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The book Transmitter Hunting--Radio Direction Finding Simplified by Moell and Curlee is an excellent book on the subject. The technical aspects are universal, but the description of hunt mechanics (T-hunts) is from the Southwest California perspective. The McGraw-Hill ISBN number is 007-1560068. It is a large paperback that lists for $21.95. Also check Joe Moell's fine pages which include updates to the book as well as other hunting info.
Byon, KD6BCH has a nice equipment page. BMG Engineering has commercial pages for their DFer (used effectively by Charlie KB9DIM in the Chicago area). The most impressive value and construction of any doppler system that I had seen once appeared to be the Agrelo [now defunct] DFjr RDF. However, in action it seems to lack sensitivity compared with the Doppler Systems or Dick Smith units. The insensitivity is amazing. The outside antenna switching unit is rated down to -20C/-4F. There is some indication that it has even more problems at temperatures warmer than that. It can also be easily damaged by nearby RF. Sometimes this damage can be detected by comparing the voltage at each antenna to the antenna frame. An oscilloscope is best for this, but a voltmeter will often do the job. They are out of business and the units appear to be orphans. There will be some in the used market and somebody will probably offer service at some point.
Go to the Chicago Area Foxhunt Schedule page.