That's pretty much picking nits, in my opinion. It doesn't really matter whether you physically locate needed complex reactance at the antenna or present it to the antenna via the transmission line physics of a feedline ... the net result that exists at the antenna is exactly the same (neglecting transmission line losses, of course) in either case. The only relevant distinction I can see is that "tuning" more accurately refers to bringing something to resonance rather than also transforming it to a different load impedance, but that falls into the category of useless semantics for me and I can give you all sorts of examples where it would be next to impossible to distinguish electrically where an antenna ends. The dividing line between an antenna and the rest of the system is not at all as definitive as you suggest, and pretending it is seems more likely to give a false impression of how things really work than not.
73, Dave AB7E On 9/18/2012 11:52 PM, Adrian wrote: > Matt, Of course I don't question Don's technical stature, however "tuning > the antenna" is a poor choice of explanation, and can give a false > impression to those weak on the subject. Adding 'system' would have been a > good move as you indicate. We tune where we measure. > > -----Original Message----- > From: Matt Maguire [mailto:[email protected]] > Sent: Wednesday, 19 September 2012 3:35 PM > To: vk4tux > Cc: [email protected] > Subject: Re: [Elecraft] KX3 ATU > > > On 19/09/2012, at 2:48 PM, vk4tux <[email protected]> wrote: > >> Don, When you say "The ATU will tune the antenna to an acceptable >> SWR", you are contradicting yourself, because as you rightly said the >> tuner does not change the antenna feedpoint swr. > It is clear from the context that Don meant the ATU will tune (ie. match) > the antenna *system* to the radio, where the antenna system consists of the > ATU, antenna and connecting feedline considered as a single unit. This of > course does not mean that the VSWR is 1:1 everywhere within that system. > > The theory predicts that the measures VSWR will be constant along a > *lossless* feedline. As you point out, practical feedlines do have losses. > This will include I^2.R copper losses, but there can be losses from other > sources as well, such as dielectric losses. Often such losses will be > modelled as some sort of equivalent series resistance. > > 73, Matt VK2ACL= > > ______________________________________________________________ > 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
