ADSB/SDR question

Mountain343

Member
Joined
Jul 21, 2009
Messages
62
Hey Everyone, not sure if I should post this here or in an SDR forum but figured I'd give this a shot first.

I sometimes stay near Luke Air Base, and in the Los Angeles region and notice that I almost never pick up military aircraft on my ADSB/SDR combo.

For example, right now I can hear and see the military aircraft out my window, and I can see a good 10 planes on the RTL1090 scope at a pretty far distance, just not the military ones.

Do they not use the same system? Do they do something different? Is there a way I can visualize them using an SDR when they're flying overhead?

Do I need a better antenna ? Like I said, I can see some planes out a pretty good distance, it says >40 >80 usually using RTL1090 ... is there another setting I should be using on the program?

Thanks!
 

vagrant

ker-muhj-uhn
Joined
Nov 19, 2005
Messages
1,644
Location
California
Some military aircraft will turn on their ADS-B equipment, but most of the time not. The website adsbexchange.com will allow you to specifically monitor military aircraft. They achieve this by multiple locations (people) sharing their feed to the site and triangulate "some" military aircraft via other signals being sent by the aircraft, as well as ADS-B if the aircraft turn it on. I'm simplifying this quite a bit, but that's basically how you "might" be able to see military aircraft in those areas. Use adsbexchange.com and when the window pops up, select the large "U" at the top to filter for military only. There is often military fixed wing and rotor aircraft in the Los Angeles area.

You can assist adsbexchange.com as well with your feed. Follow their instructions and it will help yourself and others. Still, if there aren't enough people sharing in your area triangulation will not happen. Thus, you may need to wait until others near you share. Have fun.

Equipment:
I use a DPD Productions ADS-B antenna. There are other antennas for less. Getting the antenna up above your roofline well help considerably on the range/distance. If your antenna is inside your home and you are getting 40 to 80 miles, that is fantastic. My antenna is on a 30' mast (9 meters) and I easily get 200 miles.
 

alcahuete

Member
Premium Subscriber
Joined
Jul 24, 2015
Messages
1,160
Location
Antelope Acres, California
Military aircraft (and several others) are exempt from the ADS-B requirement. Specifically:

Otherwise authorized by the FAA when the aircraft is performing a sensitive government mission for national defense, homeland security, intelligence or law enforcement purposes and transmitting would compromise the operations security of the mission or pose a safety risk to the aircraft, crew, or people and property in the air or on the ground;
 

Mountain343

Member
Joined
Jul 21, 2009
Messages
62
Some military aircraft will turn on their ADS-B equipment, but most of the time not. The website adsbexchange.com will allow you to specifically monitor military aircraft. They achieve this by multiple locations (people) sharing their feed to the site and triangulate "some" military aircraft via other signals being sent by the aircraft, as well as ADS-B if the aircraft turn it on. I'm simplifying this quite a bit, but that's basically how you "might" be able to see military aircraft in those areas. Use adsbexchange.com and when the window pops up, select the large "U" at the top to filter for military only. There is often military fixed wing and rotor aircraft in the Los Angeles area.

You can assist adsbexchange.com as well with your feed. Follow their instructions and it will help yourself and others. Still, if there aren't enough people sharing in your area triangulation will not happen. Thus, you may need to wait until others near you share. Have fun.

Equipment:
I use a DPD Productions ADS-B antenna. There are other antennas for less. Getting the antenna up above your roofline well help considerably on the range/distance. If your antenna is inside your home and you are getting 40 to 80 miles, that is fantastic. My antenna is on a 30' mast (9 meters) and I easily get 200 miles.
Thanks for the reply!

I can see them often (albeit briefly) on that website, which is why I thought I'd give it a try! They show up as ~A**** flying out of Luke, go right over my place and then disappear. But I see nothing on my RTL1090, which is what is so confusing to me, because I can see the airliners, and private planes, and helos all over the general area, but not the MilAir overhead that is being seen on the website?

If I click the aircraft it shows up as TIS-B though. I read some more that maybe I needed a 978mhz program, so I grabbed RTL-Duo and set the 2nd SDR dongle, to 978, and then both to 978 and neither seems to help.

And yeah, inside the house with just an old extended antenna I get 80 easily from my location, which is really nice. Took some monkeying around to get the best location, but just sitting on a desk here in the back room, it's consistently hitting 80 on the scope which is fun.

I just wish I could see the TIS-B whatever that is, I know others can... because it IS on Adsbexchange briefly!
 

vagrant

ker-muhj-uhn
Joined
Nov 19, 2005
Messages
1,644
Location
California
But I see nothing on my RTL1090, which is what is so confusing to me, because I can see the airliners, and private planes, and helos all over the general area, but not the MilAir overhead that is being seen on the website?
That would be normal. Same for me if I used my equipment where you are.

If I click the aircraft it shows up as TIS-B though.
Yes, TIS-B or MLAT would be the modes that you would not observe using a single receiver via ADS-B mode. Sometimes if you click on one it may say ADS-B, but not too often. Well, I should explain further. Some aircraft may show up on a list on your program, but it may not show a location. adsbexchange uses at least three feeders (people like you and me) to triangulate. In order to do that each of those computers must use accurate clock timing as well as provide their precise location. If any of that information is not exact, the positioning will not be exact of the aircraft.

I read some more that maybe I needed a 978mhz program, so I grabbed RTL-Duo and set the 2nd SDR dongle, to 978, and then both to 978 and neither seems to help.
That is for lower flying civilian aircraft in the U.S.A. not using ADS-B. I don't use that myself.

