionhis aircraft 1he actual radial on #hich theaircraft is flying is compared #ith the desiredradial

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Reference

The Air 5ilot?s Manual $ Radio a,igation

and Instrument Fling@ 9ol &/ Tre,or Thom

-A,ionics./ Module 0#1 Radio a,igation

2stems/ ational Training Materiels for theAerospace Industr/ Australian ational

Training Authorit/ !""%/ Fig3 !34/ 5age !6!!