Reply to thread

Message

<blockquote data-quote="futumsch" data-source="post: 722263" data-attributes="member: 321089">Hi Vipersan, I have some experience with this quite regularly. Circular polarized LNBs do not need rotating for circular polarised signals. Rotating a whole circular polarised LNB body has no affect on signal strength on a circular polarised signal.If your 1.8m dish is on a polar mount, you just need to set the LNB vertical at your due south, and the linear polarised signals of the rest of the linear polarised birds (bar the Astra and Hot Bird satellites) will match your LNB's skew. If your 1.8m was on a Az/El mount, then the skew for a linear polarised LNB would need to be adjusted as you move your dish across the satellite arc, otherwise the LNB would still be in the vertical plane.I'm personaly not familiar with fitting a dielectric plate in LNB's for circular polarised reception (though I've read about it), but I would assume the dielectric plate doesn't care about the incoming signal, it needs to be set in relation to the tiny little antennas sticking up in the back of the throat of the lnb to seperate the left/right polarised signals.So once you have set your LNB skew for linear satellites, your assumption is right that the positioning of the dielectric plate in the LNB throat is all that matters.Just for completeness, the polarisation response of a linear LNB is slightly flat within a few degrees of it's optimal skew, and then drops off sharply to a 30dB+ null as it is rotated though 90degrees. This does not happen with a circular polarised LNB, your relying on the dielectric plate to give you the best cross polarisation isolation between LH and RH polarised signals.Hope I'm not teaching your granny to suck eggs, but its an interesting thread.</blockquote>

[QUOTE="futumsch, post: 722263, member: 321089"] Hi Vipersan, I have some experience with this quite regularly. Circular polarized LNBs do not need rotating for circular polarised signals. Rotating a whole circular polarised LNB body has no affect on signal strength on a circular polarised signal. If your 1.8m dish is on a polar mount, you just need to set the LNB vertical at your due south, and the linear polarised signals of the rest of the linear polarised birds (bar the Astra and Hot Bird satellites) will match your LNB's skew. If your 1.8m was on a Az/El mount, then the skew for a linear polarised LNB would need to be adjusted as you move your dish across the satellite arc, otherwise the LNB would still be in the vertical plane. I'm personaly not familiar with fitting a dielectric plate in LNB's for circular polarised reception (though I've read about it), but I would assume the dielectric plate doesn't care about the incoming signal, it needs to be set in relation to the tiny little antennas sticking up in the back of the throat of the lnb to seperate the left/right polarised signals. So once you have set your LNB skew for linear satellites, your assumption is right that the positioning of the dielectric plate in the LNB throat is all that matters. Just for completeness, the polarisation response of a linear LNB is slightly flat within a few degrees of it's optimal skew, and then drops off sharply to a 30dB+ null as it is rotated though 90degrees. This does not happen with a circular polarised LNB, your relying on the dielectric plate to give you the best cross polarisation isolation between LH and RH polarised signals. Hope I'm not teaching your granny to suck eggs, but its an interesting thread. [/QUOTE]

Verification