The bottom line is that using the same mic, there is no audio quality or character differences between using balanced vs. unbalanced configuration assuming there are no other factors affecting the audio quality, such as a ground loop or RFI.
-Tim -----Original Message----- From: flexradio-boun...@flex-radio.biz [mailto:flexradio-boun...@flex-radio.biz] On Behalf Of y...@aol.com Sent: Monday, February 02, 2009 12:40 PM To: FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Balanced vs. unbalanced microphone inputs Have been following this line for a while, going back to the original question, about audio quality being better using a balanced mic or a std 2 wire mic. Did anybody come up with a conclusion? I always found audio quality about the same ,but the balanced always seemed to handle hum and rf problems better than a un balanced mic. curious what anybody else has found. thanks dale wt4t -----Original Message----- From: Lee Mushel <herbe...@centurytel.net> To: Lux, James P <james.p....@jpl.nasa.gov>; Dennis <radio...@charter.net>; Chris seeber <ctsee...@cox.net>; DudleyHurry <jhu...@austin.rr.com>; Ray Andrews <k9...@rnacs.com> Cc: flexradio@flex-radio.biz Sent: Mon, 2 Feb 2009 8:06 am Subject: Re: [Flexradio] Balanced vs. unbalanced microphone inputs I hesitate to comment on this topic since already today my ideas on various subjects have been strenuously rejected but to carry the discussion to the extreme of shortness I would mention that when I consider feedlines, rather than mike cable, I do use long bulkhead connectors to bring the balanced line into the shack through the house wall. Sure seems to work and I don't think the impedance bump is great enough to do any damage....Feedline to PL259s on the bulkheads then PL259 on the inside house wall to the tuner.....I guess I never even give thought to any terrible effect at audio frequencies. I would use cable rather than bell wire, but.... 73 Lee K9WRU ----- Original Message ----- From: "Lux, James P" <james.p....@jpl.nasa.gov> To: "Dennis" <radio...@charter.net>; "Chris seeber" <ctsee...@cox.net>; "DudleyHurry" <jhu...@austin.rr.com>; "Ray Andrews" <k9...@rnacs.com> Cc: <flexradio@flex-radio.biz> Sent: Monday, February 02, 2009 8:17 AM Subject: Re: [Flexradio] Balanced vs. unbalanced microphone inputs > > > > On 2/2/09 5:13 AM, "Dennis" <radio...@charter.net> wrote: > > > This is only true if the coax is properly matched, on both ends, to its > > characteristic impedance, whether you're using it single ended or > > differential.... So, using coax to replace tuned feeders is very problematic > > (looses go up) unless both ends of both coax cables are matched to their > > characteristic Z. > > Not necessarily. It depends on how long the piece of coax is, and whether > you happen to be at a voltage or current peak. It's good to remember that > those published loss numbers (whether matched, or recalculated for a > mismatch and including the circulating currents) are essentially the > "average" over a wavelength. If you're looking at substantially less than a > wavelength (and 5 ft is substantially less than a wavelength, even on 10 > meters), the loss could be higher or even lower. > > For HF, the loss is mostly the IR loss in the center conductor, and, so, i s > proportional to the current squared in that section of coax. A line with a > big mismatch will have a current that varies along the line, but which > (geometrically) averages to something in between. If you look up the > "mismatched line loss" or calculate it, you'll be getting that average. At > some places the loss will be less: potentially LESS than it would be in the > matched case, if the current is particularly low. > > > Here's a sort of special case. Consider a piece of transmission line that's > exactly a quarter wavelength long, and shorted at the far end. The SWR is > infinite. At the source end, the voltage is a maximum, but the current is > almost zero, so the losses per unit length are very small. Move out along > the line, and the voltage drops (eventually to zero) and the current > increases and the IR losses per unit length increase. > > (This is aort of special case, because there's not any power actually > flowing in the line.. BUT, imagine, instead of a short, that a quarter > wavelength of 50 ohm line is terminated in, say, 10 ohms, and it's driven by > a 250 ohm source... E/I = 250 at the source end, E/I = 10 at the destination > end) > > This kind of thing is a royal pain to calculate by hand, so resorting to > some sort of program or spreadsheet that does the transmission line > equations is definitely worthwhile. I like XLZIZL, which is an excel > spreadsheet that lets you put in up to 5 "stages" in a ladder, where each > stage is either a transmission line, some reactive components, or a > transformer. There's other programs too. I don't know if ARRL's TLW does > multiple transmission lines. > > > Jim > > > _______________________________________________ > FlexRadio Systems Mailing List > FlexRadio@flex-radio.biz > 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 FlexRadio@flex-radio.biz 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 FlexRadio@flex-radio.biz 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 FlexRadio@flex-radio.biz 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/
