Thanks, Dave. That helps. Connect the FLEX-5000 to a dummy load and see if you hear the distortion on another radio. If you don't (which is what I suspect), then you most likely have common mode RF currents on the coax connected to the F5K unless your shack in in the near field of the antenna and you are running some power and then it could be a contributing factor.
You have to remember that the SDR hardware *and* the PC make up the radio or as I like to refer to it as a radio system. With traditional radios like the ones you mentioned, all of the components that make up the system are in the same Faraday cage whereas the FLEX-5000A does not have this luxury. The FLEX-5000 itself is very immune to RFI. The interface between it and the PC are usually more susceptible to RFI. Adding ferrite beads to the Firewire cable can help, but you need to make sure that the PC and the SDR radio hardware have a good low impedance ground between them (http://kc.flexradio.com/KnowledgebaseArticle50370.aspx). Once you have the RF currents off of the Firewire cable which is what the PC to F5K low impedance ground accomplishes, then you need to deal with the RFI source which is the common mode currents on the coax shield. Grounding the coax shield and the proper use of choke baluns will do a good job of shunting the stray currents to ground. If you cannot ground your coax due to dwelling restrictions, then you may want to investigate using a counterpoise. The following is an excellent article on dealing with grounding http://kc.flexradio.com/KnowledgebaseArticle50426.aspx. One other cause of bad audio is not having the proper XP hotfixes installed. You can check that using this procedure making sure you do not have a SidSpeed error http://kc.flexradio.com/KnowledgebaseArticle50456.aspx You are using a PC that is at the bottom end of that which is recommended to run PowerSDR. You can try using lower sampling rates and larger audio buffer sizes as a too small buffer will cause distortion. Last but not least, you are running on an older beta version of PowerSDR. I would recommend that you upgrade to 2.0.16. It probably will not help with the distortion, but it will upgrade you to the latest firmware and software. -Tim -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of David Edwards Sent: Saturday, January 01, 2011 6:51 PM To: [email protected] Subject: [Flexradio] RF Feedback follow up info Forgot to mention Radio is Flex 5000, Power SDR v2.0.8, OS Windows XP Home on Pentium 4, 3 Ghz, 4 gb ram thanks de WB1S _______________________________________________ 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.flexradio.com/ Homepage: http://www.flexradio.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.flexradio.com/ Homepage: http://www.flexradio.com/
