Hi Gerald, Okay ran the level calibration using an HP8601. After running the calibration preamp behavior is as you described. A signal does stay at a constant level for all preamp gains and the noise floor drops appropriately.
As the skunk said when the wind changed: "now I remember I started out with V1.8 and when I first got the 1K going, I calibrated the levels but there was so much going on that I didn't recognize the change in behavior. Later when I migrated to V1.10.1, I didn't realize I had to copy the database. Later when I migrated to V1.10.3 I copied the database." Of course by that time I'd lost the calibration. Only problem is that the 0 Beat control is grayed out now. Being semi tone deaf I do use that a lot. Anybody got ideas on how to fix that? If anyone is still following the saga here the dummy load test results follow. Many thanks for all the help vy 73m Rob AB7CF After calibration test results: 80 Meters. AGC Fixed, 50 Ohm Dummy Load, CWL, 3.530Mhz, bw 25 Hz All measurements in dBm Preamp Meter Panadapter Off -102 -99 Low -111 -108 Med -124 -120 High -134 -129 20Meters. AGC Fixed, 50 Ohm Dummy Load, CWL, 14.033, bw 25 Hz All measurements in dBm Preamp Meter Panadapter Off -103 -98 Low -113 -108 Med -123 -121 High -133 -128 10Meters. AGC Fixed, 50 Ohm Dummy Load, CWL, 28.020, bw 25 Hz All measurements in dBm Preamp Meter Panadapter Off -102 -98 Low -112 -108 Med -122 -118 High -133 -128 On air testing appears to show that with atmospheric noise there is only a 10 dBm or so drop in the noise floor as the Preamp gain is varied. I must say tuned right this is the easiest to copy rig I've had. On Fri, 25 Jan 2008 19:57:27 -0600 "Gerald Youngblood" <[EMAIL PROTECTED]> writes: > Hopefully, I can shed a little light on this subject. Here are a few > facts: > > 1) Traditional "legacy" radios measure the AGC gain and convert the > gain to > S Units. I remember my old 706 that showed a higher S Meter reading > if I > turned the RF gain down, rendering the meter totally useless. The S > meter > readings would change if I turned the attenuator or preamp on/off. > That > means that the S meter was totally meaningless for measuring signal > strength > at the antenna terminals. > 2) The FlexRadio products measure the signal strength at the > antenna > terminals in the same way that a spectrum analyzer does. If you > change the > preamp settings, the noise floor goes DOWN and the signal level > stays the > same. Remember that when you change the preamp setting, you have > not > changed the signal level at the antenna terminal. You have, > however; > improved the signal to noise ratio with the preamp and therefore the > noise > should go down in reference to a fixed signal level. > 3) If you are using a SDR-1000 you must calibrate the radio using > an > external signal generator. If you move to a new version of the > software > with a new database, you must recalibrate on the 1000 unless you > import your > old database. > 4) If you are using a FLEX-5000, it is fully calibrated at the > factory and > the data is stored to EEPROM inside the radio. We you run the radio > for the > first time; it pulls the data from EEPROM into the PowerSDR > database. If > you delete the PowerSDR.mdb database, it will start fresh and pull > the data > in again. > 5) The FLEX-5000 with PowerSDR has built in test equipment (BITE) > that > allows everything in the radio except for the power/SWR bridge to > be > calibrated without external test equipment. In fact it is the same > method > used to calibrate in the factory. > > In summary, an accurate S Meter will give the same reading no matter > the > preamp, attenuator, or gain settings in the radio. If the preamp is > turned > on, the spectral noise floor should go down while the signal stays > the same > on the panadapter. > > Hope that helps, > Gerald > President > FlexRadio Systems > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Robert > Dennison > Sent: Friday, January 25, 2008 1:31 PM > To: [EMAIL PROTECTED] > Cc: FlexRadio@flex-radio.biz > Subject: Re: [Flexradio] gain on the sdr1000 > > 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/ > > > > _______________________________________________ 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/
