Hardware Error?

[tarbat]

In any case, it seems repeatable to see more stable returns during slow hours (not a very large window of opportunity around here).

I guess you could test with the standard antenna rather than your DPD to simulate a reduced volume of messages in order to help diagnore the cause of the problem.

Also test with network OFF and no filters (such as ADS/B only) applied.

[FL350]

I have 4GB RAM in which at least 2 is free during typical operation with the software. The CPU isn't over tasked, either. Perhaps 20 per cent max.

Is that 20% of a single CPU core, or across all cores?  For example, if it's a quad core CPU, then 25% would be max'ing out a single core.

What I have noticed since my last post is that the most annoying part of the problem is occurring during heavy traffic periods. I typically return 500 - 800 (and above) messages per second during these times.

I guess you might be getting data collisions with high message volumes - ie. messages being received at the same time interfering with each other.  Maybe others in high traffic areas can comment.

I still never see 'My Flights' Time Out at all anymore, but this is much less bothersome to me.

Is that with the network on or off?  And what exactly are your timeout settings - the two values for local flights?  For example, I use 13 seconds and 107 seconds, so aircraft get marked as TIMEOUT after 13 seconds, and dissapear after another 107 seconds - so appear with TIMEOUT status for 107 seconds.

That's about 25% of a single core. 2 cores are typically 'parked', btw., and this behaviour occurs regardless of network being on or off.

[FL350]

In any case, it seems repeatable to see more stable returns during slow hours (not a very large window of opportunity around here).

I guess you could test with the standard antenna rather than your DPD to simulate a reduced volume of messages in order to help diagnore the cause of the problem.

Also test with network OFF and no filters (such as ADS/B only) applied.

I have checked it with the stock antenna before and seem to remember it didn't act up as much. It certainly wouldn't hurt  to try again (and with filters/network off as you suggest).

In fact, I'll try both, then each suggestion independently. I'm not sure that I've turned off the filter and network simultaneously.

If you happen to be watching the network now, you'll notice the ground returns disappear from JFK. Kudos to the DPD! Also, my range was hugely expanded with this setup. What a nice aerial!!!

Cheers

[tarbat]

If you happen to be watching the network now, you'll notice the ground returns disappear from JFK. Kudos to the DPD! Also, my range was hugely expanded with this setup. What a nice aerial!!!

Sorry, I don't have a network subscription anymore :(  Yes, the DPD is a great antenna, but I guess there is a chance that it's overloading your system with a large message volume.  Non-ADS/B messages are a lot shorter than ADS/B messages, so could be colliding with ADS/B messages that then get lost/corrupted.  Maybe someone with a similar message volume can comment - I rarely get above 80 messages per second!!

[FL350]

If you happen to be watching the network now, you'll notice the ground returns disappear from JFK. Kudos to the DPD! Also, my range was hugely expanded with this setup. What a nice aerial!!!

Sorry, I don't have a network subscription anymore :(  Yes, the DPD is a great antenna, but I guess there is a chance that it's overloading your system with a large message volume.  Non-ADS/B messages are a lot shorter than ADS/B messages, so could be colliding with ADS/B messages that then get lost/corrupted.  Maybe someone with a similar message volume can comment - I rarely get above 80 messages per second!!

I've just connected the stock aerial and am averaging about 250 / sec. I'll have to leave this connected for a while (of course at the expense of range and returns) and make some observations.

Judging by your locale you get more or less northernmost transoceanic flights, correct?

[tarbat]

Judging by your locale you get more or less northernmost transoceanic flights, correct?

Yes, a lot of transatlantic flights (ADS/B) and local ModeS civilian and military aircraft.  My main interest is military from the local airbases.

Good luck with the testing, and let us know how you get on.  It really doesn't sound like a hardware problem to me.  It may be that with a range of 200+ nm your receiving so many ModeS messages that the ADS/B messages get corrupted mid-transmission.

