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Re: SMITH CHART TUTORIAL


 

Nbridgema wrote:
Reading off the chart, we see the following values:...
Would you please explain where these values are seen?
The answer is, you cannot directly read frequency off of the Smith chart.
There should be little notes and arrows added as annotation to the chart,
telling where the 14.0mhz, 14.175mhz, and 14.35mhz points of the blue arc are at.

The blue arc goes clockwise from 14.0mhz in the upper left to 14.35mhz in the lower right.
If you zoom in and put on your best reading glasses, you may see a little green pixel in the blue arc
just below the horizontal line identified as "0.2", this point on the blue arc is 14.175mhz.

The first entry of the table after the chart says that the reflection coefficient at 14mhz
is (-0.12, j0.26). That's a complex number, having a real part of -0.12 and an imaginary part of j0.26.
This corresponds to the upper left end of the blue arc.
The real part of -0.12 is slightly to the left of the center vertical axis of the chart, a bit more than halfway to that first -0.2 vertical line.
The imaginary part of j0.26 is up from the center horizontal axis of the chart, a bit above the first horizontal marker at 0.2.


There's all of four sentences in this tutorial describing the central concept of what a Smith Chart is:
Radio operators are inherently familiar with the concept of standing-wave ratio, i.e., a measure of how well a load
is matched to a transmission line. A slightly more obscure concept is that of the reflection coefficient.
Notated using the Greek letter gamma (¦£), the reflection coefficient describes how much of an
electromagnetic wave is reflected by an impedance discontinuity such as a mismatched load. ...
First, let¡¯s plot the real and imaginary components of ¦£ for this DUT on a rectilinear graph.
So I'd say Aldo's tutorial is not very useful to someone starting out, you pretty much have to already know
what a Smith Chart is. The title should give a hint of this: "Revisiting the Smith Chart".
But if you do understand the basics, there is plenty of good information there.

Here's an old post about a different Smith Chart tutorial: /g/nanovna-users/message/5223
This tutorial does try to explain in simple terms what a Smith Chart is.
That entire thread might still be of interest to those thinking about how to better document these VNA's.

Another good resource for understanding the Smith Chart is at

Jerry, KE7ER

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