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Thread: Cell Phone output power?

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  1. #1

    Default Cell Phone output power?

    I searched the net but couldn't find a conclusive answer. Some say 1 watt others say 250mW. Who knows for sure?
    Thanks!

  2. #2
    Join Date
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    Default

    Contemporary 'digital' mobile phones in Europe operate using the GSM (Global Systems Mobile) system. There are two frequency bands allocated to GSM mobile phones, one at 900MHz, and one at 1800MHz. GSM uses a combination of frequency division multiple access (FDMA) and time division multiple access (TDMA). What this means in reality is that within each band there are a hundred or so available carrier frequencies on 200kHz spacing (the FDMA bit), and each carrier is broken up into time-slots so as to support 8 separate conversations (the TDMA bit). Correspondingly, the handset transmission is pulsed with a duty cycle of 1:8; and the average power is one eighth of the peak power. Once a call is in progress, the phones are designed to reduce the radiofrequency (RF) output power to the minimum required for reliable communication - under optimum conditions, the power can be set as low as 20mW (one hundredth of full power). Battery consumption and radiation output of the handset is further reduced by using 'discontinuous transmission' (DTX); the phone transmits very much less data during pauses in the conversation.
    http://www.techmind.org/gsm/

    So the max power output is 2 watt.
    But the phone constantly tries to use the lowest power needed for a reliable connection.
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  3. #3

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    Quote Originally Posted by PA5COR View Post
    But the phone constantly tries to use the lowest power needed for a reliable connection.
    i.e. the cellphone base station tower tells the remote cellphone what power to transmit, minimum close to the tower, maximum in a fringe area.
    73, Cecil, www.w5dxp.com
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  4. #4

    Default depends

    Quote Originally Posted by W5DXP View Post
    i.e. the cellphone base station tower tells the remote cellphone what power to transmit, minimum close to the tower, maximum in a fringe area.
    It depends upon the technology and frequency band. The first US standard - AMPS - had a 0.6w limit at 800 MHz. It was lower at 1.8 GHz.

    CDMA power levels are typically 10 db lower than the levels used for GSM or US TDMA. In city environments, your phone could be running at the milliwatt level, depending upon your location and how many users are trying to share the same cellsites.

  5. #5

    Default

    Quote Originally Posted by N4CD View Post
    It depends upon the technology and frequency band. The first US standard - AMPS - had a 0.6w limit at 800 MHz. It was lower at 1.8 GHz.

    CDMA power levels are typically 10 db lower than the levels used for GSM or US TDMA. In city environments, your phone could be running at the milliwatt level, depending upon your location and how many users are trying to share the same cellsites.
    This is exactly correct. I've never seen a modern cell phone that could generate 2 Watts, even peak. We've measured both current drain and e.r.p. on an outdoor 10m range using calibrated antennas (+/- 1 dB overall accuracy) to determine actual power as closely as possible when licensing many of these devices and everything indicates about 300mW peak for the typical phone, with average power being considerably lower. The e.r.p.s are actually lower than this since the antennas have less than unity gain.

    If the phone could provide 2W output even 1% of the time, the battery pack would not last long at all; on the contrary most hand held miniature phones provide 48 hours of standby and 3 hours of talk time, which based on the typical battery pack capacity would indicate that even "talking," they're usually running less than 100mW.

    WB2WIK/6

  6. #6
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    Maximum possible power output of a handheld cellular phone is 0.6 watts.
    Like others have posted, the system controls the actual output of the phone and it is typicially much less than that, usually less than 100 milliwatts. The carriers utilize tower top amplifiers to boost the receive signal and make up for any losses in the transmission line leading to the receivers in the base stations so high power from the handheld device is rarely needed.
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