intervention design

These four examples of standard commercial wireless transmitters/ receivers demonstrate that output power of these category of device does not exceed 10Mw. In other words, the receiver expects any signal coming from the 2.4Ghz range, 10Mw is the minimum power needed to transmit the information between two devices.

Speculating the idea of ‘a stronger signal always override the weaker one’, a system that has at least three times the capacity of transmission and a powerful antenna should be able to suppress the signal of this systems and reach the receptor device with more efficacy.After long research on the Internet to find a transmitter capable of sending a stream way over 10Mw. A 2W powered room-to-room transmiter was found in a Chinese store in Nanjing and shipped over for preliminary tests.

Pairing the specifications of the sample transmitters with the last one, the AAVD401 operates using the same frequency range – 2.4Gz and has a much superior power of transmission. Almost 20 times more powerful than the standard ones. ered from 9V to 12V.

The mobile transmission system is powered by a sealed acid battery capable of generating 12V/12Am of power, and lasts for one hour with the equipment switched ON. However, for securing that the power of the battery does not cause overload on the transmitter and regulate the flow of power from the source to the device some adjustments need to be made. In this case, use a Voltage Regulator that brings the 12V source to 9V and feeds the device constantly on this value.

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The same test was made in a different location, this time with more layers of networks, and the result was the same. The device was so powerful that it could provoke transformations on a the whole network topology. This idea yields to possible interventions including computer networks in the target of transmission.

The system is perfectly working on a fixed site. However, for the purpose of the intervention, the system has to be upgraded to become mobile and easy to use. The effects where just noticed after other people with computersin the same location started to notice that when the system was ON the networks crashed. Unfolding this unexpected dimension of the project, more tests dedicated to the influence on the device on networks were made.

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For this purpose a circuit was designed with a power input of 12V and output of 9V. Image of the regulation system As the following scheme illustrates how the voltage flows from the battery to the transmitter.With the battery attached to the device, it becomes mobile and it is ready for the intervention. Turning on the camera to play the loop and connecting the wires from the battery in the transmitter sets the system ON and ready to broadcast.

The first trials with the TakeOver system were made with the Giga Air 3451 Camera and Monitor Kit. The system was connected according to the instructions on its manual and was left in operation while assembling the transmission system. Turning on the TakeOver system the signal was instantly override and the image on the monitor changed for the transmitted one. The system successfully suppresses the signal. While working on the tests something unexpected happened. The system not only suppressed the signal but also interfered in the wireless networks of the location.

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N12CX Wireless Cam
Frequency: 2.4GHz
Channel selection: 4
Transmission range: 100m
RF output power: 10mW

GigaAir 3451 Camera Kit
Frequency: 2.4GHz
Range: 100m
Power requirements: 9V
RF output power: 10Mw

N37CX Wireless Cam
Frequency: 2.4 GHz
Channel selection: 4
Transmission range: 100m
RF output power: 10Mw

HandHeld Baby Monitor
Frequency: 2,400~2,483
Range: 100m (300ft)
RF output power: 10Mw

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