I've followed the topic of passive radar off and on for several years. For those who don't know what it is, it's where you have a radio receiver that listens for the radar sweep and transponders from aircraft being pinged, and on its own it composes what the ATC radars are seeing right there on your PC. I've noticed this seems to have taken off in the US about as fast as a wet sponge. Either that, or all the data is behind paywalls somewhere.
I do know about Passur, but that's limited to just a handful of terminal areas, it isn't very flexible, and to usurp most of the fun, it can't be used with LiveATC because of the delay. I know the ASDI (FlightAware) feed imposes a 5-minute delay by contract stipulation, but I'm not aware of any regulation that says 5-minute delays have to be imposed on radar graphics collected directly off the radio. So you would think a couple of enthusiasts with several hundred bucks would have a cool "live radar" of NYC, O'Hare, or some other interesting place so we can get in on the action with LiveATC and see how the controllers really push tin. Nope.
Can anyone shed some light on this? Passive radar does seem to be a blossoming hobby in Europe, probably due to their lack of ASDI, and it would have the potential to be a lot of fun in the US. However it seems like only two manufacturers of the boxes have cornered the market, there's still no cheap Chinese knockoffs, and what passive radar feeds there are in the US isn't being shared for public consumption.
Or maybe I'm just not on the right websites.