[Elecraft] Question about antenna matching

CUTTER DAVID d.cutter at ntlworld.com
Wed Jul 14 04:35:23 EDT 2021


You might find some answers here:
https://www.dj0ip.de/antenna-matchboxes/
On the next page he shows all the results from published data. 

David G3UNA

> On 14 July 2021 at 07:29 Julia Tuttle <julia at juliatuttle.net> wrote:
> 
> 
> 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 <wa6vab at 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 at 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 at 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 wa6vab at gmail.com
> >
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:Elecraft at 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 julia at juliatuttle.net
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at 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 d.cutter at ntlworld.com


More information about the Elecraft mailing list