[Lonesome in Massachussets]

Some primary radar provide altitude, either by using a pencil beam (like a fire control radar) or surveillance radar with stacked beams. They transmit a big honking fat fan beam like a conventional surveillance radar and receive on a bunch of beams stacked in elevation. You can use the power ratio of the signal in adjacent beams to estimate elevation angle, and thence calculate height.

The png won’t embed, but look a figure 3 in this presentation:

http://www.radartutorial.eu/06.antennas/an12.en.html

As a practical matter, if the target is low to the horizon, even with a pencil beam, the scatter off the surface adds to the direct return in an unpredictable fashion, making elevation measurements unreliable. From about one beamwidth in elevation up, it’s pretty reliable.

[zipper]

Some primary radar provide altitude, either by using a pencil beam (like a fire control radar) or surveillance radar with stacked beams. They transmit a big honking fat fan beam like a conventional surveillance radar and receive on a bunch of beams stacked in elevation. You can use the power ratio of the signal in adjacent beams to estimate elevation angle, and thence calculate height. The png won’t embed, but look a figure 3 in this presentation: http://www.radartutorial.eu/06.antennas/an12.en.html As a practical matter, if the target is low to the horizon, even with a pencil beam, the scatter off the surface adds to the direct return in an unpredictable fashion, making elevation measurements unreliable. From about one beamwidth in elevation up, it’s pretty reliable.

Thanks for that. I think it was supposed to be Malaysian military radar that gave that 45k reading. Practically speaking, what would militaries want with a radar that couldn't show elevation? After all enemies invading your airspace don't normally squawk mode c!