Sure, and the same would apply to the radiating half of the system. Yet most Flarm radiators are also using portable units – the typical use is glider-on-glider proximity warnings and you need those to work only in very close proximity. There is not likely to be much interest in radiating strong signals, and even less interest in radiating signals which could be picked up with amateur land stations and fed into a website database
In fact the FLARM ground stations of the OGN network routinely pick up gliders at 50-70 km range although there are so many of them that this range is rarely required. The longest range I recall seeing (I don’t sit staring at this, honestly!) was about 150km from a PC12 over the North Sea to Cambridge. Presumably he had a proper external antenna fitted. The reason for the very much greater range than in the air-air case is due partly to the use of decent antennas at the ground station (10db+ gain) and partly the use of decent (but cheap) SDR receivers based on USB TV dongles). The FLARM airborne tranceiver modules (off-the-shelf items) are pretty deaf (like most avionics).
The online database issue seems to be less of an issue than with ADSB. FLARM/OGN have IMHO done quite a good job of tackling the privacy issue by providing a user-controlled flag in the air protocol and options in the OGN database which allow user to limit access without affecting the collision alerting functionality, so the ON/OFF switch is not your only option. It isn’t perfect and relies on everybody playing nicely but so far seems to work well. Of course if somebody wants to set up a private receiver in their bedroom you can’t do anything about it (same as listening to airband voice), but that’s quite different in my view to having an anonymously accessed , searchable, historical log of everything as per FR24 etc.
Alan
Timothy wrote:
…but if I were doing it now, I would get a Garmin GTX345 transponder as well, and get ADS-B in traffic as well.
This will only display ADS-B traffic on a WAAS GNS530 and would be a limited view of traffic.
I fly with a PowerFlarm Portable box (when I remember and am not too lazy / in a hurry to put it) on the glare shield. I do get plenty of ADS-B and Mode A/C indications. Mode A/C does not have azimuth, but <shrug>
I don’t remember ever getting a Flarm target :)
NCYankee wrote:
would be a limited view of traffic.
Why? You get an integration of TAS and ADS-B.
Timothy wrote:
Why? You get an integration of TAS and ADS-B.
Assuming you have a TAS box and a compatible display, but a GNS530 is not a compatible display for the GTX345. A GTX345 in combination with just a GNS530 will display no traffic from ADS-B. If you have a GNS530 and a TAS, it will only display the TAS information on the existing GNS530. Upgrade the GNS530 to W and it will display merged traffic, but the TAS box will handle the near in collision threat traffic based on active interrogation of mode A and C targets. Some of those near in targets may be enhanced with ADS-B position if the target happens to be ADS-B Out equipped, but I would not expect it to make much difference with or without ADS-B. Of course, you will also receive ADS-B only traffic that is outside the range of your TAS, but that is not much of a collision threat but would add to situational awareness of just the ADS-B Only traffic.
In the US, the ground station fills in with TISB targets for Mode A/C and within 15 NM and +/- 3500 feet, so for most TAS units it expands the usable range to some degree depending on the existing TAS ranges. Of course with a TAS system, you don’t need to be within line of sight of a ground station and don’t have any dependency on ground radar to track a TISB target, nor do you have to worry about the latency of the radar system. Also in the US, the TISB will fill in for ADS-B Out clients that are barred from being displayed or merged because of SIL/SDA/NIC/NACp type issues, making these targets visible as well.
A system not mandated for most GA type aircraft and providing no ground based services to fill in the gaps (eg TISB) will leave a lot to be desired from a traffic system point of view, and a TAS or TCAS type system will be the best bet for the application of Enhanced Visual Acquisition.
Assuming you have a TAS box and a compatible display, but a GNS530 is not a compatible display for the GTX345. A GTX345 in combination with just a GNS530 will display no traffic from ADS-B. If you have a GNS530 and a TAS, it will only display the TAS information on the existing GNS530. Upgrade the GNS530 to W and it will display merged traffic
That is a really subtle point and has a bearing on this also i.e. the same issue will happen apparently (nobody I spoke to has been exactly clear on it) with the Sandel SN3500 EHSI and possibly every other “old” display device. It amazes me that an “older box” which can display ex-TAS605 traffic cannot display traffic which is pure ADS-B only. Why could they not make the merged traffic look like TAS traffic?? And what the KMD550 will display is anybody’s guess 
But as someone pointed out in the other thread, this should not matter in Europe because here there is no legal/certified way to radiate ADS-B without also radiating Mode S and the TAS box will pick that up.
Of course if the GNS530 also failed to display merged (ADS-B and Mode A/C/S) targets that would make it useless for the future because as people implement ADS-B OUT they would gradually disappear from view Is that really going to happen? i.e. targets which are picked up via both TAS and ADS-B will be suppressed on older devices?
Peter wrote:
Of course if the GNS530 also failed to display merged (ADS-B and Mode A/C/S) targets that would make it useless for the future because as people implement ADS-B OUT they would gradually disappear from view
Peter,
I don’t follow your statement. A 1090ES transponder is both a mode A/C/S transponder and an ADS-B Out device. They just share a common transmitter. Mode A/C transponders don’t radiate per say, they only respond when interrogated on 1030 MHz with a reply on 1090 MHz using a pulse pattern. A mode S transponder responds to Mode A and C interrogations with the same pulse pattern as an A/C transponder. The Mode S transponder also responds to mode S interrogations on 1030 MHz with a mode S reply message on 1090MHz. A mode S transponder can be uniquely addressed by its ID on 1030 MHz. Squitters are unsolicited broadcasts and are not dependent on an interrogation. They are primarily used by a mode S transponder to let other aircraft TCAS or mode S radars acquire the address. ADS-B uses squitters that are broadcast approximately once per second and have a DL code of X18’ in the message indicating that its contents are ADS-B data. Transponder replies use a different DF value. Both transponder responses and squitters occur in a mode S transponder and an ES transponder squits the ADS-B. So for a TAS unit, a target equipped with a transponder that supports ADS-B Out works like any other transponder.
I think NCYankee this is more clear to me if the USA has the same ADS-B options as Europe has i.e. no way to radiate ADS-B OUT without also radiating Mode S.
By “radiate” I mean generate packets which are visible on say a TAS605 or a GTX345. I realise some of these radiations are continuous while others need a secondary radar (or TAS) ping.
Obviously a GNS530 will display the data from a TAS605 (or similar – see post #2) box. But if a GNS530 does not display a merged target (from a TAS605-A+ADS-B, GTX355, etc) that is quite a downside for the future when there will likely be more people radiating ADS-B OUT.
