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www.southgatearc.org
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Drop cellphones, use RadioIntelligence officials are beginning to suspect that the terrorists involved
in the July 11 Mumbai serial blasts left the state police and the elite
Anti Terrorist Squad (ATS) clueless about their plans by discarding mobile
phones and landlines. The reason for their suspicion is a tip-off by a private networking solution provider that he had witnessed an unusually high volume of communication signals in a scrambled mode in the UHF and VHF ranges while installing broadband networking system in Aurangabad in May this year. Such signals are difficult to monitor or eavesdrop on. “Though the system is not entirely secure, it does cut down on the ability of most eavesdroppers to listen in,” said an intelligence official. Government monitors use of VHF. Police and defence establishments use it and so do FM radio stations (88–108 Mhz). “But the local police do not have the means to monitor airwaves and ascertain if somebody else is also communicating using this frequency illegally,” said the official. “Since we only keep mobile and telephone communication under surveillance, the terrorists may have resorted to the use of radio hand sets with conversations in scrambled mode,” said the officer. WHAT IS VHF & UHF? Very High Frequency designates electromagnetic waves whose frequency is between 30 Mhz to 300 Mhz. Ultra High Frequency designates electromagnetic waves whose frequency is between 300 mhz and 3.0 Ghz VHF and UHF signals are transmitted through air waves. They can be obstructed by mountains and, hence, need repeater stations to be transmitted over longer distances. VHF is ideal for short distance terrestrial communication. Hence, they need repeater stations at frequent intervals to send signals over long distances. VHF is not much affected by atmospheric noise and interference from electrical equipment, as compared to lower frequencies. It can be blocked by land features like mountains, but not buildings and other such structures. A FAVOURITE WITH TERRORISTS US security agencies recovered reading material on ‘understanding amateur radio’ from terrorists after the September 11 attacks on the WTC twin towers in New York. Terrorist organisations like Lashkar-e-Taiba (LeT) and Jaish-e-Mohammad (JeM), based in Pakistan-occupied Kashmir and operating in Jammu and Kashmir (J&K), are known to use communication equipment of Japanese and US make. They mostly use VHF (Very High Frequency)/UHF (Ultra High Frequency) for intra-regional communication. They have set up communication stations (repeaters) in the Pir Panjal mountain range, which lie between PoK and J&K. The IB believes that Naxals in Andhra Pradesh, Chhattisgarh and Madhya Pradesh also have gained expertise in using VHF and UHF for intra-regional communication
Source: Mumbai Mirror
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