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</o:shapelayout></xml><![endif]--></head><body lang=DE link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal><span lang=EN-US>Hi John, <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>some time ago I wrote a little paper for a SDR meeting explaining how easy MDS or noise figure can be determined without external instrumentation. As it’s in German language, so I’ll try a short guide:<o:p></o:p></span></p><p class=MsoListParagraphCxSpFirst style='text-indent:-18.0pt;mso-list:l0 level1 lfo1'><![if !supportLists]><span lang=EN-US><span style='mso-list:Ignore'>1.<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span lang=EN-US>Calibrate your S-Meter with an accurate signal source using the setting tool of PowerSDR.<o:p></o:p></span></p><p class=MsoListParagraphCxSpMiddle style='text-indent:-18.0pt;mso-list:l0 level1 lfo1'><![if !supportLists]><span lang=EN-US><span style='mso-list:Ignore'>2.<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span lang=EN-US>Select ‘SigAvg’ in the S-Meter settings and e.g. a SSB-bandwidth of 2400 Hz<o:p></o:p></span></p><p class=MsoListParagraphCxSpLast style='text-indent:-18.0pt;mso-list:l0 level1 lfo1'><![if !supportLists]><span lang=EN-US><span style='mso-list:Ignore'>3.<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span lang=EN-US>Terminate your RX socket (ATT = 0) with 50 ohms and read the MDS at the S-Meter in dBm<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>This value corresponds with the equation:<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal;text-autospace:none'><span lang=EN-US> Noise figure F dB = MDS dBm + 174 dBm – 10 log B dB<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal;text-autospace:none'><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal style='margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal;text-autospace:none'><span lang=EN-US>A typical result of a Hermes board on the 20m band was -131, 3 dBm @2400 Hz. That give a noise figure of <o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal;text-autospace:none'><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal style='margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal;text-autospace:none'><span lang=EN-US>F = - 131,3 dBm + 174 dBm – 33,8 dB = 8,9 dB<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal;text-autospace:none'><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal style='margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal;text-autospace:none'><span lang=EN-US>You can verifiy this result using the noise line of the Panadapter. In this case you have to calculate with the FTT bin width (Hz) and select ‘Average’ detector in the settings. <o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal;text-autospace:none'><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal style='margin-bottom:0cm;margin-bottom:.0001pt;line-height:normal;text-autospace:none'><span lang=EN-US>73, Helmut, DC6NY <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-US><o:p> </o:p></span></p></div></body></html>