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Aircraft Data Decoding A forum to discuss decoding the various data transmissions such as ACARS, Mode-S, ADS-B, etc.

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Old 04-07-2005, 10:13 AM
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Default Software for decoding of Mode S ATC transponders?

Does someone know about a software to decode Elementary and Enhanced Mode S and Extended Squitter transmissions from the aircrafts ATC transponders on 1090 MHz?

Some background information:
The EUROCONTROL ATM 2000+ Strategy confirmed Enhanced Surveillance as essential to safely enable additional traffic growth. Therefore, in the face of continuing traffic growth, Mode S Enhanced Surveillance is planned for deployment in France, Germany and the United Kingdom. The foreseen mandate is March 2005, with a transition period until March 2007.

Enhanced Surveillance through the ground acquisition of specific aircraft parameters will enable the Controllers to increase their efficiency in tactically separating aircraft. The Controller's information is improved by providing actual aircraft derived data such as Magnetic Heading, Air Speed, Selected Altitude and Vertical Rate enabling to reduce the radio telephony (RT) workload and better assess the separation situations. Enhanced Surveillance enables Monitoring Tools and Safety Nets which work on actual data to be implemented or improved (MSAW, STCA) which in turn will allow safety levels to be maintained or improved despite the increase in traffic levels.

Mode S Enhanced Surveillance will entail the use of eight Downlink Aircraft Parameters (DAPs) for initial implementation and these are:

Downlink Aircraft Parameters

Magnetic Heading
Air Speed

Selected Altitude
Vertical Rate

Track Angle Rate
Roll Angle

Ground Speed
True Track Angle


Benefits

The implementation of Mode S Enhanced Surveillance will supports the following benefits:

Operational Improvements

The implementation of Mode S Enhanced Surveillance will supports the following operational improvements:
Automatic Provision of Airborne Derived Data to Enhance Ground Systems Functions including Surveillance
Use of Data Link to improve Efficiency of Communications
Use Aircraft Derived Data for Ground Based Safety Nets
Enhance ATC Decision Support by using Aircraft Derived Data
Maintain and improve the quality of surveillance

Safety Benefits

The safety benefits of Enhanced Surveillance accrue through the improvement of the Controller's situational awareness by:
Reduction in risk of communication error
Improvement of safety by provision of a more precise prediction of horizontal and vertical aircraft behaviour (i.e. monitoring of altitude changes and the execution of altitude clearances)
Improvement of safety in high density traffic areas through increased situational awareness

Capacity Benefits

Reduction of both Controller and Aircrew workload

Reduction of voice channel occupancy

Improvement of the capacity of pre-regulation (e.g. sequencing) in terminal sectors

Reduction of the Controller workload by reducing uncertainty concerning expected behaviour of the aircraft

Improvement of efficiency by allowing for more anticipation in planning of traffic



Read more about Elementary and Enhanced ATC Surveilance Mode S Transponders here: http://www.eurocontrol.int/mode_s/

Just think about how fun it would be to have a program which can decode this information and display it on our computer!

Programmers please have a look at these files:

Principles of Mode S Operations and Interrogator Codes
http://www.eurocontrol.int/mode_s/Do...0Codes%202.pdf
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Old 04-07-2005, 10:32 AM
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http://www.radioreference.com/module...ic&t=21042
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Old 04-07-2005, 10:41 AM
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I missed that tread.
Enhanced Mode S is mandatory in Europe from March 31 2005, so a software for decoding of these transmissions would be highly appreciated.
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Old 04-13-2005, 9:33 AM
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... Also in the LINK2000+ project, data link ATN/VDLM2, listen to 136.975 in Northern Europe for example!

Is the mode S the same as VDLM2?
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Old 04-13-2005, 11:13 PM
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VDLM2 appears to be another form of ACARS

http://www.arinc.com/products/voice_...omm/vdlm2.html

Also, I don't know sound cards but are they able to decode Pulse postion modulation and then quickly change over to PSK. I know that anything I have decoded with a computer was only one or the other, but I guess if it can do both it is just a matter of programing it. I would love to know.
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Old 04-14-2005, 3:10 AM
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VDL Mode 2 and VDL Mode 4 is not a new form for ACARS, but both formats have can be set up for ACARS and ADS-B services, as well as Ground <--> Air communications.

Mode S is not the same as VDL Mode 2, but both can be used for ADS-B.
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Old 04-14-2005, 12:31 PM
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Read the ARINC Link
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Old 04-15-2005, 1:52 AM
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I have been involved in the NEAN and NUP programs (http://www.nup.nu/) so I'm well aware of what VDL mode 2 and VDL Mode 4 is.
And VDL Mode 2 is not ACARS, but includes functionality simular to that of ACARS as well as a lot more.
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Old 04-25-2005, 7:44 PM
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I'm getting into this topic very late in the game, but has anyone ever designed hardware/software so that just the squawk code could be decoded? [I understand the reply depends on how it is interogated, just to save someone from writing that up.]

I've looked at the timing involved and I just can't see how it could be doen with a soundcard or even slicer.
http://mit.edu/6.933/www/Fall2000/mode-s/signal.html

There is better documentation on the transponder coding on the net, though I can't find it again at the moment. What I haven't seen spelled out is the exact modulation scheme. That is, is this OOK (on/off keying), FSK, etc.
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Old 04-25-2005, 10:45 PM
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It seems to be OOK. One of my text books describes it as Pulse Amplitude Modulation.

The same book shows the basic design of transponder decoder for interogations, but I am sure it could be easily modified to decode replies. It is basically a shift register with a 4 MHZ clock input and some NAND gates.

If you like I can scan these pics when I get my printer/scanner working.

Don't know what a slicer is, so I hope I didn't just describe it above.
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Old 04-26-2005, 8:10 AM
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Quote:
Originally Posted by jetmech96
Don't know what a slicer is, so I hope I didn't just describe it above.
a.k.a. a data slicer.

Basically, a radio is discriminator tapped so that the baseband audio can be feed into a data slicer. The data slicer, in turn, converts the audio into one's and zero's so a computer can take it from there.

Feeding baseband audio into a sound card bypasses the data slicer.

http://www.radioreference.com/module...ic&t=13427
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