If you can get it to accept power then the power either radiates or goes to heat. In the old days of vacuum tubes arcing, sparking and how red the plates are getting was part of the tune up process! A high SWR on a low loss transmission line is not a problem by itself. John Ferrell W8CCW "All that is necessary for the triumph of evil is for good men to do nothing." -- Edmund Burke http://DixieNC.US ----- Original Message ----- From: "Vasile Surducan" To: "Microcontroller discussion list - Public." Sent: Saturday, October 25, 2008 1:09 AM Subject: Re: [EE] SWR > How the hell an antenna may work fine with a 3:1 SWR ? > :) > > On 10/24/08, Nate Duehr wrote: >> Sean Breheny wrote: >> > Hi Nate, >> > >> > I think I get what you are saying, but reducing power will not change >> > the SWR (since it is a ratio). I think in reality that there is some >> > threshold for reflected power that the transmitter has and above that >> > level it will cut down on the output power to get the reflected power >> > below that level. >> > >> > One thing which that article seems (in a quick skim) to fail to >> > address is that reflected power can damage a transmitter. This >> > aggressive power reduction MAY be necessary to protect the transmitter >> > output stage. It isn't intended to protect the stuff outside of the >> > transmitter (antenna, feedline, etc.) and so it would not be "better" >> > if the transmitter did not cut back. That being said, it could be that >> > some transmitters are too aggressive in doing so. >> > >> > Sean >> >> He does mention it as the reason the transmitters have that behavior, >> and that ALL modern transistor-final PA transmitters are very aggressive >> at protecting themselves. >> >> Often an antenna system that worked "just fine" at a 3:1 SWR on an old >> tube rig will fold-back power on a modern rig to the point where the guy >> on the other end can no longer copy you. >> >> The fold-back circuit can cause a much higher power "loss" overall in >> your transmitted signal than having a non-resonant antenna system. Many >> newer hams do not understand this. >> >> His point in the article, is that you can do the math (something >> Amateurs do less and less these days... "plug and play" radio operation, >> so to speak) and prove your overall system's performance. And the >> numbers might surprise you if you take the rig's protection circuitry >> into account. (Something that people also rarely do.) >> >> And then if you're like me, you go MEASURE it to see if it matches >> theory, or find the reason why not. And personally, I prefer resonant >> antennas, but if I have to work a band that just won't work with my >> antennas, I use a tuner and "make the radio happy". >> >> Nate >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist