ADSB & AIS Long Distance Reception page


#1

For anyone who is interested, I’ve created a facebook page catering for people who are interested in observing ADSB (and AIS) signals beyond the usual line of sight distances, guided by tropospheric ducting.
Be great to hear from you if this is your thing.
https://www.facebook.com/groups/383549115453813/

Leigh
VK2KRR


#2

Hi Leigh,

It may sound unbelievable, but some of us do not have Facebook accounts. It’s prompting me to login, or to create an account, something that I’ll politely decline.


#3

Ditto. Nothing to do with this latest data issue either.


#4

I also have an interest in increasing the range of my ADSB and AIS receivers.

I also do not have a facebook account and no intention of signing my life away.

S.


#5

Given Facebooks recently publicised transgression (50 million this time), if I had an account, I’d delete it.


#6

Just dont put your personal information on Facebook, like me, its pretty easy to do. I dont tell them anything much at all. For example, I went to Scumbag College at Oxford :slight_smile:
You dont even have to put your real name if you dont want to. I set up an account for a friend of mine who’s also always been skeptical, but I just used part of his radio callsign for the name.

Its not unbelievable for me to hear that there are people without Facebook accounts, each to their own, I was just letting people know, who do use facebook, as there was no dedicated page for long distance observations on FB previously.

Leigh


#7

(post withdrawn by author, will be automatically deleted in 24 hours unless flagged)


#8

@Dxista
@geckoVN
@belzybob
@SweetPea11
@VK2KRR


#9

Quoting someone who commented about the web page above:

"Each “post” is a record with a field called “deleted”. You can make that field True. You can’t remove that record.

“Deleting” only gives the database owner one more piece of information about you: that you wanted to delete that record."


#10

#11

Now that we agree that Facebook is possibly not in the users best interest would it be possible to have a discussion in this forum on the original topic.

To start, i live in Melbourne and occasionally get a packet with location from QF64 which flies over head coming from Johannesburg to Sydney.

The furthest away that i have seen is about 1000km when it is well south over the great Australian Bight.

It is where it is scheduled to be and about 30 minutes later i get consistent reception from it.

No idea what propagation gets me that one packet.

S


#12

First question is are you seeing it or is a shared report e.g. through Planeplotter or similar? I get some shared reports over the Indian Ocean that way. If it was direct, then there are some mechanisms that could come into play, but I’m unsure of the probability at frequencies as high as 1090.

  1. Atmospheric ducting. Usually occurs where warm moist air is overlaid with a cooler drier layer of air. The inversion zone between the two layers acts like a radio mirror, ‘ducting’ the signal and prevents the signal shooting off into space. I believe that I have seen one instance recently where I picked up a small number of returns below 10,000’ at a range of just over 250nm. I know that those conditions can occur over the Bight as amateurs have exchanged signals between SA and WA, but at lower VHF frequencies.

  2. Meteor scatter. Signals are reflected when they hit the gas cloud behind a meteorite entering the earth’s atmosphere. Again I know and have used it at lower frequencies, but I’m unsure of the effects at 1090.

  3. Ionospheric reflection including ‘Sporadic E’. Extremely unlikely at frequencies like 1090.


#13

I am looking at the data in piaware locally and also feeding it into adsbScope locally with no other inputs or sharing. adsbScope gives me a 10 hour history indicator.

as well as

  1. Tropo scatter

  2. Meteor Scatter

  3. Airplane scatter.

No doubt there are more modes of enhancement that others will suggest.

I’m just suggesting that there is fairly good evidence that I am receiving a valid packet with identification and location from an aircraft which is about where it should be.

I’ll try and capture a screen shot next time.

S.


#14

Tropo scatter is also a possibility, although tropo scatter links generally involve high power and high gain directional arrays due to the minute amount of power that gets to the receiver. Meteor scatter I’ve already mentioned. Aircraft scatter is again possible, but I’d suggest marginal at the range you’ve mentioned.

There is also the possibility of modes mixing over the same path, for example at VHF ducting combined with sporadic E is not uncommon. Again, any ionospheric involvement is very unlikely at 1090.


#15

I think it is all unlikely but so is winning the lottery. Sometimes, to someone it just happens and with such little evidence it is only possible to speculate rather than prove.

Have a look at this site. http://62.251.100.171:1090/ Often he has a plane out to the east at between 700 and 1000km.

If you look at the plane on Planefinder or Flightaware or Flightradar24 you see the altitude or speed or track just doesn’t make sense or the plane appears to be over a different continent.

At least my one or two packets pass a mild sanity check.

S


#16

I’d take some of the traffic on that link with a pinch of salt.


#17

I agree but I think it is also polluting some of the services it is feeding,

S


#18

Looking at his feeder I doubt it. Radarcape in a low noise environment should do very well. It has built in CRC checks to minimise garbage.


#19

SweetPea11 if your in Melbourne I would be keeping an eye on your reception tonight and the morning as tropospheric ducting potential is high.


#20

My location is just at the foot hill of himalaya…so the only airport of Bhutan ,Paro is within my range…but due to high hills,unless they achieve an optimum altitude they aren’t seen on skyview. But sometimes amazingly one or two positions are reported from more than 400 km away from Tibet and mainland China.