Peter wrote:
and there is no MLAT for Mode A
Why not?
Actually you are right; there is still a squawk being returned. I just haven’t seen Mode A contacts on the tracking sites.
This wording of the proposal makes no sense however.
and there is no MLAT for Mode A
Why not?
Actually I think it is very difficult to do any MLAT for mode A/C. With mode S you get a unique hex address for each transmission so at least you can combine all the transmissions from one source and calculate the position. For mode A/C you can only guess maybe using the squawk but if multiple planes use 7000 in the same area things get difficult.
But is mode A/C still a thing we should worry about in Europe? At least in Germany it seems to be so rare it is not worth any detection efforts.
I think that is exactly why one doesn’t see any (?) Mode A/C targets on the tracking sites. If two Mode A/C targets (with the same squawk) crossed each other, on a similar track, you would lose both of them for ever 
Sebastian_G wrote:
But is mode A/C still a thing we should worry about in Europe?
In Europe, yes. Most countries don’t mandate mode S for VFR. In Sweden, most light aircraft that are not used for IFR still have mode A/C transponders.
Flew by Goodwood this morning to see what’s what with this TIS trial. Got a good connection to their system which got me weather, but I saw no traffic.
Peter wrote:
if you only get a 40nm radius, you will need an awful lot of transmitters to cover the UK: hundreds.
I wonder what is cheaper – lots of these ground stations, or having ADS-B in/out installed in every aircraft? Even those without an electric system can use batteries, last I checked. The UAVs are using very small and low power usage transmitters.
ADS-B out for the Trig transponder is about $500 – two tanks of fuel. Seemed like the courteous thing to do. Now I need to figure out if I add FLARM out…
There is absolutely no business case to support all the ground stations, and there never will be. That aspect has to be a publicity gimmick by the hardware vendors; it seems to be a SOP nowadays.
And you don’t need them for wx; at the levels 99% of GA flies, you can get it on your phone via 4G
I think the biggest problem is that the CAA is not able to openly state the real reason for doing this, which most people think is a due diligence ar*se-covering exercise for an anticipated GA-drone collision in Class G.
ADS-B IN can draw very little power – as the various boxes already out show. But also drones are not short of power; they have relatively huge batteries, and the big ones (diesel or turboprop, etc) obviously have loads of power, so they could have a normal Mode C/S transponder so they show up on TCAS. One has to remember airliner TCAS cannot see ADS-B OUT traffic. But then airliners fly most in CAS, while presumably the intention is for droves to not fly in CAS (except the big American ones).
So I am not sure of the thinking behind this. Perhaps they want to avoid another “Mode S war” like we had 10-15 years ago, so they don’t want to mandate ADS-B IN.
Peter wrote:
Does anyone know what device can receive this data – apart from (obviously) Uavionix?Normally TIS is sent over 1090ES i.e. Mode S, so a GTX330 can receive TIS in the US, and somehow feed it to some compatible display.
UK ATC rejected TIS many years ago, citing that the cost would be ~100k per radar.
TIS is a mode S product provided by a mode S radar facility. TIS uses the mode S transponder capability to exchange messages from a mode S secondary radar site. The TIS targets are transmitted from the radar site on 1030 MHz, not 1090 MHz. The target data is crude and includes a relative altitude of the target if supplied by the target. The position is relative to the client transponder location, that is it is centric to just one aircraft, so not usable by other aircraft listening in on the frequency. I have only seen TIS implemented in the US and even then not all mode S radar sites have this capability.
TIS-B is an ADS-B product. The -B gives it away and distinguishes TIS-B from mode S TIS, which is sometimes called TIS-A to distinguish it from TIS-B. In the US it is transmitted from an ADS-B ground station on either 1090 MHZ or 978 MHz. TIS-B is the location in terms of latitude-longitude and altitude of the target so any aircraft with a receiver and listening in can determine the position of a target. The test is using TIS-B broadcast on 978 MHz and can be received by any ADS-B receiver that receives ADS-B on 978 MHz. There are tons of portable devices and certified devices on the market. In the US the devices are ubiquitous and can be built by anyone for about $150. There are numerous manufacturers, most prominent being Appareo with the Stratus, uAvionics with the Sentry, and Garmin with the GDL 5X. They price their offerings in the $500 to $1000 range. The GTX 330ES does not have an ADS-B In capability, but the GTX 345 does as does the L3 Lynx. UAT is preferred as the receiver because it has the bandwidth to include weather products as well as traffic TIS-B A ground station is fed with targets from secondary radar and those that are not ADS-B Out but include an altitude can be converted to their equivalent latitude-longitude and transmitted as a TIS-B target. Ghosting is an issue because your own ship will cause a ground station to generate a target, so means of the receiver are designed to determine which target is own ship and suppress it from display and alerting. Altitude is needed from the target to determine latitude and longitude or a secondary radar return. Other sources of position that include altitude may also be used.
In the US, TIS-B was only generated for clients that also had ADS-B Out. That means that if you don’t have ADS-B out, you can’t become a client and cause TIS-B targets to be broadcast around your position. Outside the US, without an ADS-B out mandate that covers almost all aircraft, TIS-B could simply be transmitted for mode A/C/S targets or other targets where the ground station can determine location. It is pretty much a defacto standard that any certified ADS-B receiver is dual frequency, in that it can receive targets on 1090 or 978 MHz. Any manufacturer now a days that only supports one frequency is a dinosaur..
Peter wrote:
Is there any way to merge this with ex-TAS6xx traffic data?
The Garmin systems integrate the L3, Avidyne, or Garmin TAS/TCAS, but the integration is that the ADS-B In receiver is also fed by the TAS/TCAS data and does the integration. IOW, you disconnect the TAS from the MFD/GPS and hook it up as an input to the ADS-B In receiver for the integration. The GTX 345 and the GDL 84/88 support this.
