Please Help - What are NDBs and ADFs
Thread Starter
Joined: Apr 2002
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From: Australia
Please Help - What are NDBs and ADFs
Hey all,
I am an avation enthusiast and I'm 15. I know what VORs are and how the work, but what about ADF's and NDB's? What do they do and how do they work?
Any help would be much appreciated.
Fly High,
GROUND AFFECT
I am an avation enthusiast and I'm 15. I know what VORs are and how the work, but what about ADF's and NDB's? What do they do and how do they work?
Any help would be much appreciated.
Fly High,
GROUND AFFECT
Joined: Apr 2001
Posts: 871
Likes: 0
From: Chichester, UK
NDB - Non-directional beacon. This is a ground-based transmitter like a VOR, but just transmits in all directions. It's either a radio mast or a 'T' arial slung between two masts. It also transmits a morse Identifier, so you know you've got the right one 
ADF - Automatic direction finder. Fitted in the aeroplane, and has a needle that indicates the direction from which the signals of a selected NDB are being received. Also known as a Relative Bearing Indicator (RBI). A more sophisticated version is the Radio Magnetic Indicator (RMI).
The ADF/NDB combination is, I think, the simplest radio nav. combination.
To use them in flight, you just tune the ADF to a given NDB frequency. They're used in conjunction with the heading indicator to track to or from an NDB and to fix the aircraft's position.
ADF - Automatic direction finder. Fitted in the aeroplane, and has a needle that indicates the direction from which the signals of a selected NDB are being received. Also known as a Relative Bearing Indicator (RBI). A more sophisticated version is the Radio Magnetic Indicator (RMI).
The ADF/NDB combination is, I think, the simplest radio nav. combination.
To use them in flight, you just tune the ADF to a given NDB frequency. They're used in conjunction with the heading indicator to track to or from an NDB and to fix the aircraft's position.
Joined: Aug 2000
Posts: 1,214
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From: S Warwickshire
Oh alright then, here gos.
An ADF is an aerial direction finder - you tune to a radio station in the MF or HF frequency bands nad the needle on the indicator will point out the relative bearing of the radio station from the aircraft.
An NDB is an aeronautical radio beacon designed for reception and navigation with an ADF. These are usually homing beacons at airfields or on the approach path.
An ADF is an aerial direction finder - you tune to a radio station in the MF or HF frequency bands nad the needle on the indicator will point out the relative bearing of the radio station from the aircraft.
An NDB is an aeronautical radio beacon designed for reception and navigation with an ADF. These are usually homing beacons at airfields or on the approach path.
Joined: Oct 2000
Posts: 284
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From: UK
NDBs were used in the Maritime Service long before the Aeronautical Service.
Any vertically polarised LF/MF radio transmitter will act as an NDB as the signal in theory, radiates in all directions. The advantage of the NDB for aeronautical use is the cone of silence vertically above the beacon which givies a precise overhead hence their use as airway markers before the VOR. Broadcast stations may also be used but their high power, modulation and variable polarisation can detract from the accuracy.
ADF is "Automatic" DF as opposed to Manual DF that was predominantly used on ships and early aircraft.
Any vertically polarised LF/MF radio transmitter will act as an NDB as the signal in theory, radiates in all directions. The advantage of the NDB for aeronautical use is the cone of silence vertically above the beacon which givies a precise overhead hence their use as airway markers before the VOR. Broadcast stations may also be used but their high power, modulation and variable polarisation can detract from the accuracy.
ADF is "Automatic" DF as opposed to Manual DF that was predominantly used on ships and early aircraft.
Joined: Apr 2001
Posts: 871
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From: Chichester, UK
Just to add, the disadvantage of NDBs is that they are more prone to error than VORs. For example, there are reflections from hills, coastal effects, night effects due to the movement of the ionosphere ... and a thunderstorm pumps out a lot of non-directional energy in the radio band, making it a rather effective NDB
