Radarspotting

Y I from the north east
new boy just got airnav pro dead cheap works well but dont have antenna up high it has a arc of 190 degs out over the north sea and a bit more ne to sw ish .two things i need to know ,how out will standard antenna will pickup and can use a 70cm/2m antenna . and why does it pick aircraft but show on map ?
many thanks
danair007

Welcome Danair007, the fun now begins

Welcome.

I'm not clear on your two questions.

Ideally you should use an antenna that's tuned for 1090 MHz and install it as high as possible to get the most range.

But aircraft messages are "line of sight" and they won't normally bend around obstacles.

And not all messages contain positional data, without which they can't be plotted on a map, except those that can be plotted using something called Multilateration, MLAT.  But AirNav doesn't handle MLAT.

There are some free Guides here that may help you understand more about the topic.

And there's no need to post the same question in more than one message.  I've deleted your other ones.