Walt Maxwell, as far as I know, is very much alive.? He maintains the w2du.com website where Reflections-II is freely available.? Send him an email....he'll correspond with you.? He's a magnificent gentleman.
Walt does a beautiful analysis of transmission line behavior in Reflections-II.? Dust off you trigonometry book.? Long and short:? high SWR heats up coax - more so with high loss?(cheap)?coax and/or increasing frequency.? Much less of a problem with ladder line on HF, which becomes unsuitable above 50MHz. As for amplifier finals, the high SWR does not result in reflected power burning up the finals.? It is the MISMATCH between the?output?circuit of the transmitter (nominally 50 ohms)?and the load reflected?from the antenna to the transmission line input that bedevils the finals.? Here is an explanation of what this mismatch causes: http://www.mpdigest.com/issue/Articles/2009/aug/ar/Default.asp Hope that helps. 73 WA5KRP Texas -----Original Message----- From: Ray J <r...@w9ray.org> To: FlexRadio@flex-radio.biz Sent: Sun, Sep 13, 2009 12:14 pm Subject: Re: [Flexradio] flex 5000a atu, swr, and astounding arrl article Last I thought.. impedance mismatch is one if the causes of "SWR".. so, it is one in the same basically.. the transmitter expects a 50 ohm load. if the load is not 50 ohms, the rf is reflected back into the transmitter.. excessive amounts of reflected power lead to breakdown of the transistor junctions..? ? the max swr limit is what is protecting the tuner and amplifier in the radio from destruction.. the radio should have a protection circuit built in... power output should fold back as the reflected power level increases.. protecting the pa from a "damaging" amount of reflected energy.. but continuously running the radio in this manor will probably wreck it.. ? w9Ray? ? Jim Madden wrote:? > He states that impedance mismatch, not SWR, is the cause of transmitter? > failure. Given this statement, what protection exists in the flex 5000 to? > protect the transmitter from failure? Is it irrelevant what swr I operate at? > and thus I can go ahead and bump up the max SWR limit for tuning so I can? > transmit on 80m? Is there failsafe protection built-in to the flex so that I? > can't do something stupid and destroy the transmitter?? >? > >? > Jim? >? > WD7W? >? > _______________________________________________? > FlexRadio Systems Mailing List? > flexra...@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/? > Message delivered to r...@w9ray.org? > ------------------------------------------------------------------------? >? >? > No virus found in this incoming message.? > Checked by AVG - www.avg.com > Version: 8.5.412 / Virus Database: > 270.13.93/2365 - Release Date: 09/12/09 06:37:00? >? > _______________________________________________? FlexRadio Systems Mailing List? flexra...@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/? Message delivered to wa5...@aol.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/ Message delivered to arch...@mail-archive.com
