Do you have averaging turned on with the Panadapter? The S meter will display the highest value it sees for the samples (bins) it is analyzing. Within that sample of data it is analyzing, there are noise peaks that correspond to the higher value you are seeing (-117 dB rather than the -145 dB). I use the average of the noise floor, or what the Panadapter shows when averaging is on to determine what the noise floor is.
-Tim ---- -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Doug McCormack Sent: Thursday, June 14, 2007 11:30 AM To: flexradio@flex-radio.biz Subject: [Flexradio] Noise Floor S meter vs Panadapter I recently build the Elecraft kit to provide a reference signal for calibration of my SDR1000. With the 50 uV reference my S meter shows -73 dBm (S 9.0). At 1 uV reference, the meter shows -107 dBm ( S 3.3). These two numbers show the S meter is perfectly calibrated. When I remove the Elecraft unit and no antenna is connected, the meter shows a noise floor of -117 dBm (S1.3). But the panadapter shows -145 dB. I wonder why the panadapter does not agree with the S meter. Maybe I am should ground the antenna connector when measuring noise floor? When people ask me about the noise floor, do I say -117 or -145? I have always suspected my 5 year-old Dell 1.8 Ghz has high internal noise possibly on the PCI bus. Perhaps this Dell system noise is getting into my M44 sound card. I hope to have a new dual-core Intel computer later this week. 73, Doug VE3EFC -------------- next part -------------- An HTML attachment was scrubbed... URL: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/attachment s/20070614/d3f5da98/attachment.html _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ FlexRadio Homepage: http://www.flex-radio.com/ _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ FlexRadio Homepage: http://www.flex-radio.com/
