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DISH SETUP: Single sat, Multi-Sat & Motorised
Dual LNB ok Astra2/Hotbird - but not for all channels
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<blockquote data-quote="Terryl" data-source="post: 1031059" data-attributes="member: 369937"><p>Your correct about the L/R problems, L becomes R and R becomes L, and your right. it does not really affect a H/V polarity (that much), the main problems found with a Gregorian reflector type antenna was with two or more satellites close in, (under 8 degrees of arc) there were side lobe scatter problems and what was called multi bounce, this is where the signals from two or more sources bounced around between the reflectors and cause small phase cancellations, this was due to imperfections and alignment problems in the main and sub reflectors.</p><p></p><p>This is not a problem with a single satellite/LNB setup, but found to be a problem with multi signal setups, especially with signal sources coming in from different points along the receive axes, the closer the signal's were together the bigger the multi signal problems, this is why we never went with this style of antenna for CATV head end work, (we tried) but used single dishes and LNB's for each satellite, this is also why they try and make the transponders on adjacent satellites higher or lower in frequency and polarity. Had this style of antenna worked out for us it would have saved a ton of money for the extra dishes and the land to put them on.</p><p></p><p>On a single reflector type dish the signals reflected to the LNB that miss keep going, on a dual reflector type dish the signals that miss can be redirected back into the main (it's not a perfect world) by anything, it could be the mounting hardware for the LNB's it's self, this back scatter can raise the overall background noise on some transponders quite a bit.</p><p></p><p>Remember that these dishes have a very wide field of view and can pick up signals from about 40 degrees of arc, so it may not be the satellite directly on each side but the next one over.</p><p></p><p>Again too much coffee and my brain hurts trying to remember why we didn't use this type of dish......</p></blockquote><p></p>
[QUOTE="Terryl, post: 1031059, member: 369937"] Your correct about the L/R problems, L becomes R and R becomes L, and your right. it does not really affect a H/V polarity (that much), the main problems found with a Gregorian reflector type antenna was with two or more satellites close in, (under 8 degrees of arc) there were side lobe scatter problems and what was called multi bounce, this is where the signals from two or more sources bounced around between the reflectors and cause small phase cancellations, this was due to imperfections and alignment problems in the main and sub reflectors. This is not a problem with a single satellite/LNB setup, but found to be a problem with multi signal setups, especially with signal sources coming in from different points along the receive axes, the closer the signal's were together the bigger the multi signal problems, this is why we never went with this style of antenna for CATV head end work, (we tried) but used single dishes and LNB's for each satellite, this is also why they try and make the transponders on adjacent satellites higher or lower in frequency and polarity. Had this style of antenna worked out for us it would have saved a ton of money for the extra dishes and the land to put them on. On a single reflector type dish the signals reflected to the LNB that miss keep going, on a dual reflector type dish the signals that miss can be redirected back into the main (it's not a perfect world) by anything, it could be the mounting hardware for the LNB's it's self, this back scatter can raise the overall background noise on some transponders quite a bit. Remember that these dishes have a very wide field of view and can pick up signals from about 40 degrees of arc, so it may not be the satellite directly on each side but the next one over. Again too much coffee and my brain hurts trying to remember why we didn't use this type of dish...... [/QUOTE]
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DISH SETUP: Single sat, Multi-Sat & Motorised
Dual LNB ok Astra2/Hotbird - but not for all channels
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