[wglb]

In my previous house, there were a large number of helicopters flying. Partly due to a tour company nearby. But the ADSB picked up very few of them.

I think in certain areas they have a different frequency for an ADSB equivalent.

[dingaling]

Not a different frequency, just a different protocol. Mode-S doesn't transmit position information so location can't be easily determined unless several receivers collaborate.

[sandos]

My receiver was mainly setup for MLAT where no mode-s is usable. Its works fairly well, but at times adsbx has had very bad receivers sending faulty MLAT data corrupting all the nearby tracks. But it seems to work well for now.