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Occupied Bandwidth

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Sep 12th, 2008 at 2:57pm  
what is this Occupied Bandwidth in iBuilder? Is this the real bandwidth that it is going to occupied in the satellite bandwidth ?

How do we calculate the bandwidth when using the spread spectrum?

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Reply #1 - Sep 13th, 2008 at 2:09am  
Occupied BW is the actual MHz you are occupying on the Xponder.  If you change your symbol, info or transmission rate you can change that value in iBuilder. You can also change it if you change your modulation scheme.
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Reply #2 - Sep 13th, 2008 at 6:17pm  
Hi Mike,

thanks for the info.

Do you have the calculation sheet or formula for the info rate, tx rate, FEC, modulation, Spread Spectrum factors?
So with these factors input, i can calculate out the bandwidth required.

regards,
w
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Reply #3 - Sep 13th, 2008 at 9:25pm  
Do you have access to iDirects iNPT 8?  It is on the TAC website.
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Reply #4 - Sep 14th, 2008 at 4:00pm  
yes. I will try that.

thanks.

regards.
w
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Reply #5 - Oct 15th, 2008 at 9:21pm  
When using SS, an SF of 1 (or SF=1 which increases the unique word size which helps your remote stay locked) will give you no spreading and your occupied bandwidth will not change.  Once you change go SF=2 your occ bw will be doubled and SF=4 will quadruple your occ bw.  So a 256k data rate, 1.2 spacing, 1/2 BPSK, SF=4 will run you near 2.5MHz of occ bw.
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Reply #6 - Oct 16th, 2008 at 7:48am  
Hi,

that is the problem with spread spectrum...a lot of bandwidth is needed.

By the way can iDirect implement this 1/2 BPSK?

Regards,
w0w
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« Last Edit: Oct 16th, 2008 at 11:07pm by Admin1 »  
 
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Reply #7 - Oct 21st, 2008 at 2:08pm  
On the upstream it supports BPSK / .431 FEC and the downstream supports BPSK .431 or .49 FEC.  Spreading is only available with BPSK modulation.
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Reply #8 - Oct 22nd, 2008 at 11:42am  
If you are in the market to do spread spectrum then you more than likely have enough money to support the MHz required (if not you probably should be doing it to start with).

The main reason to use spread is to minimize PSD with the smaller apertures commonly found on moving platforms.
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