I never said you could not spot airliners 
But if you get too close to an airliner, somebody is going to be awfully busy filling in some paperwork…
My TCAS is set up to show traffic within 3000ft vertically and in CAS, at altitude, it almost never shows anything. I still see loads of airliners and if say a 747 passes 4000ft below he looks pretty big.
When I had to upgrade my Transponder to Mode S, I choose to install a Trigg TT31 as it is a direct replacement for the trusty KT76A I had. Additionally, I felt it was a good idea to get a bit ahead and get extended squitter with my GNS430. Additionally, the Trigg offering was a lot cheaper than most others at the time.
The first thing I noticed is that I got “Identified” messages upon initial radiocalls while normally squawking VFR 7000 from quite some ATC units in Switzerland and Germany, so they could immediately see my ID and Altitude. Apart, I am able to track my plane if not flown by myself via Flightradar 24 and other such sites. We found out that with the Garmin 430, extended squitter only will work if a flight plan is active.
I do see more small planes with this capability popping up on FR. Certainly it has the advantage that planes like this become visible on anti collision devices which are based on ADS-B.
Recently I did acquire a Power Flarm device, which has proven quite useful. It does show all ADS-B targets quite reliably as well as Mode C targets as a range ring. It is supposed also to show FLARM Targets, which I yet have to encounter.
Generally I believe ADS-B is a good thing to have, simply because it makes you visible to those devices, makes interactions with ATC / FIS a bit more expeditious and, well, it is the future. At least in this case I do see a certain advantage in not waiting until it is mandated…
The first thing I noticed is that I got “Identified” messages upon initial radiocalls while normally squawking VFR 7000 from quite some ATC units in Switzerland and Germany, so they could immediately see my ID and Altitude.
That is standard Mode S and where Mode S is mandatory (e.g. Germany), every airplane is visible like that. I think by now all radar units in Germany have Mode-S display capability.
What exactly is ADS-B used for in Europe?
Currently (almost) only airliners transmit it.
Also beware of the confusion between Elementary Surveillance and Enhanced Surveillance. Both are purely Mode S concepts – nothing to do with ADS-B – and both were invented by Eurocontrol and have no bearing on the equipment actually on the market (which at the time was 100% American). The first one radiates only the tail number, the 24-bit code, and the max airspeed, and you should not have any GPS data going into the GTX330. The second one radiates that, plus whatever else your avionics systems provide in serial digital form to the transponder. There is no configuration for one or the other mode in a GTX330; it is done purely by connecting (or not) the extra data to it.
I am not sure whether there is any practical difference between Enhanced Mode S (where lat/long etc is radiated, which will be the case if a GPS is sending data to it) and ADS-B, in a radar environment where the transponder is interrogated so often that it is radiating the stuff all the time. What exactly is the difference?
This article, despite being very obviously slanted to scare people into buying ADS-B compatible transponders, has a good explanation. It also says UAT ADS-B is US-only, so European ADS-B must be 1090ES which I believe is exactly the same as a Mode S transponder transmits when pinged by radar.
From the Cascade Brochure:
Commission Implementing Regulation No 1207/2011
The Commission Implementing Regulation (EU) No 1207/2011 which was approved and
published in the Official Journal of the European Union in November 2011, includes a
mandate for ADS-B Out. It establishes mandatory carriage and operation of ADS-B 1090 MHz
Extended Squitter by aircraft with a maximum certified take-off mass exceeding 5700kg or
with a maximum cruising true airspeed capability greater than 250 kts when flying IFR/
GAT in European airspace. The compliance dates are January 2015 for forward-fitting and
December 2017 for retrofitting.
This Implementing Regulation will accelerate both the aircraft ADS-B equipage and the
ADS-B ground system deployment.
and both were invented by Eurocontroland
Are you sure? Maybe the terminology is, but much of Mode-S was done by Lincoln Labs of MIT.
European ADS-B must be 1090ES which I believe is exactly the same as a Mode S transponder transmits when pinged by radar.
Uh no. When pinged by radar it usually responds only with the 24bit ICAO address (that should uniquely identify an airframe).
For ADS-B out, it periodically transmits its coordinates in a very peculiar encoding
AIUI, the terms “elementary surveillance” and “enhanced surveillance” are Eurocontrol terms.
Maybe somebody coined them beforehand, but if e.g. you search the GTX330 IM for them, you don’t find them (last time I checked). The GTX330 controls what gets radiated solely by what is wired up to it, and then what is included in the data that are wired up.
There was a more recent firmware update which enables stuff to be disabled from being radiated even though it is connected up and arriving. I don’t know when that came in but it was well after I got mine in 2005. The main use of this was to enable auto GND/AIR mode switching based on GPS GS but without the GPS GS (or GPS anything else) getting radiated. That firmware mod was done by Garmin under European pressure following that daft Eurocontrol position banning the radiation of Enhanced parameters by aircraft that didn’t qualify for Enhanced Mode S (below 250kt, etc) – we had this discussion here before.
