Bob, Ray, Thanks for the explanations, I suspected it was something like that. I was a bit confused about exactly what demo mode was demoing. Since I don't have a soundcard in the list (and won't need one for the Flex-3000), I just ignored that part of the startup and left the selection at the default sound card, which is not actually in the machine. So the audio stream is coming from somewhere, and seems to be just pink noise. Good enough for a demo at least of the GUI.
It is curious though that I didn't see any mention of the 9khz artifact in the manual, and it doesn't appear in the screen shots (e.g., p49 of the new Flex-3000 manual). Perhaps it's there but down in the noise. I ordered a Flex-3000 because it triggered a sense of deja vu. Back in the mid-70s I worked on a project to have a computer understand hand-sent Morse, starting at the antenna, and be good enough to follow the activity in a traffic net. We used "almost direct conversion" also. The computers of the day cost about a million bucks, and ran at about 1.000 megahertz, so we had to use a commercial military-grade receiver (RS232 controllable) to "down-convert" to audio, which was then sampled (assembler code of course) with all work in a 25KHz band, which might contain dozens of CW signals. Not so different from the 100-200Khz with today's Flexes. Because of the computer limitations, we did all the DSP at audio, but it was still possible to do some neat stuff. E.G., the program could "fingerprint" a station by looking at both transmitter (strength, beam heading, chirp, hum, clicks, etc) and "fist" (dot-dash ratio, speed variance through a word, etc.) characteristics, and then scan the band to find a particular operator by comparing fingerprints of signals to fingerprints in a database from prior sessions. This made it possible, for example, to follow a station in a net as it went "up 10" to pass traffic. We got a lot of good fingerprint data by sampling the error output of a PLL (real, not digital), as well as the actual signal. With enough computer power, we could have run the program simultaneously on each signal in the passband - which is probably feasible given today's processors. Might be interesting today for DX chasing or contesting. Awaiting the UPS guy with the 3000..., /Jack K3FIV On Thu, 2009-04-30 at 00:14 -0400, Bob McGwier wrote: > If you are running the code in demo mode, and it is taking in stuff from > a typical sound card, that hump to the left of center is the 1/f noise > - DC junk in the sound card. You can see a hint of this in some Flex > 3000 and 5000 radios depending on the quality of your grounding, etc. > but on noisy bands, not much. > > This is the reason the power spectrum is not centered. We offset from > DC (0 Hz in a -Fs/2 , Fs/2 IF band where Fs is the sample rate) to > avoid the degradation from the noise at the center of the passband on > receive. On transmit, it makes almost no difference since it is so far > down. > > Bob > N4HY > > > > Jack Haverty wrote: > > My Flex-3000 hasn't arrived yet, but I see this same "phantom image" > > behavior running PowerSDR 18.0 in demo mode. It also occurred in prior > > version 16. I figured I'd wait for the actual radio since it might be > > an artifact of whatever demo mode does to create the band-noise. It > > looks like just a fairly steady carrier at the position you describe, > > and when you center on it, it's not there, but pops back up a fraction > > of a second later at the offset position. > > > > /Jack Haverty > > Point Arena, CA > > > > On Wed, 2009-04-29 at 20:44 -0400, Tim Ellison wrote: > > > >> When ever anyone has an issue, it is imperative that you tell what version > >> of PowerSDR you are using because without that info, there is no reference > >> point to start from. > >> > >> > >> > >> -Tim > >> > >> -----Original Message----- > >> From: [email protected] > >> [mailto:[email protected]] On Behalf Of Randy Emerzian > >> Sent: Wednesday, April 29, 2009 8:31 PM > >> To: [email protected] > >> Subject: [Flexradio] Flex 5000 Phantom Image on panadaptor dispaly > >> > >> Hello, > >> > >> I seem to have a phantom image of a modulated signal just to the left of > >> center. When I click on it to listen the dispay re-centers, and I hear no > >> audio in any mode. The Image re-apeard at the same location ( two lined > >> left of center) no matter what freq I am centered on. Any Ideas? > >> > >> Randy - KI6VAU > >> > >> > > > > > > > > _______________________________________________ > > FlexRadio Systems Mailing List > > [email protected] > > http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz > > Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ > > Knowledge Base: http://kc.flex-radio.com/ Homepage: > > http://www.flex-radio.com/ > > > > > > _______________________________________________ FlexRadio Systems Mailing List [email protected] http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
