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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="canofan" data-source="post: 512995" data-attributes="member: 259756"><p>I am using a feedhorn for the 11.7 to 12.2 ghz band with a Norsat 7706A and it is miracles above what I was using before.</p><p>However this feedhorn (CM3040645) has a round throat and I had to use a round to WR75 transition to make it work OK.</p><p>I cannot help thinking that, if I had a feedhorn with the same shape but with a rectangular throat (CM3040605), I could remove the transition, and its insertion loss, to achieve even better performance.</p><p>I think the transition introduces 15°K to the system noise. For Nilesat at our latitudes: a well setup antenna adds 30°K. Total noise 45°k which added to the 0.6db NF of the Norsat (45°K) is 90°k corresponding to 19.54dbk. By removing this 15°K caused by the transition we fall back to 75°K. corresponding to 18.75dbk making an improvement of 0.79db.</p><p>The difficult thing is that, when you order the longer single polarity feedhorn, you are not sure what you receive: will it be the round or the WR75 version?</p></blockquote><p></p>
[QUOTE="canofan, post: 512995, member: 259756"] I am using a feedhorn for the 11.7 to 12.2 ghz band with a Norsat 7706A and it is miracles above what I was using before. However this feedhorn (CM3040645) has a round throat and I had to use a round to WR75 transition to make it work OK. I cannot help thinking that, if I had a feedhorn with the same shape but with a rectangular throat (CM3040605), I could remove the transition, and its insertion loss, to achieve even better performance. I think the transition introduces 15°K to the system noise. For Nilesat at our latitudes: a well setup antenna adds 30°K. Total noise 45°k which added to the 0.6db NF of the Norsat (45°K) is 90°k corresponding to 19.54dbk. By removing this 15°K caused by the transition we fall back to 75°K. corresponding to 18.75dbk making an improvement of 0.79db. The difficult thing is that, when you order the longer single polarity feedhorn, you are not sure what you receive: will it be the round or the WR75 version? [/QUOTE]
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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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