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<blockquote data-quote="mikethebike" data-source="post: 25131" data-attributes="member: 175983">Thanks for the fast feedback guys!Actually it seems that Rolf is closer to the mark (sorry Old Fred!).&nbsp; As a simple test I tried rotating the polariser by 90 deg whilst maintaining the LNB orientation.&nbsp; Result: all horizontal channels coming in loud and clear, vertical channels non-existent, i.e. the inverse of the previous problem!Clearly the polariser is the cause, but since I don't even know the make of the dish (bought secondhand via Ebay, and involving precarious dismantling on a Ravenna rooftop!) and there are no obvious markings anywhere, a feedhorn without polariser is not really on.&nbsp; I'll double check on this first of course, since it would be the easiest way.However, the alternative will be to find out more about polarisers and how they work.&nbsp; I know they can be used to give skew control for peaking weak signals, but this one (two wire) reads open-circuit to a meter.&nbsp; Anyone know any links giving basic technical information on polarisers?</blockquote>

[QUOTE="mikethebike, post: 25131, member: 175983"] Thanks for the fast feedback guys! Actually it seems that Rolf is closer to the mark (sorry Old Fred!). As a simple test I tried rotating the polariser by 90 deg whilst maintaining the LNB orientation. Result: all horizontal channels coming in loud and clear, vertical channels non-existent, i.e. the inverse of the previous problem! Clearly the polariser is the cause, but since I don't even know the make of the dish (bought secondhand via Ebay, and involving precarious dismantling on a Ravenna rooftop!) and there are no obvious markings anywhere, a feedhorn without polariser is not really on. I'll double check on this first of course, since it would be the easiest way. However, the alternative will be to find out more about polarisers and how they work. I know they can be used to give skew control for peaking weak signals, but this one (two wire) reads open-circuit to a meter. Anyone know any links giving basic technical information on polarisers? [/QUOTE]

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