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Satellite TV receivers & systems support forums
DISH SETUP: Single sat, Multi-Sat & Motorised
Norsat LNB Whats Wrong ? pics
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<blockquote data-quote="ouagadougou" data-source="post: 500787" data-attributes="member: 187470"><p>That may well be (dont have 1 in front of me) but the dual pol transition has more insertion loss than a straight connection to a single LNB. VSWR does not not necessarily have any direct relationship to insertion loss and the dual pol transition definately has insertion loss. This insertion loss will always mean that the dual pol solution will perform worse than a single pol solution alone. Insertion loss before the LNB increases the effective system noise temperature more significantly than the value of the insertion loss itself because the system noise temperature is increased disproportionately to the insertion loss itself.</p><p></p><p></p><p></p><p>True the dual flange/dual pol transition acts as a polarisation filter but its the insertion loss it introduces that results in reduced overall sensitivity. I wouldnt worry too much about VSWR in a receive only system as system noise temperature is the overiding concern and any loss before the LNB input will result in lower receive sensitivity. None of these rx waveguide systems have tuning screws in the receive branches so none of them are VSWR optimised.</p></blockquote><p></p>
[QUOTE="ouagadougou, post: 500787, member: 187470"] That may well be (dont have 1 in front of me) but the dual pol transition has more insertion loss than a straight connection to a single LNB. VSWR does not not necessarily have any direct relationship to insertion loss and the dual pol transition definately has insertion loss. This insertion loss will always mean that the dual pol solution will perform worse than a single pol solution alone. Insertion loss before the LNB increases the effective system noise temperature more significantly than the value of the insertion loss itself because the system noise temperature is increased disproportionately to the insertion loss itself. True the dual flange/dual pol transition acts as a polarisation filter but its the insertion loss it introduces that results in reduced overall sensitivity. I wouldnt worry too much about VSWR in a receive only system as system noise temperature is the overiding concern and any loss before the LNB input will result in lower receive sensitivity. None of these rx waveguide systems have tuning screws in the receive branches so none of them are VSWR optimised. [/QUOTE]
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DISH SETUP: Single sat, Multi-Sat & Motorised
Norsat LNB Whats Wrong ? pics
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