Load pull testing transceiver LNA input, impedance tuner DIY alternative

[tretmax]

Hey all,

Transceiver vendors not always provide best components for input impedance matching in all variety of frequencies range that transceiver itself support, often provide impedance matching network components only for single range of frequencies and some instruction how to get best matching for custom frequencies. And this method involve pretty complex & expensive devices, and if some devices became more affordable with time(VNA) some rare devices so far hard to find for reasonable price.

Any homemade alternative could be done for variable impedance tuner in range from 400 MHz-1 GHz ? I am generally get idea how variable impedance tuners works, but some details not clear and this not fully allowed me to think about alternatives that could be fit here, if get few used coaxial adjustable stub(tuning line) connect it with each other, could this cover varies of impedances ?

 

[BigBoss]

For Optimum Input Impedances are given for Lowest Noise Figure of the Transceiver.
Even you design and build a Sliding Tuner you cannot be sure that the Tuner works well or not because you don't have a Reference or in other-word Calibration Sources.
You can not verify this Tuner will give you the Impedance that you read.
Sliding Tuners or Load-Pull or Source Pull Tuners are seriously manufactured by 2 companies only in the world. Focus Microwave and Maury Microwaves.
Imagine how this business is hard and needs lot of experiences.

 

[aliarifat794]

Coaxial stub tuners can be a practical solution for homemade impedance tuning. These tuners use sections of transmission line (coaxial cable) as reactive elements (inductors and capacitors). By adjusting the length and position of these stubs, you can achieve the desired impedance transformation.

 

[dick_freebird]

I've seen load pull bench setups which looked "almost
homemade" (manual crank inductor etc.). But these do
not give you a nice front panel L value you can believe
in - more like, twiddle to the magic point and then measure
"what you did" on the jig minus the DUT.

These evidently were so painful that cheapskate management
actually spent money on pro gear.

 

[tretmax]

For Optimum Input Impedances are given for Lowest Noise Figure of the Transceiver.
Even you design and build a Sliding Tuner you cannot be sure that the Tuner works well or not because you don't have a Reference or in other-word Calibration Sources.
You can not verify this Tuner will give you the Impedance that you read.
Sliding Tuners or Load-Pull or Source Pull Tuners are seriously manufactured by 2 companies only in the world. Focus Microwave and Maury Microwaves.
Imagine how this business is hard and needs lot of experiences.

Thank you, make sense.
I am checking this from another point and i am not really sure if i need to know exact impedance from variable impedance tuner itself, i see test process like this:
you connect transceiver#1 input to another transceiver#2 output via some loss line(attenuator) and between them place impedance tuner, on transceiver#1 you have demodulated signal data from transceiver#2 and adjusting attenuator & impedance tuner you try to find point where signal on minimum level could be still demodulated with certain amounts of errors(BER) and once you find that you just plug VNA to impedance line and check impedance value from VNA itself, so basically i need something that could vary impedances without showing what this impedance is -- this i always could measure from VNA connected to tuner.

 

[vfone]

This slide screw tuner will do the job:

https://focus-microwaves.com/wp-content/uploads/2022/10/DS-MMT304-V01.pdf

..and how to use it for noise figure (BER) measurements:

https://focus-microwaves.com/wp-content/uploads/2019/05/AN-42-Using-Stub-Tuners-and-Slide-Screw-Tuners.pdf