Hacker News Reader

Comment by bcaa7f3a8bbc | Hacker News Reader

A simple experiment result published by the MIT Media Lab, found tinfoil hats are not really effective. https://web.archive.org/web/20100708230258/http://people.csa...

> 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.

Full electromagnetic shielding of the entire building perhaps? Like those at the NSA headquarter. It should give you a heavy attenuation on the microwave frequency.

BTW, why don't the intelligence agencies install a software-defined radio in suspected US embassies to log the entire microwave spectrum? It will definitely yield something.

View on HN

That MIT article is bunk. Everyone knows you need a diffraction grating, to diffuse fortuitous signals.

They didn’t even try produce effective results.

Back in (one of?) the very first paper(s?) on this stuff, Frey actually pointed out that a 2x2 piece of flyscreen (of some density, I forgot which) on the temporal lobes blocks the EM/RF hearing effect. But, as I pointed out in another comment, two distinct effects exist:

One that induces EM/RF hearing, and one that induces tissue damage.

You don't even need SDR... a really simple LED and a few variable antennas would do a good job into the GHz.

For detection, yes, it can be done by an extremely simple circuit. But you would need the raw I/Q sample data over a broad frequency range to perform a technical analysis to identify the nature of the microwave. Here's when a SDR comes handy.

The LED just reveals power (detection of radiation over many visible orders of magnitude) ... it doesn't need to detect coherent I/Q, because I don't think neural effects are sensitive to phase either. Selectively cooking a brain would require relatively high power and beam forming, but not high data rate. Audio frequencies are visible (use multiple band pass filters if you like) .

You'd also want a controlled test source so you'd know if the attacker had burned it out.

Do you need a Schottky or will the plain LED work?

With the Schottky you will get better low power detection (lower forward voltage 0.18V vs 1.8V), but it doesn't inherently indicate activation (you'd want an electret or piezo speaker at least) with the same dynamic range as your eye is capable of with an LED. Of course if you have an RMS power meter with uW resolution it will be OK... but LEDs are really good.

Reply on news.ycombinator.com