Edwin, What you are saying is what I saw also, until I ran the calibration, then I got the results expected. I'd run the calibration and see if that changes your results. Phil K3TUF
Edwin Marzan wrote: > What I hear is what I expected. What I see on the scope is not what I > expected. Looks like the noise floor is dropping as the preamp is > engaged. The noise floor drops and the signals appear to pop out of > the noise. I wish the preamps in my other transceivers worked like that! > > > > Edwin Marzan > AB2VW > > > Date: Fri, 25 Jan 2008 06:40:48 -0800 > > From: [EMAIL PROTECTED] > > To: [EMAIL PROTECTED] > > CC: [EMAIL PROTECTED]; flexradio@flex-radio.biz > > Subject: Re: [Flexradio] gain on the sdr1000 > > > > Quoting Robert Dennison <[EMAIL PROTECTED]>, on Thu 24 Jan 2008 > 09:08:37 PM PST: > > > > > Hi Ken, > > > > > > Now I'm confused. Must have something calibrated wrong or a bad 1K. > > > > > > My SDR1K is sitting on 7.010. Nothing but noise. Keeping AGC-T > > > constant: with Preamp Off the noise level reads -105dBm peak. Now if I > > > put the Preamp on Low the noise level jumps to -94dBm and when I > put the > > > Preamp on Med the noise level jumps to -88dBm. Finally putting the > > > preamp on High the noise level jumps to -80dBm. > > > > > > To me that's what I would expect from a preamp. In fact first time > I saw > > > it, I said to myself "now that's the way a preamp should work!" > > > > Not really... As you say, you're thinking in terms of the display > > reading what comes out of the analog section. But, really, you want > > the display to be reading what's at the antenna terminals (just like a > > lab spectrum analyzer). So, you adjust the scale according to how > > much gain there is. > > > > That way, an input signal of a fixed amplitude (e.g. at -100dBm) is > > always displayed at the same amplitude. The behavior you describe > > (measured noise floor getting bigger as amplifier gain is increased) > > is sort of upside down (Unless the amplifier is really noisy?) > > > > Is there something else going on? > > > > With a fixed level input signal, does the SNR stay the same? (i.e. the > > preamp isn't contributing significant noise) > > > > > > > > _______________________________________________ > > FlexRadio Systems Mailing List > > FlexRadio@flex-radio.biz > > http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz > > Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ > > Knowledge Base: http://kb.flex-radio.com/ Homepage: > http://www.flex-radio.com/ > > > > > ------------------------------------------------------------------------ > Helping your favorite cause is as easy as instant messaging. You IM, > we give. Learn more. > <http://im.live.com/Messenger/IM/Home/?source=text_hotmail_join> _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kb.flex-radio.com/ Homepage: http://www.flex-radio.com/
