Bronze MemberUsername: Crazy_greek
Post Number: 57
And all FTA Satellites are V & H.
Now tell me where I can find FTA that uses Circular LNB,s?
Gold MemberUsername: Lklives
Post Number: 4273
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.
Circular polarization refers to a wave of radio signal rotating in a spiral. This spiral can be rotating in either the clockwise ("R"ight-hand) or counterclockwise ("L"eft-hand) direction. Think of an approaching airplane as the plane's propellar is moving towards you.
The following example satellites (visable in N.America) are transmitting with a circular polarized signal:
EchoStar 3 @61.5°W http://www.lyngsat. com/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)...14V
"L" = left-hand (=circular polarization)...18V
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).......14V
"H" = horizontal (=linear polarization)....18V
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).
There are also LNB subtypes such as dual output or quad output. I won't go into that here because there are several discusions on this forum as well as a FAQ dealing with those subtypes. I suggest you use the excellent search feature as well as spend some time reading the all important "Sticky" threads.
You can take your sunglasses off now.
This is very useful information.
One more thing, you could use linear LNB to get circular signal with 50% signal lost.
But you can't use circular LNB to get linear signal.
...you could use linear LNB to get circular signal with 50% signal lost.
You will need a large dish to compensate for this loss.
...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
Silver MemberUsername: Mc_sunny
Post Number: 166
Bronze MemberUsername: Crazy_greek
Post Number: 65
Thanks for the above info.