And yeah, inside the house with just an old extended antenna I get 80 easily from my location, which is really nice. Took some monkeying around to get the best location, but just sitting on a desk here in the back room, it's consistently hitting 80 on the scope which is fun.
Fantastic! By extended I think you mean telescoping. Anyways, it does not appear that you need an improved antenna.

I just wish I could see the TIS-B whatever that is, I know others can... because it IS on Adsbexchange briefly!
adsbexchange.com needs at least three feeders in order to triangulate the position of non ADS-B aircraft. Your additional feed to them may provided extended coverage allowing you to observe the military aircraft past where it disappears, unless of course it is beyond your 80 mile coverage.
 

vagrant

ker-muhj-uhn
Joined
Nov 19, 2005
Messages
1,644
Location
California
I just wish I could see the TIS-B whatever that is, I know others can... because it IS on Adsbexchange briefly!

Hmm...I am wondering if I answered this last bit fully, so here we go. In a way, yes you and others do see the aircraft signal, but the aircraft is not sending it's position so you or me individually would not see it plotted on a map.

On adsbexchange you are seeing the result of multiple people sharing their feeds and adsbexchange taking that data, triangulating it and then pushing that data out which provides the position report of the aircraft. Again, I am simplifying this, but that is what is happening and why we cannot see it on our own feeds, but observe it on shared sites.
 

GlobalNorth

Member
Premium Subscriber
Joined
May 2, 2020
Messages
265
I am within the LAFB AO and you are likely to never see military aircraft [F-16, F-35, etc.] show up on the ADS-B website. The last occurrence that I recall was when the President recently visited MCAS Yuma and one of the support aircraft landed and later departed LAFB.

Since LAFB is a fighter training base, they do not activate ADS-B for their usual ops.
 

Mountain343

Member
Joined
Jul 21, 2009
Messages
62
I just wish I could see the TIS-B whatever that is, I know others can... because it IS on Adsbexchange briefly!

Hmm...I am wondering if I answered this last bit fully, so here we go. In a way, yes you and others do see the aircraft signal, but the aircraft is not sending it's position so you or me individually would not see it plotted on a map.

On adsbexchange you are seeing the result of multiple people sharing their feeds and adsbexchange taking that data, triangulating it and then pushing that data out which provides the position report of the aircraft. Again, I am simplifying this, but that is what is happening and why we cannot see it on our own feeds, but observe it on shared sites.
Do you see it on the list tab or II/SI tab? or if I use dump1090 would I be able to see "something?" I'm not really curious about tracking/where so much as just getting an early warning as to when the house I'm at is gonna go BOOM and so I can go outside and go look :) It can be over 100 degrees out here and sitting outside waiting with binocs get's to be a bit much some days lol. But ... if the computer alerts me that they're coming my way ... I tried listening to the tower and RAPCON but I can't make heads or tails out of what i'm hearing just yet. It makes no sense to me or to what I see in the sky. Still trying to work that one out.

This is what I see on my screen though. rtl1090-scope.jpg

I am within the LAFB AO and you are likely to never see military aircraft [F-16, F-35, etc.] show up on the ADS-B website. The last occurrence that I recall was when the President recently visited MCAS Yuma and one of the support aircraft landed and later departed LAFB.

Since LAFB is a fighter training base, they do not activate ADS-B for their usual ops.
Oh! I see them all the time actually! you just have to be quick about it because they pop up and then are gone fast, but here's a screen shot from just a second ago:

1.jpg2.jpg

They show up as that _~#####* format and you can see them zip and zoom... albeit briefly and it catches about 1 out of every 6 I see/hear.

Here's a screen shot showing one on the website but nothing on my scope even though it's basically right over me
 

Mountain343

Member
Joined
Jul 21, 2009
Messages
62
So those _stuff are fighters?
Yep, confirmed standing outside watching them on the laptop and looking up above me. Every time I see the _~ and this kinda data, and look above my head, it's usually a pair of fighters frome Luke.
3.jpg

That's why I was hoping to figure out the adsb thing, so I could get better at figuring out what I was hearing on the tower and rapcon frequencies.
 

freqhopping

Member
Joined
Jan 5, 2004
Messages
5,653
Location
Lo Co VA/ FM19
TIS-B flights shown on ADSBX are the result of a radar ground station determining the location of an aircraft (often not equipped or using mode-S/ADSB) and then broadcasting that location to be received by aircraft equipped with mode-S receivers so that they all know the position of these non-broadcasting aircraft.

To receive these TIS broadcasts with your own receiver you would need to be near the source.

The TIS-B IDs displayed on ADSBX are not fixed to an aircraft.

In my area most of the TIS-B broadcasts are for military helicopters. I once saw a DC ANG F-16 working in the range at Quantico. I've also seen an F-15 during a combat air patrol.
 

Mountain343

Member
Joined
Jul 21, 2009
Messages
62
TIS-B flights shown on ADSBX are the result of a radar ground station determining the location of an aircraft (often not equipped or using mode-S/ADSB) and then broadcasting that location to be received by aircraft equipped with mode-S receivers so that they all know the position of these non-broadcasting aircraft.

To receive these TIS broadcasts with your own receiver you would need to be near the source.

The TIS-B IDs displayed on ADSBX are not fixed to an aircraft.

In my area most of the TIS-B broadcasts are for military helicopters. I once saw a DC ANG F-16 working in the range at Quantico. I've also seen an F-15 during a combat air patrol.

Ah! So I need to be closer to the radar site not the planes! That makes sense then because I'm not seeing anything on my sdr at ALL. I'll google and see if I can find more info to try and figure out the rapcon/tower convos I'm hearing because they're not making much sense to me yet.

Luke is very active today though!

1599785922616.png
 
Top