Flight safety is put at risk by broadcasting waves that have disturb the communication system of planes flying over Buon Ma Thuot and Pleiku cities since mid-April, the Department of Radio Frequency has warned.

This cartoon shows a plane being disturbed by wireless broadcasting waves while in the sky (Photo: Tuoi Tre)

Nguyen Van Thu, deputy head of the department, said the agency has directed its units to track down the culprits of the disturbance in a space area of 220 km over the two cities in the Central Highlands.

He added that not only these cities, but other localities, including those in Northern Vietnam, also suffered from the disturbance of broadcasting waves that caused interference to the communication between flying aircraft and the air traffic control station on the ground.

In a report to the Radio Frequency Directorate in late April, attached with the list of 9 flights affected by the type of wave, the Southern Flight Management Corporation, said, “We affirm that the interference by broadcasting waves is true and is ready for a coordination to detect the source of disturbance and deal remove it effectively.”

In January 2012, the Vietnam Flight Management Corporation also complained to the Directorate about the same, with a list of 29 disturbed flights reported.

Pilots heard broadcasting contents in Vietnamese while they were in the air, the report said.
“This is a serious incident that has long occurred in a wide area in the Central Highlands,” the Corp said, adding that “the interference might be caused by broadcast systems in Vietnamese.”

The Corp asked the Directorate to take measures to remove the sources of interference to ensure flight safety.

Wireless broadcast as culprit 

The interference likely comes from wireless broadcasting system on FM frequencies, Thu said.

This technique remains being used in Vietnam while it is hard to be applied in other many areas in the world, he said.

A technician at the broadcasting station in Cu M'Gar District in the Central Highlands province of Dak Lak is operating its wireless system (Photo: Tuoi Tre) 

Previously, the Directorate licensed wireless broadcasting stations to use the frequency band ranging from 87 to 108 Mhz, but recently, the band has been narrowed, 54-68 Mhz.

The adjustment was made since the strong development of wireless broadcasting can cause interference to the FM broadcasting systems across the country.

In addition, the adjustment is also aimed at preventing the penetration of undesired broadcasting waves that can be detrimental to the national security, Thu said.

However, only 25 percent wireless broadcasting stations nationwide can ensure their operation within the required band, he said.

Under current regulations, such a station must satisfy three criteria: firstly, its transmitter must meet required technical standards; secondly, the broadcasting must be within the regulated band; and the third, the station must obtain an operation license from a competent agency. 

In practice, many broadcasting stations are operating without meeting these criteria. Therefore, they often release interference causing radiation that is above the acceptable limits.

156, or 64 percent, of the 241 FM transmitters for wireless broadcasting systems examined by the Directorate from the third quarter of 2011 to the first quarter of 2012, were unqualified.

“We are very concerned about such a high rate,” Thu said.

The identification of an interference source for a specific information and communication system is a task that is difficult, expensive, and time consuming. Therefore, in a context that many unqualified or unlicensed stations remain operate randomly, the removal of interference sources is very difficult to do, he said. 

The Directorate blamed the interference on loose management over the quality of wireless broadcasting equipment. 

In addition, many local authorities have used wireless broadcasting systems without a license.

Source: Tuoi Tre