The bridge of Wheatstone, or equivalent.
I always determine Zin too in the simulator Electronic Workbench, before I
go to build
it in real.
But you can do it directly in real.
Connect a variable resistor between output generator and input 2N3866.
Add an 2 Chan. Scope, output generator to Chan 1, input 2N3866 to Chan 2.
A broadband Oscilloscope is not needed, it is the amplitude that is going to
be
measured.
Turn the potentiometer until you have half the amplitude of Chan 1, on Chan
2.
Now the variable resistor equals Zin.
Power off, losen variable resistor, and measure it with your Ohm meter.
It tells you the impedance @ generator frequency.
1 Chan. Scope can do the job, you keep the amplitude of the generator in
mind,
turn the potentiometer until you have half the amplitude at input 2N3866.
Use 10 :1 probes, good luck !
Source of information about RF test methods, the book Test equipment for the
radio amateur RSGB author Clive Smith, not the one of the Smith Diagram, hi
!
On the internet, Google finds everything, you have to sort out things, and
specify
well.
One serious source is the Agilent homepage. (Hewlett Packard)
The idea how to measure Zin comes from a course Electronics by Dirksen in
Dutch.
"RF measurements, the best keeped secrets of Electronics" statement by me.
Greetings... Bas Viel.



"David" schreef in bericht
...
Hi,

Does anyone here know how I can determine Zin of 2N3866 at 150MHz, Output
is
matched to 140R for 200mW.

I have an RF sig gen, Spectrum analyzer, RF power meter, 300MHz scope and
VSWR brdige with built-in detector.

Also, anyone know of a good site that explains RF test methods. (Measuring
filter response etc)

Thanks

Regards
David