Rob, What was a signicant 11 kHz problem on my SDR-1000 (mainly due to my second-floor shack and lousy Central Texas ground) is nonexistent on my FLEX-5000A. Spurs? Yep, a few small ones I can see with the antenna connector terminated but deep in the noise with the antenna connected. I have a worse problem with RFI from my wireless router.
I suspect the problem is more mechanical than software, attacking it from that end might bear fruit. You might check with KM0T (and take a look at his website at http://www.km0t.com/pages/sdr.htm). He has done quite a few major mechanical mods. Also, PowerSDR is open-source and anyone is welcome to try their hand at improvements. 73, Bob K5KDN -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Rob Dennison Sent: Sunday, October 21, 2007 6:19 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/
