Why ANT?
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Why ANT?
In most planes equipped with an ADF the standard selector switches are BFO, ANT and ADF. What is the use in selecting ANT? . .ANT should only activate the sense antenna, and therefore put the loop antenna "offline". What is the practical sense behind this? Does it have to with different NDB classes (A1A etc.)? Do Transport Cat. airplanes have an ANT switch as well?
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If I recall correctly, the ANT setting is used to improve aural reception; anything from assisting in morse identing to listening to a radio station (only for "operational" reasons of course.....)
The ANT setting does not feature on the Airbus.
rgds
The ANT setting does not feature on the Airbus.
rgds
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As mcdude was eluding to ANT is operationally useful when VHF comms are unavailable and you need to listen to voice transmitting navids in an comms failure emergency, or of you are after ATIS, cricket score etc.
In smaller aircraft to test the ADF, ANT mode is used to displace the needle, then placing it back … you know the rest, people use it when a test mode is not available. ANT does feature on transport CAT A/C, depends on the vintage.
. .The Airbus automatically decodes (and tunes) most navaids for you and displays the ident on the screen, it constantly monitors the ident so tune, identify, test, monitor is achieved visually not aurally. They do have Beat Frequency Oscillator (BFO) option, and you can listen to the ADF for operational reasons (like obtaining the cricket score to satisfy a passengers request) by using voice, but its nice as it filters out the morse code for you so you can get a nice clear ATIS message, it does nothing to the needle display like smaller a/c.
Z
In smaller aircraft to test the ADF, ANT mode is used to displace the needle, then placing it back … you know the rest, people use it when a test mode is not available. ANT does feature on transport CAT A/C, depends on the vintage.
. .The Airbus automatically decodes (and tunes) most navaids for you and displays the ident on the screen, it constantly monitors the ident so tune, identify, test, monitor is achieved visually not aurally. They do have Beat Frequency Oscillator (BFO) option, and you can listen to the ADF for operational reasons (like obtaining the cricket score to satisfy a passengers request) by using voice, but its nice as it filters out the morse code for you so you can get a nice clear ATIS message, it does nothing to the needle display like smaller a/c.
Z
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The REAL reason for ANT mode was to enable MANUAL DF with those sets that had rotating loops, either electronic or manual.. .Flew B707's years ago with this feature...and it was REQUIRED for the type rating (IR) on this aircraft (if equipment was fitted) at one time. . .The younger guys could never see the reason for this....but hey, what do the young guys know anyway?. .Some in AirBus aircraft have a hard time finding the end of the runway ....without the pictorial display, never mind ADF.... <img src="eek.gif" border="0">
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As I recall (from the dim, dark past), selecting ANT will park the pointer on some aircraft (sometimes useful if you have a faulty antenna and the ADF pointer is wandering aimlessly around the dial distracting the hell out of you).
On aircraft with MCDU tuning of ADF's you may be able to select "ANT" by typing "A" after the frequency.
Rgds.. .Q.
P.S. By the way, "411A", didn't the 707's have a LOOP selection also(Can't quite remember what its funtion was tho').
On aircraft with MCDU tuning of ADF's you may be able to select "ANT" by typing "A" after the frequency.
Rgds.. .Q.
P.S. By the way, "411A", didn't the 707's have a LOOP selection also(Can't quite remember what its funtion was tho').
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QAVIAN...yes you are correct, but many had ANT only for the required function...depended on the airline/equipment specified.. .This was a really neat exercise...as was the four course LF radio range...and it worked!. .Sadly....many of the newer guys will never have the chance.
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In the days of old when knights were ........
The ADF had several mode selection positions, OFF, ADF, ANT, LOOP, BFO.
ADF - does what it says on the tin. Automatic Direction Finding.
ANT - enabled only the sense ANTenna thus removing the annoying beat interference that the loop induced and allowing clearer beacon identification (or a nice clear signal on radio 4 or whatever)
LOOP - enabled only the loop antenna. which could then be slewed (and on the realy old ADFs it actually did move the loop aerial. On the newer units it did it electricly)
BFO - Introduced a beat note of 1000hz to enable identification of CW only stations.
The old SOP was to identify the beacon first using ANT and then having established it was the right one select ADF (at max beacon range the interference between loop and sense signals could make it difficult to hear the beacon ident). The loop mode was used in the event of a sense aerial failure (remember they used to be a bit of wire on the top or under the a/c. Very handy for drying wet shirts and trousers) and could be used to manually DF the beacon (it would be along a line at which the ident signal could NOT be heard).
From an engineering point of view ANT and LOOP were very useful diagnostic tools as ADF defects can be very difficult trouble-shoot.
Technically the ADF combines both loop and sense signals to determine the direction of a radio beacon. The loop ant determines the line along which the beacon lies and the sense ant 'resolves the ambiguity' (i.e. tels you whether it is in front or behind you) by only pointing in the dirction in which the phase relationship between the two signals is 90 degs.
The ADF had several mode selection positions, OFF, ADF, ANT, LOOP, BFO.
ADF - does what it says on the tin. Automatic Direction Finding.
ANT - enabled only the sense ANTenna thus removing the annoying beat interference that the loop induced and allowing clearer beacon identification (or a nice clear signal on radio 4 or whatever)
LOOP - enabled only the loop antenna. which could then be slewed (and on the realy old ADFs it actually did move the loop aerial. On the newer units it did it electricly)
BFO - Introduced a beat note of 1000hz to enable identification of CW only stations.
The old SOP was to identify the beacon first using ANT and then having established it was the right one select ADF (at max beacon range the interference between loop and sense signals could make it difficult to hear the beacon ident). The loop mode was used in the event of a sense aerial failure (remember they used to be a bit of wire on the top or under the a/c. Very handy for drying wet shirts and trousers) and could be used to manually DF the beacon (it would be along a line at which the ident signal could NOT be heard).
From an engineering point of view ANT and LOOP were very useful diagnostic tools as ADF defects can be very difficult trouble-shoot.
Technically the ADF combines both loop and sense signals to determine the direction of a radio beacon. The loop ant determines the line along which the beacon lies and the sense ant 'resolves the ambiguity' (i.e. tels you whether it is in front or behind you) by only pointing in the dirction in which the phase relationship between the two signals is 90 degs.
