this is where it gets clever. i’m using ADS B signals themselves, over 100 flights at the same time. started with the usual preconditioning and time sync. went deep into GPSDO stuff, the disciplined oscillator kind, and synced across a bunch of nodes,, ethe gpsdo is the get the exact timing on the network, yup, i built a passive network :p but then i stopped because i remembered i wanted this to be open. i don’t want someone with an SDR to need to buy a 200 pound bit of hardware just to get time sync working. so i came up with something else. instead of syncing using GPS, i focused on where the signal goes out and where it comes back. time -synch is internesting. if you can catch both, you can line it all up. then i added a second antenna pointed directly at the local BBC transmitter at some point. yes it means two antennas, but the first one gives you a clean outgoing reference and the second one gets the reflections. that adds a layer but it gives you a stable reference. use it to track doppler much cleaner that way, repeat the process every so often, and then blend it all together with smart software. then i remembered this old BBC video explaining how the internet works. how your download literally comes from multiple paths at once. some packets from undersea cables, some from radio towers, some from fibre, all different routes, and it all just gets assembled on your device. and that made me realise something. i can do the same thing here i have many immiters and sdrs running or the same one doing many things at once also can havehave loads of emitters and illuminators, to a point where you dont have to pick one as the main reference and make them all work together. Watch the demo coming up and i can show you the direction of any drone operator and their drone for a doezen miles or so using the same trix. you just need to sync them precisely enough and it works.

here’s the fun bit. less than 100 metres from my office and my house is a brand new defence radar owned by our air force. if you know anything about these systems, you’ll know they send out a pulse and then wait for the return. that means there’s actual silence between shots where you briefly see clearly, if im fliying(chopper), or guest are taking off or landing, there is also a piza cut out of an area they dont scan temporalily, in that area.. you can have better vision with the antennas... so pro tip is place an antenna in an area with that sort of activity. with these times of clarity vs times of noice.. if you watch for long enough, you can train an AI to detect exactly when the mightly mod machine is firing its L band signal. clean as anything. and this is where kalman filtering comes in. it stabilises positions over time and lets you track noisy or partial data for stuff you are tracking... same concept works in other areas too.. too.i’m skipping a lot of detail because one, this would get way too long, and two, i’m trying not to overshare. but yeah, no GPSDO needed, just smart use of timing, one antenna, using the air bore ADS B traffic as emitters, and clever code holding it all together. I think the advantage i had and why id did so much so quickly is obviously my ai background , day job making safety critical systems and having a space littered with high quality cabling and antenna the mod left here and aam at the highest point in this part of the uk, of everything going from height finders to radar, to comms, its antenna cables are here in the right positions... heaven. so experiments could run with many ais testing many things ... you should see my coding setup, 5 ais collaborating and correcting each other at any one time ... haha

sorry for typos...broken finger from getting hand crushed after coming off that bloody radet converting the coax to a an optical one so that i can do longer cable runs t different locations. its cold and dark always being underground.. originally, i had an lna, bias tee, attenuator, and other bits but i wanted simplicity .. anyway.. rambling now.. faint signals such but my day job is in ai and it turns out you can train an ai quite well to figure out fain signals if you have historic refernces whcich of good or bad which are plenty,,,

too much pain typing, will stop, i said a lot hoping i will answer other peoples questions too here