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andrishev
Joined: 05 Mar 2006
Posts: 39
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 13 Oct 2006 15:27 link budget analyses a question |
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Why the( SSPA )amplifier power is not included to these formulas?
received signal=(transmitter power)+(transmitter antenna gain)-(transmitter cab and conn losses)-(free space path loss+receiver antenna gain)-(receiver cable and con losses)
Why???  
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jmulchin
Joined: 13 Apr 2004
Posts: 3
Helped: 3
Location: Southern California
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13 Oct 2006 17:01 Re: link budget analyses a question |
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| It is. The transmit power refered to in the formula is the power output of your SSPA in dBm. The formula you show is the typical one used to calculate freespace path loss between two locations.
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andrishev
Joined: 05 Mar 2006
Posts: 39
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13 Oct 2006 17:04 Re: link budget analyses a question |
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will i add transmitter power out with SSPA out
TX power =transmitter 1dB compression point(transmitter output power)
or
TX power =transmitter 1dB compression point(transmitter output power)+SSPA output power
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jmulchin
Joined: 13 Apr 2004
Posts: 3
Helped: 3
Location: Southern California
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13 Oct 2006 17:22 Re: link budget analyses a question |
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| The only value you need is the total output power going to the antenna in dBm. Measure the final power output of your transmitter chain, the end that goes to your antenna, and use that value as the final power value for the formula. The 1db compression point value can be used if you like, or the linear value (before 1db compression point) can also be used. It won't make that much difference to the final answer.
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andrishev
Joined: 05 Mar 2006
Posts: 39
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13 Oct 2006 17:30 Re: link budget analyses a question |
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do you know any web page or book or software for link budget analyses
especially long range 200km LOS Ku,C or X band systems
Also satellite communication systems
With high data rate like 45Mbps
i am working on UAV unmanned air vechile2s data links
so i need high data rate ;long range; high frequency
i must downlink video from airborne and also i have size and power limitations on airborne i must make link budget analyses so carefuly
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jmulchin
Joined: 13 Apr 2004
Posts: 3
Helped: 3
Location: Southern California
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13 Oct 2006 17:41 Re: link budget analyses a question |
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In my first message I made a mistake and refered to the answer you get as the freespace loss. Your answer will be the received signal strength in dBm instead. Sorry for the mistake. Also, the formula for calculating the pathloss in dB is:
Loss (dB) = 32.4 + 20log(distance in miles) + 20log(freq in Mhz)
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andrishev
Joined: 05 Mar 2006
Posts: 39
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13 Oct 2006 17:52 Re: link budget analyses a question |
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| thank you
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Google
AdSense
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13 Oct 2006 17:52 Ads |
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RFDave
Joined: 18 Feb 2004
Posts: 346
Helped: 45
Location: NE USA
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14 Oct 2006 4:11 Re: link budget analyses a question |
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Try googling for Path loss analysis. Somewhere on the net is a path loss analysis for the Mars Pathfinder mission that you might find instructive. Excel is the tool I'm seen most used for this, so try filetype:xls at the end
Dave
www.keystoneradio.com
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