Are We Alone – Cell Phone Danger: Devra Davis

by Gary Niederhoff on December 21, 2010


Part 4 of Skeptic Check: Cell Phone Danger, featuring Devra Davis, scientist, and author of Disconnect: The Truth About Cell Phone Radiation, What the Industry Has Done to Hide It, and How to Protect Your Family.
(TRT 11:08)

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avatar Phil January 18, 2011 at 8:24 pm

Devra Davis draws a distinction between analog and digital phones because the analog phones transmit continuously while the digital phones transmit in pulses.

This is true only for GSM digital phones. The pulses arise because GSM uses “TDMA” – Time Division Multiple Access – to share each channel among up to 8 users. Each phone’s transmitter rapidly switches on and off at about 216 Hz so that they can take turns.

CDMA phones do not do TDMA. They all transmit continuously on the same channel, each with a different “spreading code” that allows the base station to separate them. (The transmitter does turn off when not needed, such as during pauses in speech.)

For CDMA to work, the mobiles must continuously control their transmit power levels so that their signals all arrive with equal strengths at the base station. This results in far lower average transmitter power levels than in GSM. It is not uncommon to see CDMA phones transmitting less power than they’re receiving from the base station!

Because CDMA phones operate at such low power levels, they are far less likely than GSM phones to cause radio frequency interference (RFI) to unshielded electronic equipment such as audio systems. The characteristic buzz of an interfering GSM phone has become a familiar sound in public address systems and on talking-heads TV news shows but I have yet to detect a case of RFI from a CDMA phone “in the wild”, i.e., outside of a test lab.

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