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#5
June 27th 15, 01:07 PM
posted to sci.electronics.design,rec.radio.amateur.antenna
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Antenna Amplifier Noise Figure
On 6/27/2015 7:48 AM, amdx wrote:
On 6/26/2015 9:46 PM, rickman wrote: On 6/26/2015 12:38 PM, amdx wrote: On 6/26/2015 7:24 AM, rickman wrote: I read this post in an antenna group and I don't get how this guy is coming up with a negative noise figure. Looks to me like he is calculating the noise figure of a resistor, not the amplifier. Anyone care to explain this to me? The part that seems bogus is this... The negative NF is defined as the amplifier noise being less than the increase in noise due to the amplifier gain. I thought noise figure was NF = SNRin / SNRout Rick I once ask Ratzlaff about the FSL antenna, in his comments he said, "high Q or low Q has little relation to how the FSL will actually perform for receiving weak signals.", but then went on to say, "Of course using Litz is the only type of wire to use." When I ask him about why Litz is important if Q isn't, he got ****ed off and wrote back, "When you make sarcastic replies to the info I passed along, and question what I say, then I write you off as just a tire-kicker, not interested in possibly learning something, and I have no interest in saying anything more." Seems to me he said something incorrect and didn't like having someone ask him to clarify it. I'll leave it to you to figure out which part was incorrect. I thought Q would be important, an FSL is a ferrite loaded tuned loop. With magic mixed in! ;-) If Q is not important, why use Litz? I suspect you might have already tried to ask him, and now he's mad at you too! Mikek I suspect he said he didn't like your sarcastic replies because you made sarcastic replies much more than he didn't want to discuss anything he said. I was not being sarcastic in my response when I ask about the Litz. Look at the larger picture. -- Rick |
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