Hi Rob, Based on your description, you either have a very bad ground loop between the SDR-1000 and sound card or the sound card has a problem. The Radio Shack ground isolators work reasonable well in this application for both transmit and receive.
Gerald Gerald Youngblood, K5SDR FlexRadio Systems Ph: 512-535-4713 Fax: 512-233-5143 Email: [EMAIL PROTECTED] Web: www.flex-radio.com > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Rob Dennison > Sent: Tuesday, October 23, 2007 7:22 PM > To: flexradio@flex-radio.biz > Cc: flexradio@flex-radio.biz > Subject: Re: [Flexradio] 11kHz DC noise > > Hi Jeff, > > Thanks for your tip on the ghosts. Performing the image > null manually > got rid of them. Let me explain, even with my HP RF gen, I > couldn't get PowerSDR to execute the RX Image Reject Cal > successfully. Thanks to your note I did some more searching > and found that I could manually set the > Receive Rejection Phase and Gain. (PowerSDR Setup>DSP>Image > Reject) > > That did it. Not only did it get rid of the images but it > also seems to have improved overall performance. > > BTW, the diagnostic message generated by > (General>Calibration>RX Image Reject Cal) doesn't give a clue > there is a way to do the compensation manually!! > > My 11kHz hump is 20dBm in magnitude and 1.2 Khz wide. Pretty > objectionable. I've responded to a couple of other mails on > the subject and will keep after it. I suspect PowerSDR is > written in some flavor of C. Being error prone, I've always > favored other programing languages otherwise I would be > tempted to take a shot at the code. ;o)~ > > Your tip on the rejection really improved the performance and > removed a major nuisance... > > Many thanks > Rob > AB7CF > > > On Sun, 21 Oct 2007 10:01:39 -0700 "Jeff Anderson" > <[EMAIL PROTECTED]> writes: > > Hi Rob, > > > > If you are seeing aliased ghosts below the hump, you might want to > > check that you've correctly nulled the image frequency - I > don't have > > the same ghosts you seem to have. Some experimentation should help > > you identify what the problem is - personally, I would > certainly find > > "ignoring" the lower part of the sprectrum below the hump much more > > objectionable than simply having the small bump at 11 KHz. > > > > Although I've never found the hump to be objectionable > (note that it's > > not just DC, but also low-frequency noise), if it's > bothering you and > > your friends you might want to try experimenting with ways > to mitigate > > it > > - no > > doubt you'd get tremendous praise from the list if you can find a > > reliable way to reduce or eliminate it! > > > > Best of luck! > > > > - Jeff, K6JCA > > > > -----Original Message----- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] Behalf Of Rob Dennison > > Sent: Sunday, October 21, 2007 4:19 PM > > To: flexradio@flex-radio.biz > > Subject: [Flexradio] 11kHz DC noise > > > > > > Hi guys, > > > > Have my SDR1k working well enough now to start tackling deeper > > problems. > > > > One of the first is the 11kHz DC noise. Quite a few of my friends > > have been through the shack now. They always ask about the > 11kHz hump > > and are always turned off by my Q10241 answer: "gotta live > with it." > > It is a real problem in selling them on flexRadio. They > look on it as > > a design defect. So do I. > > > > So having read and re-read Q10241 in the knowledge base I am still > > dissatisfied. Why do we have to live with it? It is a > design defect. > > > > 1. Okay on audio transformers but why not optical isolation? It > > seems optical isolators would have much wider bandwidth. > > 2. Also many of the peaks I see below the hump seem to be > aliased. > > This > > is confusing enough that I've made it a rule not to look below the > > hump. > > I don't want to waste air time clicking on ghosts. Why not > just start > > the panadapter spectrum display at the frequency > corresponding to dc? > > 3. If we have a good answer to 2, why not subtract (or otherwise > > process) out the DC hump? After all, we know what it is > and where it > > is. > > Yeh, I know there might be a signal big enuf to see > somewhere in the > > hump but tuning down band a bit will reveal it. > > 4. Still solution 3 seems to be in the nature of a work around. > > Why > > not rethink our algorithm chain? As flexRadio gets more > successful > > I > > can see the attack ads starting up. Think about the next QST > > review... > > Some competitor will solve the problem. > > > > Looking forward to some good answers to a real detractor to the > > flexRadio concept. > > > > Rob > > AB7CF > > > > _______________________________________________ > > 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/ > > > > > > > > > _______________________________________________ > 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/
