APEX2014: Are satellite antennas a danger to ground staff?

A typical Ku-band antenna.
A typical Ku-band antenna.

Ed Mantiply, Physical Scientist, Federal Communications Commission (FCC), looked at concerns over RF exposure and safety issues at an Apex educational session in Anaheim.

He explained that there are human RF exposure guidelines published by the FCC, and tools available to aid in the analysis of RF exposure. In addition he looked at an example of the calculation of the RF exposure limits for a fictional aircraft Ku-band satellite installation.

Mantiply said that since in-flight internet access has taken off there are a lot of Ku-/Ka-band radio transmitters being installed on aircraft.

With this proliferation there has been an increase in the concerns of the health implications of human exposure to radio frequency energy.

Mantiply said that the key measurement is the specific absorption rate (SAR) – how much energy does the body absorb from radio transmissions. He also went through how tests on rats in the past help us derive the current limits.

He said that some mobile phones come close to the FCC limits when held close to the ear.

Mantiply then spent time explaining the various technical terms used in the RF exposure business, before showing that for a typical Ku-band antenna system, the “safe distance” is about 14.1m (46ft 3in).

Therefore, it would not be a good idea to be directly in front of a Ku-band antenna when it is running, if you were closer than about 40-46 feet. He said the “spillover” of RF energy from an antenna to ground crew should be way lower than the current safety limit.

Within the aircraft, passengers will be shielded by the metal skin of the aircraft (the so-called Faraday cage effect). Wave guide and cabling to the antenna would also be screened, making the risk minimal. However, he said he was unsure how this shielding would work with composite fuselages

With some airlines now operating Ku-band connections gate-to-gate there could be concerns that airport staff could be exposed, but Mantiply said that this would likely be below safety limits and be very short term.

He restricted his talk to the specified safety levels linked with RF heating at microwave frequencies. He said that current safety studies show that while there are no known links between microwave exposure and cancer and other diseased, studies are still ongoing. He also said the US government was currently looking at a review of both limits and guidelines.

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