By "Holy Grail" I mean a
* notune,
* allHFband, and
* fulllegalpower (incl. negligibleloss)
antennafeedline system. W1HIS.
Dennis, K7FL, wrote:
>>[Chuck, W1HIS] was able to find one _fixed_ setting of the tuner
>>for which the SWR on the coax (and therefore the loss) was
>>tolerably low across _all_ HF bands 80 through 10 meters....
>
>
>Chuck,
>
>This is a highly intriguing idea, so simple in concept (albeit
>difficult in execution) that I'm surprised it isn't referenced in
>more literature. I have a situation that just begs for this.
>[Description snipped.]
>
>All these seem like a lot of variables. I was going to look for the
>magic horizontal lengths in EZNEC to balance pattern with
>impedance.... But as I said, this looks like a host of variables to
>juggle  could there indeed be a methodical approach to this
>problem???
>
>Thanks Chuck  very interesting thread
>
>Dennis, K7FL
See the response to Howard K2HK that I posted a halfhour ago. I
suggested using Microsoft Excel for the simultaneous multivariable
optimization, because (1) Excel has such an optimization capability;
(2) probably most hams have Excel; and (3) Excel does complex
arithmetic, so formulas representing transmission lines, simple
lumpedelement networks, and series and parallelconnected
impedances and admittances are easy to code. I've written Excel
macros even for _lossy_ transmission lines  complex hyperbolic
functions and all.
I don't know how to model an antenna accurately in Excel. That's one
reason why I wrote that I needed accurate antenna feedpoint impedance
_measurements_. Another reason is that, even with the best available
antenna modeling programs (I use NEC4) it's difficult to calculate
feedpoint impedance very accurately. With care you can come close,
but probably not close enough reliably to design a matching system
"openloop."
Thus, in my view, the chief unsolved problem is that of accurate
antenna feedpoint impedance measurement.
73 Chuck.
