Hello, I am having a little trouble interpreting Smith Chart Impedance. If the NanoVNA header reads 52.2 +J46. Is 52.2 Ohms the total impedance or is 52.2 just the real part? Or do I use the IZI menu item to display total impedance (Real+Imag)? Thank you!

52.2 is the real part (resistance). Yes, the |Z| menu item will give
you the magnitude of the impedance.

Thank you David! That helps! I'm guessing something like a Cartesian or Polar coordinates plot would be needed to get the Magnitude from the real and imaginary parts. Is that correct?

Isn't the magnitude represented by the distance between the center and any point on the Smith Chart???

The only point on the Smith Chart which is 50 ± j0 is the center, bull's
eye. This can also be some normalized value other than 50-ohms. But it is
always real with no reactive component. Anything on that horizontal line
across the middle of the chart is real, no reactance (reactance indicated
by the ± jX term). Above that horizontal line represents some real part
(the first term) plus some inductance part (the + jX term). Below that
horizontal line represents some real part (the first term) plus some
capacitance (the - jX term). Anything above or below the central
horizontal line contains both a real and reactive component.

Dave - WØLEV

On Mon, Sep 23, 2024 at 1:31 AM Matthew Rapaport via groups.io <quineatal=
gmail.com@groups.io> wrote:

Isn't the magnitude represented by the distance between the center and any
point on the Smith Chart???

--

*Dave - WØLEV*


--
Dave - WØLEV

Yes, the R & X are cartesian coordinates. The magnitude is sqrt( R^2 +
X^2 )

If you use the box of your nanoVNA alone; that is to say not connected during the measurements to a computer, you can, on most models, save the measurements in a file resident in the box.

Once back home, in the shade, if you connect the box to a computer, you can retrieve this file and, with suitable software, quietly consult your measurements and possibly make calculations on them
--
F1AMM
François

On Sun, Sep 22, 2024 at 06:30 PM, Matthew Rapaport wrote:

Isn't the magnitude represented by the distance between the center and any
point on the Smith Chart???

The distance between the center and any point on the Smith chart is the magnitude of the reflection coefficient known as Gamma. Abbreviated as |S11| or |Γ|. The angle from the horizontal line to this line is the angle of the reflection coefficient. The maximum value of |S11| or |Γ| is 1 and the minimum is 0. If you take 20*log10 of this number you get the Return Loss and the SWR can be calculated by (1 +|Γ| )/(1 -|Γ| )

Every point on the Smith chart represents a complex (R +/-jX) impedance point which is scaled to to the system impedance. This is non-linear mapping and was created by Smith. You can also calculate the complex impedance from the complex reflection coefficient using this formula.
Z (complex) = Zo * (1 +Γ )/(1 -Γ|) where Zo is the system impedance like 50 +j0 and Γ is a complex number in the form a+/-jb.

Roger

Just to point out that what was proposed by Smith was not scaled to the system impedance. The Smith chart was centred on 1 ohm and all point had to be normalized to 1 ohm, and then un-normalized to work back to real values.

That was because everything was on paper and you did not need different charts for different system impedances.
Paper charts centred on 50 ohms came later, and computers subsequently made things much easier to cope with different system impedances.

Regards
Jeff

________________________________________
From: nanovna-users@groups.io <nanovna-users@groups.io> on behalf of Roger Need via groups.io <sailtamarack@...>
Sent: 23 September 2024 17:19
To: nanovna-users@groups.io
Subject: Re: [nanovna-users] Smith Chart Impedance

On Sun, Sep 22, 2024 at 06:30 PM, Matthew Rapaport wrote:

Isn't the magnitude represented by the distance between the center and any
point on the Smith Chart???

The distance between the center and any point on the Smith chart is the magnitude of the reflection coefficient known as Gamma. Abbreviated as |S11| or |Γ|. The angle from the horizontal line to this line is the angle of the reflection coefficient. The maximum value of |S11| or |Γ| is 1 and the minimum is 0. If you take 20*log10 of this number you get the Return Loss and the SWR can be calculated by (1 +|Γ| )/(1 -|Γ| )

Every point on the Smith chart represents a complex (R +/-jX) impedance point which is scaled to to the system impedance. This is non-linear mapping and was created by Smith. You can also calculate the complex impedance from the complex reflection coefficient using this formula.
Z (complex) = Zo * (1 +Γ )/(1 -Γ|) where Zo is the system impedance like 50 +j0 and Γ is a complex number in the form a+/-jb.

Roger

On Tue, Sep 24, 2024 at 04:41 AM, G8HUL wrote:

That was because everything was on paper and you did not need different charts
for different system impedances.

It was also convenient when manipulating transmission line components, you normalize your impedance to the transmission line impedance and the impedance transforms along circles centered on the center of the chart, so you can draw them with a compass. I got good at re-normalizing impedances because you do it a lot. It was like a gift from Heaven when COMPACT (on timeshare via a TI Silent 700 acoustic modem over a phone handset) became available in the'70s.
https://en.wikipedia.org/wiki/Compact_Software
73, Don N2VGU