MIT Study on Tin-Foil Hats :-)

Bill Stewart bill.stewart at
Thu Nov 10 11:43:21 PST 2005

The page was actually published in February, but showed up at 
(Hmm.  Looks like Slashdot just got it also, so it'll probably
be a bit slow downloading.  I've included the text here,
but the pictures make it worthwhile.)

On the Effectiveness of Aluminium Foil Helmets:

An Empirical Study

Ali Rahimi1, Ben Recht 2, Jason Taylor 2, Noah Vawter 2
17 Feb 2005

1: Electrical Engineering and Computer Science department, MIT.
2: Media Laboratory, MIT.


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 theorize that the government may in 
fact have started the helmet craze for this reason.

It has long been suspected that the government has been using satellites to 
read and control the minds of certain citizens. The use of aluminum helmets 
has been a common guerrilla tactic against the government's invasive 
tactics [1]. Surprisingly, these helmets can in fact help the government 
spy on citizens by amplifying certain key frequency ranges reserved for 
government use. In addition, none of the three helmets we analyzed provided 
significant attenuation to most frequency bands.

We describe our experimental setup, report our results, and conclude with a 
few design guidelines for constructing more effective helmets.

Experimental Setup

The three helmet types tested
The ClassicalThe Fez
The Centurion

We evaluated the performance of three different helmet designs, commonly 
referred to as the Classical, the Fez, and the Centurion. These designs are 
portrayed in Figure 1. The helmets were made of Reynolds aluminium foil. As 
per best practices, all three designs were constructed with the double 
layering technique described elsewhere [2].

A radio-frequency test signal sweeping the ranges from 10 Khz to 3 Ghz was 
generated using an omnidirectional antenna attached to the Agilent 8714ET's 
signal generator.

The experimental apparatus, including a data recording laptop, a $250,000 
network analyser, and antennae.

A network analyser (Agilent 8714ET) and a directional antenna measured and 
plotted the signals. See Figure 2.

Because of the cost of the equipment (about $250,000), and the limited time 
for which we had access to these devices, the subjects and experimenters 
performed a few dry runs before the actual experiment (see Figure 3).

Test subjects during a dry run.

The receiver antenna was placed at various places on the cranium of 4 
different subjects: the frontal, occipital and parietal lobes. Once with 
the helmet off and once with the helmet on. The network analyzer plotted 
the attenuation betwen the signals in these two settings at different 
frequencies, from 10Khz to 3 Ghz. Figure 4 shows a typical plot of the 
attenuation at different frequencies.

A typical attenuation trace form the network analyser


For all helmets, we noticed a 30 db amplification at 2.6 Ghz and a 20 db 
amplification at 1.2 Ghz, regardless of the position of the antenna on the 
cranium. In addition, all helmets exhibited a marked 20 db attenuation at 
around 1.5 Ghz, with no significant attenuation beyond 10 db anywhere else.

The helmets amplify frequency bands that coincide with those allocated to 
the US government between 1.2 Ghz and 1.4 Ghz. According to the FCC, These 
bands are supposedly reserved for ''radio location'' (ie, GPS), and other 
communications with satellites (see, for example, [3]). The 2.6 Ghz band 
coincides with mobile phone technology. Though not affiliated by 
government, these bands are at the hands of multinational corporations.

It requires no stretch of the imagination to conclude that the current 
helmet craze is likely to have been propagated by the Government, possibly 
with the involvement of the FCC. We hope this report will encourage the 
paranoid community to develop improved helmet designs to avoid falling prey 
to these shortcomings.


The authors would like to thank Andy (Xu) Sun of the MIT Media Lab for 
helping with the equipment, Professor George Sergiadis for lending us the 
antennae, and Professor Neil Gershenfeld for allowing us the use of his lab 

More information about the cypherpunks-legacy mailing list