[CoastGuardJon]

Hi all, I don't thinks I've ever had solid trail lines, always broken/breaking up and bits disappearing as in :

[FL350]

Good luck with the testing, and let us know how you get on.  It really doesn't sound like a hardware problem to me.  It may be that with a range of 200+ nm your receiving so many ModeS messages that the ADS/B messages get corrupted mid-transmission.

I'll let it run on both antennas for a few days and compare. I would consider this to be a serious limitation if it were simply the inability of the radarbox to handle that kind of data. It would seem countless others in congested areas of Europe would have encountered the same issue. Either way I eagerly await to hear from others with similar message returns.

Regards

[FL350]

Hi all, I don't thinks I've ever had solid trail lines, always broken/breaking up and bits disappearing as in :

Hi CGJ,

It seems from the screenshot that you're displaying network data. Do you radarbox returns 'punctuate' in the same manner? I'll assume this is just a good example of your local returns (dotted)...

[tarbat]

Hi all, I don't thinks I've ever had solid trail lines, always broken/breaking up and bits disappearing as in :

Jon, we're discussing local hardware received aircraft, not network aircraft.  The trail lines will always be broken for network aircraft since you only receive position data every 20 or 30 seconds from the network.

I would consider this to be a serious limitation if it were simply the inability of the radarbox to handle that kind of data.

Of course I could be totally wrong about the explanation!!  Although I don't think its a limitation of the Radarbox, since if the Radarbox receives an ADS/B message that gets corrupted by a ModeS message transmitted at the same time, the checksum error checking must reject the ADS/B message.

I would imagine that as message rates increase then the chances of data collisions also increase.  At 800 msgs/sec, that's almost one message every millisecond, with an increasing chance of one message being corrupted by another.  And it's always more likely that the longer ADS/B message will get corrupted.

NASA have done some research on ADS/B message collisions, and came to this conclusion:

ADS-B performance trends were confirmed. Areas of increasing traffic density such as aircraft converging on a meter fix, showed higher probabilities for message collisions. With increasing traffic levels, overall reception probability decreased. When comparing to the industry standard LA Basin 2020 scenario for required traffic density to test ADS-B performance, the Joint Experiment had much fewer targets broadcasting ADS-B, especially nearer to LAX. Joint Experiment traffic levels do not follow the rapidly increasing trend close in to the airport because the significant impact of Mode A/C messaging over 1090Mhz from other vicinity airports and General Aviation traffic was not modeled.

[FL350]

Many thanks Tarbat,

I've perused the NASA document and found it quite interesting. Perhaps the diminished returns I'm seeing are indeed typical of high traffic convergence limitations of the technology itself. Time will ultimately tell I suppose... I'd like to compare to other users in similar conditions.

I did connect the stock aerial and seemed to confirm that radarbox (or Mode S/ADS-B) is more stable with a weaker signal during heavy traffic. I've also confirmed that my radarbox (and assume others) will not show timeout flights at all when set to filter ADS-B only flights. They do show up for non-filtered flights for the most part, but occasionally drop off even in strong reception areas. That may be related to message collisions and/or an overloaded chipset as well.

FL350

[tarbat]

I've also confirmed that my radarbox (and assume others) will not show timeout flights at all when set to filter ADS-B only flights.

Remember that ADS-B equipped aircraft also transmit non-positional ModeS messages.  So, as an aircraft leaves your coverage area, the ADS-B messages may have stopped getting through intact, but the occasional non-ADS-B message (eg Altitude, FlightID, Squawk, etc.) will still be getting through intact.  Non-ADS-B messages are more likely to get through intact because they're shorter - 56µs against 112µs for ADS-B messages.

So, the aircraft hasn't timed-out, but you've stopped receiving ADS-B messages.  That's why the aircraft simply dissapears from your MyFlights list if it's filtered for ADS-B only.  They should still appear as timed-out flights (in grey) on the map.