[TowerTalk] Guerilla RF links

[Steve Sacco NN4X]

Why Ham radio, radios, and antennas rock!


http://www.economist.com/node/18386151



The Economist

Tuesday March 22nd 2011



Unorthodox links to the internet

Signalling dissent


Savvy techies are finding ways to circumvent politically motivated 
shutdowns of the internet

Mar 17th 2011 | from the print edition



WITH a tin can, some copper wire and a few dollars’ worth of nuts, bolts 
and other hardware, a do-it-yourselfer can build a makeshift directional 
antenna. A mobile phone, souped-up with such an antenna, can talk to a 
network tower that is dozens of kilometres beyond its normal range 
(about 5km, or 3 miles). As Gregory Rehm, the author of an online 
assembly guide for such things, puts it, homemade antennae are “as cool 
as the other side of the pillow on a hot night”. Of late, however, such 
antennae have proved much more than simply cool.

According to Jeff Moss, a communications adviser to America’s Department 
of Homeland Security, their existence has recently been valuable to the 
operation of several groups of revolutionaries in Egypt, Libya and 
elsewhere. To get round government shutdowns of internet and 
mobile-phone networks, resourceful dissidents have used such makeshift 
antennae to link their computers and handsets to more orthodox 
transmission equipment in neighbouring countries.

Technologies that transmit data under the noses of repressive 
authorities in this way are spreading like wildfire among pro-democracy 
groups, says Mr Moss. For example, after Egypt switched off its internet 
in January some activists brought laptops to places like Tahrir Square 
in Cairo to collect, via short-range wireless links, demonstrators’ 
video recordings and other electronic messages. These activists then 
broadcast the material to the outside world using range-extending antennae.



According to Bobby Soriano, an instructor at the Philippine branch of 
Tactical Tech, a British organisation that teaches communication 
techniques to dissidents in five countries, such antennae can even foil 
government eavesdropping and jamming efforts. Directional antennae, 
unlike the omnidirectional sort, transmit on a narrow beam. This makes 
it hard for eavesdroppers to notice a signal is there.

Citizens banned?

Another way of confounding the authorities is to build portable FM radio 
stations. One broadcasting expert, who prefers not to be named but is 
currently based in Europe, is helping to develop a dozen such “backpack” 
radio stations for anti-government protesters in his native land in the 
Arabian peninsula. Though these stations have a range of only a few 
kilometres, that is enough for the leaders of a protest to use them to 
co-ordinate their followers. The stations’ operators act as clearing 
houses for text messages, reading important ones over the air for 
everyone to hear.

Conventional radio of this sort cannot, unfortunately, transmit video or 
web pages. But a group called Access, based in New York, is trying to 
overcome that. To help democracy movements in the Middle East and North 
Africa get online, it is equipping a network of ham-radio operators with 
special modems that convert digital computer data into analogue radio 
signals that their equipment can cope with. These signals are then 
broadcast from operator to operator until they reach a network member in 
an area where the internet functions. This operator reconverts the 
signal into computer-readable data and then e-mails or posts the 
information online.

Satellites provide yet another way of getting online, though they are 
expensive to connect to. It is, however, beyond the authorities in most 
places to shut down a satellite operated by a foreign company or 
country. The best they can do is try to locate live satellite links 
using radiation-detection kit similar to that supposedly employed in 
Britain to seek out unlicensed televisions. The result is a game of cat 
and mouse between the authorities and satellite-using dissidents. 
Tactical Tech, for example, has trained dissidents in five countries to 
rig satellite dishes to computers in order to get online. It advises 
some users to log on only for short sessions, and to do so from a moving 
vehicle.

Such dishes can also be repurposed for long-range internet connections 
that do not involve satellites. Yahel Ben-David, an electrical engineer 
at the University of California, Berkeley, who has designed secret 
cross-border links to the internet for people in several countries, does 
so by adding standard USB dongles designed for home Wi-Fi networks. Thus 
equipped, two properly aligned dishes as much as 100km apart can 
transmit enough data to carry high quality video. Moreover, the beam is 
so tightly focused that equipment a mere dozen metres away from its line 
would struggle to detect it.

Creative ideas for circumventing cyber-attacks even extend to the 
redesign of apparently innocent domestic equipment. Kenneth Geers, an 
American naval-intelligence analyst at a NATO cyberwar unit in Tallinn, 
Estonia, describes a curious microwave oven. Though still able to cook 
food, its microwaves (essentially, short radiowaves) are modulated to 
encode information as though it were a normal radio transmitter. Thus, 
things turn full circle, for the original microwave oven was based on 
the magnetron from a military radar. From conflict to domesticity to 
conflict, then, in a mere six decades.