TCAS decoder anyone...

[majoco]

Hi Guys,

Anyone found an ATCRBS/TCAS/Mode "S" decoder in software yet?

ACARS plots positions nicely but not many domestic aircraft transmit their position data - I only get paints from JetStar, Aerolineas Argentinas and occasionally Emirates here.

All pax aircraft must have TCAS here, so a decoder would (should?) plot all of them within range - admittedly shorter on 1090MHz!

 

[CalebATC]

What are you trying to say?

You have to have the Mode-S/ADS-B box, which is a 1090 MHz radio, along with decoding software.

I believe TCAS use different frequencies too.

 

[majoco]

Caleb said:

I believe TCAS use different frequencies too.

TCAS is an add-on to the ATC SSR transponder. That had various modes that could give info to the ATC operator such as altitude (Mode C) and there were unused Modes that were for 'further developement'. The interrogator is still on 1030MHz and the replies on 1090MHz.

When TCAS was in the development stages, a lot of aircraft were going from dead reckoning and ground-based radio aids to INS and GPS and ultimately a combination of all navigation inputs. (RNAV) It was a comparatively easy job to put the aircraft's position into Mode S. Then all you had to do was to get the transponder to react to interrogation from not only radar but from other aircraft. So the interrogating aircraft sends out his signal via a pair of omni-directional antenna and receives replies from nearby aircraft on another pair of directional "crossed dipoles" antenna. The computer has a heap of information to decode now - altitude, position, bearing, other aircraft's flight number and has to decide if the approaching aircraft is a threat - if so it displays it's position and utlimately advises the pilot of suitable avoiding action. If there is no threat, nothing is displayed. Now we throw EGPWS into the mix and really get complicated!

So all I want to do is receive the aircraft's replies which contain all that data and display the position, altitude and flight number.

Can't be that hard, can it?

Yes, it can!

 

[DaveNF2G]

What data do you need that are not already available from the 4 Mode-S decoder boxes already on the market? If the aircraft has the equipment installed, it transmits ICAO hex code, flight or tail number (manual input), altitude, heading, speed, vertical speed, and transponder code. That's all you need to plot 3D locations on a map, and the decoder boxes have software that does that job for you, too.

 

[majoco]

Kinetis SBS-1 decoder - £500! That's UK pounds - not even US$! Yeah, right