Hi all, Had a chance to run the Transmit Rejection procedure as outlined on Page 91 of the SDR1K Operating Manual Ver 1.8.0. No joy.
Setup was a dummy load connected directly to the 1K with 5 turns of copper wrapped around it to a my old HP8557A. With 0 db attenuation and a -40dm reference level, 5 watts output produced a signal 60db over noise. At that level, no image could be seen. Varying the phase and amplitude over the full range produced no discernable image. Just for grins, I switched to AM. The upper side band was right on the USB signal and the lower side band was the same magnitude. Back on SSB, diligent searching under the lower side band frequency showed no image. Switching to LSB showed no image where the USB signal had been. If the rejection were a nonlinearity it would perhaps show up at full power, but I wouldn't think it's a linearity issue. Running CW, not sure the problem would show up on the 8557, but the experiment might be illuminating... It seems strange that varying the amplitude and phase all over produced no image. Maybe a test setup problem? Further suggestions would be most welcome... Thanks in advance, vy 73's Rob AB7CF On Tue, 18 Dec 2007 18:11:54 -0600 "Gerald Youngblood \(FlexRadio Systems\)" <[EMAIL PROTECTED]> writes: > This sounds like you need to go through the transmitter image > rejection > calibration as defined in the SDR1k manual. The I/Q imbalance on > the SDR1k > will cause an image at 2X the CW pitch frequency away from the main > CW tone. > Gerald > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of > [EMAIL PROTECTED] > Sent: Monday, December 17, 2007 11:57 PM > To: [EMAIL PROTECTED] > Cc: flexradio@flex-radio.biz > Subject: Re: [Flexradio] Strange signal report > > > Hi Jim, > > Dave said: > > 1. My main signal sounded absolutely perfect > 2. There was a second "ghost" signal about 1Khz lower. > 3. On the "ghost" signal > a. He could not hear "ghost" dits > b. He could here like a click at the beginning and end of the > "ghost" dashes. > 4. Together the two signals made like a "clucking" noise. He'd > never > heard anything like it. > 5. The phenomena was very consistent > > My first thought was RF feed back through the line from the paddles > to > COM1 but using the keyboard via CWX the same phenomenon was present. > Of > course I could have still been getting feedback on 30 though I don't > on > any other band. My other thoughts are something to do with the > caution > in the notes on SVN 1829 or I haven't done a calibration since > before SVN > 1818 was released and I have now have an IQ imbalance on CW XMIT. > > Didn't have time to do any further on air testing today. But have > a > buddy about 6 miles away. So will try to get some reproducible > results > tomorrow. > > Hope this helps... > > vy 73's > Rob > AB7CF > > > On Mon, 17 Dec 2007 15:59:39 -0800 Jim Lux > <[EMAIL PROTECTED]> > writes: > > At 10:10 AM 12/17/2007, [EMAIL PROTECTED] wrote: > > >Hi all, > > > > > >Have been using Beta V1.10.4 SVN:1829 since it was released with > no > > known > > >problems. Just finished a Q with W0GMO on 30M. (Actually > first > > time > > >ever with the rig on 30.) > > > > > >Dave reports that the rig was actually transmitting two signals > 1 > > at S7 > > >on 10.12481 and 1 at about S1 on approximately 10.12381. > > > > > > So, exactly 100 kHz away and 36 dB down? Or might it be 96 kHz > > away? > > (which would be quite suspicious, since the sampling rate is > > probably > > either 48 or 96 kS/sec) > > > > What's your DDS IF (default is 9kHz.. in DDS box of setup form if > > "expert" is checked) > > > > > > > > What sort of receiver was Dave using? (and does it have a 50 kHz > > IF?) > > > > >He could only > > >hear the second signal as clicks at the beginning and end of the > > dashes. > > >Same was true whether using the paddles or the CWX keyboard. > > > > Hmm.. could it be a slight imbalance between I/Q for higher > (audio) > > > > frequencies? > > > > The sideband suppression can vary across the audio band. For > > instance, if one channel (L or R) had a bit more or less HF > rolloff > > > > (say, because the cable is slightly different, so different > > parasitic > > C) It's less likely across the RF band (the variation in > frequency > > is > > a smaller fraction of the center frequency. > > > > If you want to do some tests.. does it change as you change your > > frequency (in big or little steps)? > > > > Jim, W6RMK > > > > > > > > > > > _______________________________________________ > 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/
