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Hi All.

I need to build a Pi Network for my circuit as shown in the fig below.

1741926237187.png

So I have a 'Pi Matching Network' in my circuit. The datasheet asked me to build a Pi Matching Network. ( You know, how there is a series component, a source shunt component and a Load shunt component. )

Anyway, my VNA keeps telling me this: The measured load impedance is 31.9-58.5j.

The VNA is automatically generating these four groups below ( group 1 thru 4 ) of available matching parameters on the screen:

1. 5.24pF capacitor for source shunt and 28.8nH inductor in series.
Does that mean, this group does not need a Load Shunt at all? Does this mean that the proper tuning has been achieved with just a capacitor for source shunt and an inductor in series?

2. 23.1nH inductor for source shunt and 12nH inductor in series.
Does that mean, this group does not need a Load Shunt at all? Does this mean that the proper tuning has been achieved with just a inductor for source shunt and an inductor in series?

3. 97.5nH inductor for load shunt and 23.3nH inductor in series.
Does that mean, this group does not need a Source Shunt at all? Does this mean that the proper tuning has been achieved with just a inductor for load shunt and an inductor in series?

4. 15.3nH inductor for load shunt and 5.21pF capacitor in series.
Does that mean, this group does not need a Source Shunt at all? Does this mean that the proper tuning has been achieved with just a inductor for load shunt and a capacitor in series?

If the answer is yes to all the 4 above questions, then I still cant believe that a 'Pi matching Network' can exist with 1 of the 3 components totally missing.

Ty for your reply!

All four are all 2 element ell networks. If the values have been
calculated correctly each one would provide the required match. (1) has
low-pass characteristics. (4) is a high-pass network. The other two
probably have less frequency selectivity. A Pi matching network could
also do the job. The typical shunt C, series L, shunt C, is a stronger
low-pass filter, so it will attenuate harmonics better. If an element
in a Pi filter is removed, giving it an ell topology, it will not
provide the same match or filtering characteristic. The values of the
remaining two components would both need to be recalculated. There are
theoretically an infinite number of networks that can provide a given
impedance transformation. They will all have different frequency
responses. Even if you stick with a shunt C, series L, shunt C Pi
network, there are many possible sets of component values that will
provide the same impedance transformation, but with different
(transmission) frequency responses. Usually a network Q value is first
chosen.

Dave

I'm missing a lot of information to understand (in French) your participation. I remember the last line:

If the answer is yes to all the 4 above questions, then I still cant believe that a 'Pi matching
Network' can exist with 1 of the 3 components totally missing.

A 3-piece Pi adapter can be upgraded to a 2-piece L adapter.

If impedance matching is the only issue to be addressed, an L adapter will have greater bandwidth than a Pi adapter and lower losses. A Pi adapter artificially increases overvoltages and overcurrents, thus reducing bandwidth.

The measured load impedance is 31.9-58.5j.

OK, but we would need the frequency to show you the possibilities in concrete terms.
--
F1AMM
Fran?ois

-----Message d'origine-----

De la part de shlomo537678
Envoyé : vendredi 14 mars 2025 06:17

L-network values with the nano and then with the AT-100M Pro automatic
antenna tuner:

I measured one dipole antenna of mine (antenna fed with 1:1 balun, and
72-ohm Belden 8222 twin lead) with a nanoVNA and asked for a matching
network. It gave me values for C and L.
I then used this antenna tuner:

(AT-100M Pro)
That antenna tuner tells you the values it is using to match the antenna.
The values given by the tuner were approximately the same as what the
nanoVNA told me.
So then i made a simple L-network tuner on a piece of wood. Variable
capacitor (air-spaced blades) and a 4-inch-diameter coil made of 1/4"
copper tubing. I was happy with the result. Am using it on 30 meters at the
moment.

FYI the other Ali Express small tuners that have the word '100' in them,
like ATU-100, have gotten really bad reviews. I have two of these 'AT-100M
Pro' and am happy with them. Good for portable use, rechargeable battery
inside.

WN1Z
Orrin

On Thu, Mar 13, 2025 at 11:20 PM, David McQuate wrote:

Usually a network Q value is first chosen.

You can actually calculate the values of an L-Network's two components without knowing Q. It is sufficient to know just the value of the load impedance and the impedance you want to transform that load to, e.g. 50 ohms.

You can find the equations to calculate the component values for transforming a complex impedance to 50 ohms here:


And this blogpost contains a more general form of the above equations, allowing you to transform a complex impedance to any other complex impedance, not just to 50 ohms:


The equations are complicated, but you can download an EXCEL spreadsheet to calculate them here:


Best,

Jeff, k6jca

SUGGESTION: Forget about these "canned" solutions. Download and install
SIMSMITH.



There is also a accompanying tutorial at:



Dave - W?LEV

On Fri, Mar 14, 2025 at 5:51?AM shlomo537678 via groups.io <shlomo537678=
[email protected]> wrote:

Hi All.

I need to build a Pi Network for my circuit as shown in the fig below.

1741926237187.png

So I have a 'Pi Matching Network' in my circuit. The datasheet asked me to
build a Pi Matching Network. ( You know, how there is a series component, a
source shunt component and a Load shunt component. )

Anyway, my VNA keeps telling me this: The measured load impedance is
31.9-58.5j.

The VNA is automatically generating these four groups below ( group 1 thru
4 ) of available matching parameters on the screen:

1. 5.24pF capacitor for source shunt and 28.8nH inductor in series.
Does that mean, this group does not need a Load Shunt at all? Does this
mean that the proper tuning has been achieved with just a capacitor for
source shunt and an inductor in series?

2. 23.1nH inductor for source shunt and 12nH inductor in series.
Does that mean, this group does not need a Load Shunt at all? Does this
mean that the proper tuning has been achieved with just a inductor for
source shunt and an inductor in series?

3. 97.5nH inductor for load shunt and 23.3nH inductor in series.
Does that mean, this group does not need a Source Shunt at all? Does this
mean that the proper tuning has been achieved with just a inductor for load
shunt and an inductor in series?

4. 15.3nH inductor for load shunt and 5.21pF capacitor in series.
Does that mean, this group does not need a Source Shunt at all? Does this
mean that the proper tuning has been achieved with just a inductor for load
shunt and a capacitor in series?

If the answer is yes to all the 4 above questions, then I still cant
believe that a 'Pi matching Network' can exist with 1 of the 3 components
totally missing.

Ty for your reply!

--

*Dave - W?LEV*


--
Dave - W?LEV