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: [email protected] 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 [email protected] 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 [email protected] 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/
