I've read ,read on lnb's and the more I read some questions come up, because the linear does v/h polaraty it in theary will work on circular polarity r/L sats,but circular lnb's only on circular sat's. Is this correct? if so does it work well?
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.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:
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:
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.
So in theary yes,but 50% signal loss is not acceptable.Unless .....mmmmm...u have one motha of a big reflector plate but thats not reasable.Linear for linear sat and circular for circular. Thanks lk gonna save this in pc .
LK generalized the two distinct polarization in a simple way In theory let me add that with Linear LNB you can refer to Circular wave as two phases of linear Amplitude waves. Therefore with linear LNB you may be able to pickup some transponders. And vice versa. I'm not so sure about the +/-3 db that LK is refering to. It doesn't mean that I disagree. But I'm just offering a simple theoritical explaination on why you get 50% to 60% of of the two polarizations.