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Check out this document:

http://cp.literature.agilent.com/litweb/pdf/5952-1147.pdf

You are confusing recevier NF with antenna noise temperature, which includes the effects of the sky temperature when determining an estimate for the total noise power in the receiver's frequency and BW. As you know, system noise temperature is a function of the ambient (sky) temp, lossless antenna noise temp, LNA noise figure (our variable here), the line loss between the antenna and the LNA, transmission line temp, and the missmatch (VSWR).

Now, the net signal/ noise ratio with 11 meter antenna connected (versus a 50 ohm load) will be impacted as the noise pours in at 11 meters. It may be that in my quiet environment and launch angle, that I'll notice an improvement, regardless of the improvement the analyzer shows in the shop. I'm using a vintage (1975) HP spectrum analyzer.

The Hfe of the replacement transistor is higher, but some have thought that this meant an overdrive condition (higher AC voltage) of the following state. That's not going to occur, but the front end is going to draw less current from the proceding tank circuit. That will cause a small missmatch in the impendance of the 1st amplificaiton stage (with the 2sc2999e) and the stage before it, since the input impedance is higher on it now, but the reduced noise floor that came along could still provide a net MSD improvement. That's what the test is about.

<blockquote data-quote="KG6YGE" data-source="post: 410198" data-attributes="member: 28834">Check out this document:<a href="http://cp.literature.agilent.com/litweb/pdf/5952-1147.pdf" target="_blank">http://cp.literature.agilent.com/litweb/pdf/5952-1147.pdf</a>You are confusing recevier NF with antenna noise temperature, which includes the effects of the sky temperature when determining an estimate for the total noise power in the receiver&#039;s frequency and BW. As you know, system noise temperature is a function of the ambient (sky) temp, lossless antenna noise temp, LNA noise figure (our variable here), the line loss between the antenna and the LNA, transmission line temp, and the missmatch (VSWR).Now, the net signal/ noise ratio with 11 meter antenna connected (versus a 50 ohm load) will be impacted as the noise pours in at 11 meters. It may be that in my quiet environment and launch angle, that I&#039;ll notice an improvement, regardless of the improvement the analyzer shows in the shop. I&#039;m using a vintage (1975) HP spectrum analyzer.The Hfe of the replacement transistor is higher, but some have thought that this meant an overdrive condition (higher AC voltage) of the following state. That&#039;s not going to occur, but the front end is going to draw less current from the proceding tank circuit. That will cause a small missmatch in the impendance of the 1st amplificaiton stage (with the 2sc2999e) and the stage before it, since the input impedance is higher on it now, but the reduced noise floor that came along could still provide a net MSD improvement. That&#039;s what the test is about.</blockquote>

[QUOTE="KG6YGE, post: 410198, member: 28834"] Check out this document: [url]http://cp.literature.agilent.com/litweb/pdf/5952-1147.pdf[/url] You are confusing recevier NF with antenna noise temperature, which includes the effects of the sky temperature when determining an estimate for the total noise power in the receiver's frequency and BW. As you know, system noise temperature is a function of the ambient (sky) temp, lossless antenna noise temp, LNA noise figure (our variable here), the line loss between the antenna and the LNA, transmission line temp, and the missmatch (VSWR). Now, the net signal/ noise ratio with 11 meter antenna connected (versus a 50 ohm load) will be impacted as the noise pours in at 11 meters. It may be that in my quiet environment and launch angle, that I'll notice an improvement, regardless of the improvement the analyzer shows in the shop. I'm using a vintage (1975) HP spectrum analyzer. The Hfe of the replacement transistor is higher, but some have thought that this meant an overdrive condition (higher AC voltage) of the following state. That's not going to occur, but the front end is going to draw less current from the proceding tank circuit. That will cause a small missmatch in the impendance of the 1st amplificaiton stage (with the 2sc2999e) and the stage before it, since the input impedance is higher on it now, but the reduced noise floor that came along could still provide a net MSD improvement. That's what the test is about. [/QUOTE]

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