Tom wrote:
There are links on the articles page to Hi-res photos of the dipoles and
the location of their facility.

From the article...

Mr. Battis described the unique nature of the HAARP array, consisting of
180 transmitters distributed over 35 to 40 acres of land, with a
frequency range of 2.65 to 10 megahertz.

http://www.af.mil/news/story.asp?id=123193118



There's plenty of detailed design information on HAARP available in the
public literature. A bunch of technical papers on the antenna design
and performance, the big transmitters (Eimac 10kW tetrodes) , how they
control and phase it, etc.

google "HAARP IEEE" and you'll get plenty of hits. Most of the pubs are
in the mid 90s.