That doesn't actually answer the question "what are manufacturers measuring when they quote 10:1 matching ability?", and makes a gross and insulting generalization about the quality of equipment produced for the amateur radio market.
On Wed, Jul 14, 2021, 01:45 Ray <wa6...@gmail.com> wrote: > The Statement "This tuner will tune an 8:1 mismatch." > Is made in an Armature world, buy an Amateur person, > Not for a Professional Product by Calibrated Test Equipment. > This is Not New, it has happened for Decades. Buyer Beware. > WA6VAB Ray K3 > > > From: Al Lorona > Sent: Tuesday, July 13, 2021 9:32 AM > To: elecraft@mailman.qth.net > Subject: Re: [Elecraft] Question about antenna matching > > Thanks to Al N1AL, Jack W6FB, and Dave AB7E for great information that > helped me a lot. > > I'm in the circuit simulation business, after all, and I confess that I > was just being lazy, so I ran some simulations that confirmed what Dave, in > particular, had said. > > As suggested by Dave, I chose typical Q values of 100 for the inductor and > 1000 for the capacitor. Then I simulated as many points as I could on the > entire Smith Chart to see 1/ if the tuner could tune each point to 50 ohms, > and 2/ what the power loss was in the tuner at each of those points. Then, > I discovered that K6JCA had already done this on his excellent blog at: > https://k6jca.blogspot.com/2015/03/notes-on-antenna-tuners-l-network-and.html > . The > guy is totally professional and exhaustive in his discussions. I really > admire his work. > > Anyway, it turns out you can make a graph of power lost in the tuner > versus phase angle of the load. As you might suspect, 'easy' loads of 5 or > 500 ohms resistive (SWR = 10:1) don't tax a tuner as much as reactive loads > do. In fact, they're near (but interestingly, not at) the areas of > *minimum* power loss. > > Whenever an antenna tuner is reviewed in QST, resistive mismatched loads > are usually used. I'd like to see tuners tested with reactive loads, but > the number of loads required to do this from 160 to 10 meters would be > enormous. I see why resistive loads are preferred, because you can re-use > the loads on every band. > > I'm frustrated by imprecise statements like, "This tuner will tune an 8:1 > mismatch." What does that mean? There has to be a better way for > manufacturers to spec the exact impedance ranges that their tuners will > tune. I like the method that I used, which shades a Smith Chart in color > based on the two criteria I listed above. One picture would tell you all > about a tuner's effectiveness. No real tuner can tune the entire Smith > Chart, but the more of the chart that is covered, the better the tuner. And > if you can shade the areas of higher tuner loss in red, then that would > also tell you an important piece of information. (However, to generate such > a plot through measurement you'd probably need a very expensive load-pull > setup, which is a totally separate discussion.) > > For the L-network I simulated, a particularly difficult 10:1 load was near > the 7 - j30 ohm point, which is toward the bottom edge of the Smith Chart > at a phase angle of 282 degrees (or -77 degrees), and a similar point near > the top edge. The lower impedances with capacitive reactance were > definitely the most difficult (using power loss as the measure of > 'difficulty') for the tuner to handle, which Dave stated in his post, while > the high impedances with inductive reactance were generally more difficult. > If your antenna must be mismatched, and you're using an L-network tuner, > you want it to be > 50 ohms with a little bit of capacitive reactance, or > below 50 and inductive. > > By the way, K6JCA actually put the Elecraft KAT500 through this simulated > evaluation and it tested so well that he ended up buying one. > > > Al W6LX/4 > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to wa6...@gmail.com > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to ju...@juliatuttle.net ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
