John, can you be a bit more specific as to what you did and what you used to do this. My unit seems to have more than its share of these "carriers". What about 10 meters? Any improvement there?
Many thanks Stan AH6JR On Friday 22 September 2006 05:06 am, [EMAIL PROTECTED] wrote: > Hi Folks, > > I just wanted to let you know about a modification I made to my > radio. DC1 is a switch mode converter that provides +/- 15 volts > for the instrumentation amplifiers IC6/7 on receive that interface > the QSD to the sound card. > > The DC/DC converter's internal oscillator free runs at ~120 kHz > and is very rich with odd harmonics, every 240 or so kHz, throughout > the HF range. > > This manifests itself as low level 'carriers' that drift around and > through receive frequencies. When the SRD is first powered up they > move quite fast, but after the unit has warmed up the move very, very > slowly through your QSO. > > These signals were about S4 on my SDR1000 in the 40M band and are easily > removed with the automatic notch. But, loving to tinker like I do I > removed the DC1 and soldered a 7 pin header in its place. I used a 1" x 2" > x 2", +/- 15v linear supply wired to the header. > > How's it work? Great! No more warbling tones from within the SDR. > > I wish I would have done more before and after testing. Now when I > connect the receiver to a dummy load, most of the bands are clear of > spurs with the noise floor at -153 dBm. I imagine that the fundamental > waveform (square wave?) of the DC/DC converter was putting an awful lot > of total integrated power into the QSD and mixing with other signals > there to increase the total spurs. > > It just keeps gettin' better. > > Regards, > John > k2ox > > > _______________________________________________ > 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 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 Homepage: http://www.flex-radio.com
