In January and February of 1996, using an advanced cranial communications system which utilizes a phenomena called the microwave auditory effect, microwave Hearing, or Frey Effect, agents of the US Secret Service hammered at me continuously, causing me all sorts of problems. You can see the technology and its perceivable effects described in a document I personally got declassified from the US Army Security and Intelligence Command in 2006 entitled, "Bioeffects of Selected Nonlethal Weapons," on page 6 of the main document (a copy of the letter from the army is the first 2 pages) under, "Incapacitating Effect: Microwave Hearing." A copy of this document is on the Wired Magazine website at http://www.wired.com/images_blogs/dangerroom/files/Bioeffects_of_Selected_Non-Lethal_Weapons.pdf and there is a well written Wired Magazine article, dated February 8th, 2008 entitled, "Report: Nonlethal Weapons Could Target Brain, Mimic Schizophrenia" at http://www.wired.com/2008/02/report-nonletha/
During this time, due to me remembering certain events in my past prior to that, I was able to figure out who was responsible for the unwanted communications and other events. It also has to do in large part with my being able to figure out exactly what technologies were being employed and who would use this specific combination of using these techniques and very exotic and difficult to get technologies. Presidential protection, and by extension the US Secret Service, is the most obvious and really the only choice for the combination they are using of technologies and techniques. I'll get more into a comprehensive description of each of these later.
See, the technology is such that the perceived effects (i.e. the communications, etc.) are nondirectional in nature, meaning that a persons normal ability to determine direction because of the stereo effect of having two ears does not apply in this case. It makes locating the source of the communications very difficult because you can't tell where they came from.
In addition, what could you realistically do even if you succeeded in locating them? They would just hide behind their badges and claim some legitimate purpose for their location even though there really wasn't one. And to make things even worse/more difficult, they are always fully mobile, even while communicating. So even if you managed to figure out which direction it was coming from, they could easily relocate before you could get there and then you would have to start all over trying to determine their new location.