The GTX330 basic aircraft config is the aircraft reg (or the flight ID), the 24 bit code, and the speed. AIUI all three get radiated anyway, via the Mode S interrogation. IOW, ATC do not use a database lookup to convert the 24-bit code to the aircraft reg (or the flight ID).
For ADS-B out, it periodically transmits its coordinates in a very peculiar encoding
OK… I thought the ADS-B transmitted packet was more or less the same as the 1090ES transmitted packet, but it got sent autonomously every few secs, instead of needing a radar ping.
However the end result seems to be exactly the same, when one looks at the capabilities of the various plane spotter boxes e.g. Kinetik which can see both kinds of traffic. I know, from a friend, that he can see me flying around, my position, pressure altitude, ground speed, aircraft reg, even though I am definitely “elementary Mode S”, with no GPS data going into the GTX330. If I had GPS data going in, my lat/long would get transmitted precisely but I am not sure it makes any real difference to these boxes (it would to TCAS usage of course, but exactly who has ADS-B-capable TCAS? Definitely not airliners).
Mode S architecture includes both secondary radar interrogation on 1030 MHz with replies on 1090 MHz. The interrogation can also be generated by an a TAS or TCAS unit. The 1090 MHz transmissions are the result of the interrogation. In addition, Mode S supports Squitters on 1090 MHz. A Squitter is a transmission initiated solely by the transponder and is not the result of an interrogation. A mode A/C transponder does not have Squitters. Mode S is different from mode A/C primarily do to its ability to support a unique address. The address is a 24 bit ICAO identifier that is designed to be unique for each aircraft. The ICAO identifiers are assigned in blocks for each state. In the US, the hex values are between A00000 and AFFFFF. In addition, the N number is related to the ICAO ID by an algorithm, essentially a variation of alphabetical order. In other countries, it is up to the state to define how they are assigned and most do it via a database lookup. The basic transmissions are 56 bits in length with a double size message being 112 bits.
Mode S uses a very clever scheme to remain compatible with Mode A/C. On a normal interrogation, there are a series of pulses that are sent and any mode A/C responds accordingly. To avoid invalid responses by transponders from the radar side lobes (90 degrees to the radar antenna direction), one of the pulses is transmitted by the radar via a non directional antenna. As long as the pulse is the same or lesser amplitude than the first pulse, the transponder assumes that it is in the beam and it replies. If the non directional pulse is a greater amplitude, then the transponder assumes it is in the side lobe, and goes to sleep for a fixed amount of time. Mode S fakes the sequence in the main beam to look to Mode A/C transponders that they are in the side lobe and they all go to sleep. The length of the mode S message is limited by how long the Mode A/C transponder is supposed to be asleep.
Squitters are used by the system to let the radar site know that a new mode S aircraft is in the area and should be added to the active scan list. They also let nearby TCAS units know they are nearby and should be queried.
Mode S utilizes various Download Formats, depending on the content of the 1090 MHz transmission. For example DF 4, 5 and 11 are used for replies (Altitude, ID, All call respectively). Other formats can be used for data link capability, etc. Format DF=17 is Extended Squitter and is used by ADS-B. The content of the formats are custom to the function they perform. An ADS-B DF=17 is not a reply and it is what contains the position and other relevant ADS-B data.
The GTX330 basic aircraft config is the aircraft reg (or the flight ID), the 24 bit code, and the speed. AIUI all three get radiated anyway, via the Mode S interrogation. IOW, ATC do not use a database lookup to convert the 24-bit code to the aircraft reg (or the flight ID).
A maximum speed coding is sent (very crude <75, 75 to 150, 150 to 300, 300 to 600, 600 to 1200, greater than 1200 Knots), but speed is not. My understanding is that the ID is either fixed or pilot settable. The latter is used to enter a Flight Number. When the flight number is sent, the Aircraft ID determines the registry number. Aircraft ID is either a 24 bit value in the clear or exclusive or’ed with the parity.
Yes – normally here (light GA) one manually sets the tail number (aircraft reg) and the 24-bit ID. They are not connected in the transponder so you could set them to anything you like. The radiated speed is just the crude range of speeds; yes. The actual speed is not radiated unless one is radiating some subset of “Enhanced” Mode S.
I still don’t know who would possibly make any use of ADS-B here in Europe.
Mode S is already mandated for all IFR in CAS (which is all relevant IFR).
Can my TAS605 display ADS-B targets? Last I heard it was “hardware capable” but not actually capable. But the only people radiating ADS-B are big jets (might be turboprops after 2017) and one will never get anywhere near close to any of these for TCAS purposes to be relevant.
