Which part of the link are you referencing? The spiral story I would assume for this thread. Good link with many topics that are discussed here.

From the hyperlink about the spiral (from link above) a small snippet:

My buddy witnessed the first test up in the flats and told me about it. I only got to see the second one. And it looked just like what was photographed in Norway. The spiral motion of the illuminated ionosphere is controlled by the computer. That's what it looks like when they paint the atmosphere. They have to keep painting it to maintain a specific shape so the low frequency transmission will be reflected where they want it to go.

They don't use it for radar anymore. The heaters are now used for things like ground penetration tomography and blasts of electromagnetic waves.