Something I have been interested in for a long time. The more we use RF for data and voice, this technique becomes more effective.

Here are a few links that may be of interest to others.

http://www.google.com/patents/US3218642

https://books.google.com.au

https://www.wpi.edu/Pubs/E-project/Available/E-project-101012-211424/unrestricted/DirectionFindingPaper.pdf

https://books.google.com.au/

http://researchonline.jcu.edu.au/21074/1/Very_small,_light_dipole_harmonic.pdf

http://www.ijstr.org/final-print/aug2014/Simulation-Of-Direction-Finding-Algorithm-And-Estimation-Of-Losses-In-An-Rwr-System.pdf

http://downloadfile.anritsu.com/RefFiles/en-US/Products-Solutions/RF-Interference-Hunting-Techniques.pdf

https://books.google.com.au/books?id=kei6zO5iBsMC&lpg=PA8&ots=VI-M59KQJb&dq=Passive%20Radio%20Transmission%20Direction%20Finder%20noise&pg=PA8#v=onepage&q=Passive%20Radio%20Transmission%20Direction%20Finder%20noise&f=false

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.20.9185&rep=rep1&type=pdf

http://www.jhuapl.edu/techdigest/TD/td3103/31_03-Grabbe.pdf