Good try Al, reminds me on trouble with fans (and fan control circuits) that I had. IMHO it is advisable to use (aditional) some coils or ferrite beads in series with the resistors. And a pair of ceramic C's 47nF .. 220nFor so in paralel with the electrolitic capacitors to get a good low RF impedance. Shield the filter and the wires to the fan. Sometimes it is enough to filter only the + wire and connect - direct to a good chassis ground. 73 groeten Peter petervn(a)hetnet.nl <mailto:[EMAIL PROTECTED]> ; pa0pvn(a)hetnet.nl <mailto:[EMAIL PROTECTED]> ; pa0pvn(a)gmail.com ; pa0pvn(a)amsat.org .
________________________________ Van: [EMAIL PROTECTED] namens Al Verzonden: za 7-7-2007 19:33 Aan: [email protected] Onderwerp: [Flexradio] SDR-1000 Fan Noise ( Electrical ) I don't know if anyone else has noticed but the fan in my SDR-1000 produces a wide band buzzing noise in and near the 12 meter band. See linked screen shots. http://www.hamsdr.com/dnld.aspx?id=622 is my sdr-1000 with the fan running. The signal can be detected over a range of +- 1 mhz peaking near 25 Mhz. One of the strange things about this noise is that as you tune across the frequency the amplitude increases as you approach the peak frequency and then decreases, but the peak does not scroll across the panadapter display. ( suspect there may be some QSD common mode effects when the DDS is set near to 1/8 th the reference oscillator Frequency. ) When I replaced the original fan with a different one from another vendor, the noise was MUCH worse with significant noise on 12.5 and 50 mhz in addition to 25 mhz. The noise was also detectable one 6.2 and 3.1.. So I went back to the original Flex fan and installed a RC filter . http://www.hamsdr.com/dnld.aspx?id=623 is my SDR-1000 with the filter installed and fan running ( The picture is identical to my screen shot with the fan disconnected. The third link is the filter that I installed. http://www.hamsdr.com/dnld.aspx?id=624 As a side effect of installing this filter, the 0 I.F. hump ( center of screen with 0.5x) is reduced in amplitude and width on all frequencies. AL, K0VM _______________________________________________ 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/ -------------- next part -------------- An HTML attachment was scrubbed... URL: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/attachments/20070708/f09649f9/attachment.html _______________________________________________ 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/
