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Calculating L and C values for Matching PI filter using NanoVNA


dave 2022/01/02 13:07

Firstly - Fantastic Piece of Kit - thank you to the community that brough us the NanoVNA!

So I am using this to characterise an PCB based antenna. Using the NanoVNA I have taking the following measurements (see screen shots).

I want to build a PI matching filter to match this antenna to an F=868mHz, impedance of 50R..  The Nano for this Freq is giving me an impedance of Z=13.47-j39

All of the tutorials that do this, using a smith chart read the values from the smith chart and use that to plot the Zo to correct it, and then use this calculate the L and C values, but I don't see a way of doing this with the NanoVNA.

How do I do this with a NanoVNA plus?  Whats the math I need to apply or can the Nano do this for me?

thanks

Dave

Wojtek SP9WPN 2022/01/03 01:26

No, Nano won't do the math. I'd recommend you to have a look at SimSmith software, great learning tool to understand Smith charts and impedance matching.

W1RS 2022/01/03 04:35

Another good one that is free for up to 5 elements.
http://www.fritz.dellsperger.net/smith.html

schweppe 2022/01/03 14:33

Hello Dave,

I use the progam "smith" from J.Dellsperger to solve such problems. Look
at the picture.

73, Guenter, DK5DN

Am 02.01.2022 um 22:07 schrieb dave@conficioltd.com:

W0LEV 2022/01/03 17:11

SimSmith includes various matching topologies built into the various
applications within the program. It will do the math for you. Download
and install SimSmith from the following URL:

http://www.ae6ty.com/smith_charts.html

An excellent tutorial has been written by WØQE and can be accessed at:

https://www.w0qe.com/SimSmith.html

Dave - WØLEV

On Mon, Jan 3, 2022 at 4:29 AM <dave@conficioltd.com> wrote:

> Firstly - Fantastic Piece of Kit - thank you to the community that brough
> us the NanoVNA!
>
> So I am using this to characterise an PCB based antenna. Using the NanoVNA
> I have taking the following measurements (see screen shots).
>
> I want to build a PI matching filter to match this antenna to an F=868mHz,
> impedance of 50R.. The Nano for this Freq is giving me an impedance of
> Z=13.47-j39
>
> All of the tutorials that do this, using a smith chart read the values
> from the smith chart and use that to plot the Zo to correct it, and then
> use this calculate the L and C values, but I don't see a way of doing this
> with the NanoVNA.
>
> How do I do this with a NanoVNA plus? Whats the math I need to apply or
> can the Nano do this for me?
>
> thanks
>
> Dave
>
>
>

--
*Dave - WØLEV*
*Just Let Darwin Work*

DiSlord 2022/01/03 10:08

On Mon, Jan 3, 2022 at 01:26 AM, Wojtek SP9WPN wrote:

>
> No, Nano won't do the math. I'd recommend you to have a look at SimSmith
> software, great learning tool to understand Smith charts and impedance
> matching.

In my fw for nano exist Measure->L/C MATH (on old fw in Marker->Measure->L/C MATH)
in this mode Nano calculate up to 4 solution how made 50 Om from measured data at current marker frequency

Karl Jan Skontorp 2022/01/03 12:20

Pasan is an nice start to learn about matching with smith chart. It's easy to learn and how to use...
Free downlaod here:
http://www.science4all.nl/?Electronics___Pasan

Karl

PS. As DiSlord says, matching calculations are built into his firmware...

dave 2022/01/03 15:04

Thanks Schweppe ..  thats looks really interesting, I'll have a look at this now..

dave 2022/01/03 15:15

On Mon, Jan 3, 2022 at 09:26 AM, Wojtek SP9WPN wrote:

>
> SimSmith software

Thanks Wojtek - just working my way through this

dave 2022/01/03 15:15

Thanks for replay Dave - taking a look now and getting my brain warmed up!

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