Sure Jim,
Regards the reference point, you have a valid point. But then let's reference the signal to an isotropic antenna for an absolute reference. Then a transmitting station will actually know how well he's doing. Otherwise all I give a hoot about is total link performance at my ear. Mebbe flexRadio should give us some controls for entering link losses under our control... To be truthful, I'm still not sure what's going on with my rig. I can definitely hear the preamp working. Maybe until it's calibrated powerSDR uses a fixed value for preamp gain.... I'll let everyone know the results. vy 73, it's always a pleasure Jim Rob AB7Cf On Fri, 25 Jan 2008 06:40:48 -0800 Jim Lux <[EMAIL PROTECTED]> writes: > 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/
