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VSAT technology and installation >> Gilat VSAT Forum >> Help, Easy spectrum conversion
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Message started by tearepa13 on Dec 12th, 2011 at 1:54pm

Title: Help, Easy spectrum conversion
Post by tearepa13 on Dec 12th, 2011 at 1:54pm
Just trying to figure out this spectrum conversion in the Skyedge II. You put in the paramaters, for this example downlink RF is 12664 MHz, PLL LNB is 10.95-11.7GHZ (going by memory here), LO LNB 10GHZ. Now I thought taking away the LO from the RF down would be OK, but it seems I have to take the difference between 11.3 and 10 = 1.3, away from RF, and then that becomes the downlink freq...ie 11364
I'm no expert at this, but can someone please set me straight? I kind of worked it out by trial and error (of course its b/w 10.95-11.7), but I have no logical understanding why I got it.

Title: Re: Help, Easy spectrum conversion
Post by Eric Johnston on Dec 12th, 2011 at 2:03pm
Check your LNB by reading the label and find the actual model number and local oscillator frequency.

To receive a downlink carrier at 12664 MHz you need an LNB with LO=11.3 GHz so that the resulting output frequency from the LNB lies in the acceptable L band input tuning range of the modem, possibly 950 - 2150 MHz.  The upper end of the modem receive range varies according to the manufacturer and may, for example, be 1700, 1950 or 2050 MHz.

e.g.  12664 - 11300 =  1364 MHz.

Read more How an LNB works

Best regards, Eric.

Title: Re: Help, Easy spectrum conversion
Post by tearepa13 on Dec 12th, 2011 at 10:50pm
The LO is 10GHZ on the sticker, the model # sorry I don't have that info on me... it's part of Australia's NBN spot coverage off Ipstar 119.5 E(using Gilat gear). I've never seen 10 as an LO, usually 11.3, 10.6, 10.7....this is the part that confuses me when you apply the 11.3 calc, why would it say 10, Am I missing something obvious?
Trying to do a friend a favor who's learning the ropes.

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