Ae Watan Mere Watan sees the British using a technique called triangulation to locate the broadcast location of Congress Radio.
The events of the film unfold in 1942, during British rule, when all private radio stations are banned due to the ongoing Second World War.
The British control the press and use it to spread their propaganda. Additionally, the leaders of the freedom movement are imprisoned before the launch of the Quit India Movement.
To counter British propaganda and spread prohibited information, Usha and her friends start their own radio station, Congress Radio.
Congress Radio proves to be a nuisance for the British authorities, who fear that they will have to release the leaders if the masses are incited.
John Lyre, an efficient police officer, is tasked with shutting down the radio and identifying its operators. Lyre employs a radio detector van to locate the radio.
However, since the van clearly stands out on the streets, Usha and her associates are able to evade the police.
All they have to do is keep watch and switch off the radio as soon as the van approaches, preventing it from detecting their exact location.
Lyre then adopts a new strategy to catch them: a technique called triangulation, which proves too difficult to evade.
A difficult-to-evade technique
Triangulation is a radio-tracking technique that enables the British to pinpoint the radio’s location with accuracy within five minutes.
It involves using two radio detector vans that simultaneously move through the streets of Bombay.
When these vans come within half a kilometer of the radio, they pick up its signal and determine the direction from which it originates.
A line is drawn from each van in the direction of the signal, and the point where these lines intersect indicates the radio’s location. This is called triangulation.
The only way to counter triangulation is by using two transmitters. Usha and Fahad decide to make use of two transmitters and position them at a distance of ten to fifteen miles from each other.
They intend to use the first transmitter, switch it off when the vans come close to it, and then switch to the second transmitter.
The vans move at a slow pace, so by the time they locate the second transmitter, the broadcast will have ended.
However, they are unable to execute their plan, as Lyre arrests their engineer and seizes their newly built transmitter.
Ultimately, Lyre and his team locate Usha using triangulation, leading to the shutdown of Congress Radio and Usha’s arrest.
Also Read: Usha Mehta from Ae Watan Mere Watan: Is she based on a real-life figure?