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New member Username: CanadecaPost Number: 7 Registered: Jul-06 | what is linear LNB??? |
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Silver Member Username: WoofyOntario Canada Post Number: 241 Registered: Feb-06 | C/P from LK Read all about it. Circular & Linear LNB's: What's the difference? -------------------------------------------------------------------------------- OK everyone, put your polarizing sunglasses on. What's the difference? Answer: About -3dB or half the signal level. Now take your sunglasses off. Notice how bright it is in here? The difference in brightness is an example of using the wrong lnb type. Circular and Linear polarization refer to the characteristics of the radio wave that is transmitted by the satellite towards your dish/LNB. Below are links to visual comparisons of Circular (Left or Right-hand) and Linear (Vertical or Horizontal) polarization. http://www.lyngsat.c o m/echo3.html Nimiq 2 @82.0°W http://www.lyngsat.com/nimiq2.html Nimiq 1/3 @91.0°W http://www.lyngsat.com/nimiq1.html EchoStar 6/8 @110.0°W http://www.lyngsat.com/110west.html EchoStar 7 @119.0°W http://www.lyngsat.com/echo7.html EchoStar 1/2 @148.0°W http://www.lyngsat.com/148west.html How do I know they are circularly polarized? If you click on any one of the links for the satellites above you will notice that under the first column labeled as "Freq. Tp" you will find one of the following single letter designations: "R" = right-hand (=circular polarization) "L" = left-hand (=circular polarization) So what about linear polarization? Linear polarization refers to a wave of radio signal rotating in a single plane. Think of an approaching helicopter as the helicopter's main rotor is moving towards you. It is rotating in a single, horizontal plane. The same approaching helicopter's smaller rear rotor is rotating in a single, vertical plane. In our satellite case it can be either in the "H"orizontal or "V"ertical plane. The following example satellites (visable in N.America) are transmitting with a linear polarized signal: SBS 6 @74.0°W http://www.lyngsat.com/sbs6.html AMC 5 @79.0°W http://www.lyngsat.com/amc5.html AMC 9 @85.0°W http://www.lyngsat.com/amc9.html IA 6 @93.0°W http://www.lyngsat.com/ia6.html IA 5 @97.0°W http://www.lyngsat.com/ia5.html AMC 1 @103.0°W http://www.lyngsat.com/amc1.html AMC 2 at 105.0°W http://www.lyngsat.com/amc2.html EchoStar 9 @121.0°W http://www.lyngsat.com/echo9ia13.html Again, under the first column labeled as "Freq. Tp" you will find one of the following single letter designations: "V" = vertical (=linear polarization) "H" = horizontal (=linear polarization) Now that you understand the difference between the two satellite polarization types please put your polarizing sunglasses back on. Hmmm, a little harder to read this right? Well, that's what happens to your receiver when you try to use a linear polarized LNB to receive a circular polarized satellite signal and vis-a-versa. About a 50% loss of signal! Armed with the invaluable information you now possess, by using this link http://www.lyngsat.com/america.html you can determine for yourself what type of LNB you will need for each satellite. If you need a circular polarized LNB look for words describing it as "DSS" or "DBS" or "circular" or a combination of these terms. If you need a linear polarized LNB look for words describing it as "FSS" or "FTA" or "linear" or a combination of these terms (FYI: All Universal LNB's are linear LNB's). -------------------------------------------------------------------------------- Quote: ...you could use linear LNB to get circular signal with 50% signal lost. You will need a large dish to compensate for this loss. Quote: ...you can't use circular LNB to get linear signal. Technically incorrect. Trying to receive linear polarized signals with a circular polarized lnb (antenna) is possible with the same 3dB/50% loss of signal. The actual reason why you most likely cannot receive linear signals with circular lnb's is because most all "DSS" circular polarized lnb's are incapable of receiving the frequecies at which linear FSS signals occur: Standard FSS LNB (11.7-12.2 GHz) -------->DSS LNB (12.2-12.75 GHz) Universal FSS LNB (10.7-12.75 GHz) <-- has wide bandwidth |
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New member Username: CanadecaPost Number: 9 Registered: Jul-06 | thanks for the info |
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Silver Member Username: WoofyOntario Canada Post Number: 242 Registered: Feb-06 | |
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Silver Member Username: WoofyOntario Canada Post Number: 243 Registered: Feb-06 |