I agree except that even at 500KW a 2:1 or greater is the norm with open wire line.
Sent from my iPhone > On Apr 9, 2019, at 19:10, Fred Jensen <[email protected]> wrote: > > Well, the reflected power is created by a "virtual transmitter" at the > feedpoint of the antenna and heads down the coax which has a surge impedance > of Z0 ohms. It meets the SO-239 at the TX and sees an impedance of Z1, the > impedance presented by the PA and output filters. If Z1=Z0, the power is > dissipated as heat in the PA and associated RF circuitry. If Z1<>Z0, some is > dissipated and some is reflected, where some is radiated, and some is > reflected [virtual transmitter again]. Ad infinitum, and when forever is > over, it is all gone and everyone lives happily ever after. > > SWR and all the associated measuring equipment and concern with it only > became an issue when: 1) Coax replaced parallel lines and; 2) Resonant output > circuits were replaced by solid state amplifiers with non-resonant filters. > When I sat for the Extra in early 1956, the only question that involved > standing waves was one about how Lecher Lines could be used to measure > transmitter frequency. > > It's important today but calculating it hasn't changed. At 10 W, a 2:1 SWR > will probably work ok. At 1500 W, a solid state amplifier may not be happy > with the voltages developed at its output connector. > > 73, > Fred ["Skip"] K6DGW > Sparks NV DM09dn > Washoe County > >> On 4/9/2019 5:56 PM, Don Sanders wrote: >> Since no one has answered your question. I will venture a >> supposition that many know but few will speak out. >> And some still remember their CB days and the erroneous >> advertising saying the power is lost. >> Reflected Power flows back down the feed line and is subjected >> to the normal feed line loss. It then is "reflected" back toward the >> antenna, again subject to the feed line loss, where some of it is >> radiated and some reflected again. >> This continues until the power is dissipated. The book "Reflections" >> has a very good but somewhat technical explanation. >> Therein also is the reference to forgetting about striving for the >> "Holy Grail" of 1:1 SWR. >> And concentrating on getting it low enough that the transmitter will >> supply full power output. Also using the best low loss feed line and >> proper matching when possible of the feed line to the antenna. >> >> Dr. Don W4BWS >> > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
