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<DIV>Thank you all – its now clear – thank you very much</DIV>
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<DIV
style="FONT-FAMILY: 'Segoe UI'; COLOR: #000000; FONT-SIZE: 10pt">73<BR>Tony</DIV>
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<DIV style="font-color: black"><B>From:</B> <A title=scott.traurig@gmail.com
href="mailto:scott.traurig@gmail.com">Scott Traurig</A> </DIV>
<DIV><B>Sent:</B> Thursday, January 17, 2019 6:50 PM</DIV>
<DIV><B>To:</B> <A title=dc6ny@gmx.de href="mailto:dc6ny@gmx.de">Helmut
Oeller</A> </DIV>
<DIV><B>Cc:</B> <A title=prosdr@gmail.com href="mailto:prosdr@gmail.com">Tony
Hagen</A> ; <A title=hpsdr@lists.openhpsdr.org
href="mailto:hpsdr@lists.openhpsdr.org">hpsdr</A> </DIV>
<DIV><B>Subject:</B> Re: [hpsdr] NOISE FLOOR</DIV></DIV></DIV>
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<DIV dir=ltr>Tony,
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<DIV>Common rule of thumb: attenuator noise figure = attenuation. When the
attenuator comes before the first amplifier, as it does in most radios, its
noise figure will dominate the noise figure cascade analysis.</DIV>
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<DIV>You can easily demonstrate this by first applying enough attenuation to see
the noise floor rise a little (you have to make noise figure bad enough so it
becomes a factor). Then increase the attenuator by 10dB and you will see the
noise floor jump up approx. 10dB.</DIV>
<DIV> </DIV>
<DIV>See here for more on noise figure and noise figure cascade analysis. There
is a link there to a handy calculator that works a three stage Friis
equation:</DIV>
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<DIV><A
href="https://www.microwaves101.com/encyclopedias/noise-figure">https://www.microwaves101.com/encyclopedias/noise-figure</A><BR></DIV>
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<DIV>The preamp (the only amp!) gain in the 7000 and 8000 is 14dB. In the other
radios it is 20dB. In all cases the preamp noise figure is about 6dB.</DIV>
<DIV> </DIV>
<DIV>Lots of GREAT stuff at the Microwaves101 site, BTW.</DIV>
<DIV> </DIV>
<DIV>Also somewhat related:</DIV>
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<DIV><A
href="https://apache-labs.com/community/viewtopic.php?f=6&t=2463">https://apache-labs.com/community/viewtopic.php?f=6&t=2463</A><BR></DIV>
<DIV> </DIV>
<DIV>73,</DIV>
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<DIV>Scott/w-u-2-o</DIV>
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