Oh dear. There's some news for our 9/11 truthers, anti-vaxers and Zeitgeist groupies... and it's all bad. Not only do tinfoil hats not block government mind control radiation, they may amplify it. From a study at M.I.T. labs -
Among a fringe community of paranoids, aluminum helmets serve as the protective measure of choice against invasive radio signals. We investigate the efficacy of three aluminum helmet designs on a sample group of four individuals. Using a $250,000 network analyser, we find that although on average all helmets attenuate invasive radio frequencies in either directions (either emanating from an outside source, or emanating from the cranium of the subject), certain frequencies are in fact greatly amplified. These amplified frequencies coincide with radio bands reserved for government use according to the Federal Communication Commission (FCC). Statistical evidence suggests the use of helmets may in fact enhance the government's invasive abilities. We speculate that the government may in fact have started the helmet craze for this reason.
When it comes to mind control, the government doesn't hold a candle to christian whacknut radio.
I work for a hi-tech antenna company that builds lots of funky stuff for the government. (Sorry, no mind control antennas.) If you actually put any concave shaped metal on your head, you basically focus the radio waves to some point inside your head. This would increase the "gain" of the signal. It acts like a satellite dish reflector pointing to it's focal point, where you would find the "gain feed". Which, in this case, would be inside your head.