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Re: [TowerTalk] Cellular Base Station Power Levels

To: Dave Fuller <rfcdma@spinn.net>,Jim Brown <jim@audiosystemsgroup.com>
Subject: Re: [TowerTalk] Cellular Base Station Power Levels
From: Jim Lux <jimlux@earthlink.net>
Date: Thu, 12 May 2005 15:25:29 -0700
List-post: <mailto:towertalk@contesting.com>
At 12:25 PM 5/12/2005, Dave Fuller wrote:
>For the PCS frequencies the max transmitter power is 8 or 15 watts
>depending on the equipment per carrier.  Antenna gain is typically 16 to
>18 dBi per sector.  Usually 3 sectors.  The average power usually runs
>about a fifth to tenth of that.    Most systems have at least 2 carriers
>(wideband channels) per sector and some as many as 5 carriers in a busy
>market.
>
>For 15 watts max per sector per carrier  you have  41.7 dBm to antenna
>maybe 1.5dB   min feedline and connector loss  and 17 dBi for antenna
>which gives you
>57.2 dBm.  This is 524 watts per sector per carrier at max output
>power.  Remember the power output of todays CDMA carriers for both
>cellular and PCS is widely variable based on traffic loading.  I would
>say you could have an average over the day of 1/5 the max output which
>puts you right at 100W per sector per channel.

But, for EMI purposes, you really can't time average, like you can for RF 
safety analysis.  The interference will be from the peak levels, so you'd 
really have to figure on 5 carriers at 524 W ERP worst case.

CDMA systems do spread the signal out over a wider bandwidth, which is 
helpful.  I suspect that TDMA systems will be the worst from an 
interference standpoint because of their high peak/average ratio. (the RF 
safety and cell phone battery life issues are more average power limited)


>   Typical sector
>beamwiths (hoizontal) on those antennas are 65 degrees at 3dB points.
>The vertical beamwidth is only 3 degrees or less and often the antenna
>is downtilted to keep interference from adjacent cells or cells on the
>horizon.   The design of CDMA systems is an exercise in interference
>management.

Useful information.



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