Hi Scott, Your numbers are certainly very different than mine. I think I have a calibration problem and perhaps a problem with the 10db preamp. However, in switching to PowerSDR versions along the way I almost certainly have lost my Level calibration. This evening I'll haul the trusty HP signal generator in and do a calibration. Then we should see clearly what's up. I do fear the 10db preamp is dead. The risk taken in buying a used 1K.
vy 73 Rob AB7CF On Fri, 25 Jan 2008 12:35:06 -0500 "KQ8RP" <[EMAIL PROTECTED]> writes: > > My readings from 20 CW into dummy loadat 1K > > RX Meter Pan Display > Preamp Off -109 dBm. -109 dBm > Preamp Low -118 dBm -117 dBm > Preamp Med -132 dBm -131 dBm > Preamp High - 132 dBm -140 dBm > > at 25 HZ > > RX Meter Pan Display > Preamp Off -99 dBm. -110 dBm > Preamp Low -109 dBm -117 dBm > Preamp Med -122 dBm -131 dBm > Preamp High - 142 dBm -140 dBm > > > Scott Gordon > http://www.kq8rp.us > > ----- Original Message ----- > From: "Robert Dennison" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Cc: <flexradio@flex-radio.biz>; <[EMAIL PROTECTED]> > Sent: Friday, January 25, 2008 12:13 PM > Subject: Re: [Flexradio] gain on the sdr1000 > > > > Hi Eric, > > > > Well, I'm sure with antenna on the preamp output is noise floor > + > > amplified (atmospheric noise + signal.) > > > > With the dummy load while on 20M CW, I get the following RX Meter > and > > Panadapter noise readings. (Panadapter readings are eyeball of > course.) > > Also I'm taking the RX readings on noise with the 25 Hz CW > filter. > > > > RX Meter Pan Display > > Preamp Off -117 dBm. -115 dBm > > Preamp Low -117 dBm -117 dBm > > Preamp Med -125 dBm -123 dBm > > Preamp High - 125 dBm -125 dBm > > > > Readings would be constant except for that step between Low and > Medium... > > > > vy 73 > > Rob > > AB7CF > > > > > > > > > > > > On Fri, 25 Jan 2008 10:41:56 -0600 "Eric Wachsmann" > <[EMAIL PROTECTED]> > > writes: > >> Could this be due to atmospheric noise? Have you tried this on > a > >> dummy > >> load? > >> > >> > >> Eric Wachsmann > >> FlexRadio Systems > >> > >> > -----Original Message----- > >> > From: [EMAIL PROTECTED] > >> [mailto:[EMAIL PROTECTED] > >> > radio.biz] On Behalf Of Robert Dennison > >> > Sent: Friday, January 25, 2008 10:29 AM > >> > To: [EMAIL PROTECTED] > >> > Cc: [EMAIL PROTECTED]; flexradio@flex-radio.biz > >> > Subject: Re: [Flexradio] gain on the sdr1000 > >> > > >> > Hi Jim, > >> > > >> > Well, yes t'would be nice to have the panadapter display the > input > >> to the > >> > preamp, but mine displays the output from the preamp. > >> > > >> > Clearly the signal is amplified by the same gain as the > noise... > >> In my > >> > case as I increase the preamp gain a notch the noise level is > >> amplified > >> > by say 5db and the signal magnitude floating on top of the > noise > >> is > >> > amplified by the same amount. RX Meter with Sig Avg shows the > >> same > >> > result. Also, near as I can tell by ear and eye the preamp is > not > >> adding > >> > additional noise. > >> > > >> > Near as I can tell from the panadapter and RX Meter, my preamp > is > >> working > >> > like a near perfect linear amp. > >> > > >> > Yes, powerSDR, having some idea what the preamp gain, is can > back > >> it out > >> > of the display, but I've run every version of PowerSDR from 1.8 > to > >> 1.10.3 > >> > and they work exactly the same as I've described and measured. > I'm > >> now > >> > running SVN: 1917 and it's behaving as I described. > >> > > >> > Have I found a weird display mode? I'm too good at that for > my > >> own > >> > good... > >> > > >> > vy 73 > >> > 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/ > >> > >> > >> > >> > > > > > > _______________________________________________ > > 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/ > > > > > _______________________________________________ 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/
