Hello Cecil,

On 2 mayo, 14:37, Cecil Moore wrote:
On May 2, 5:33*am, Wimpie wrote:

Are you familiar with the concept of S-parameters where you determine
impedance by measuring of reflection coefficient?

Exactly how do you determine the s-parameters for a single-port black
box? It is my understanding that an s-parameter analysis requires an
input port and an output port to be able to measure the parameters.
Where is the input port on an RF source?

I used a 2 port VNA frequently for antenna measurements, with the
difference that a single port calibration takes less time than a full
two port calibration.


What you seem to be measuring is the effect of one or more physical
impedance discontinuities existing in an environment of interference.
Is what you are measuring the actual dynamic source impedance? If I
understand correctly what Walter Maxwell is saying is that whatever
combinations of physical impedance discontinuities from which you guys
are reflecting your test signals, it/they are *not the source
impedance* which is a V/I ratio that originates in the source. A V/I
ratio and a physical impedance discontinuity do not yield the same
reflection coefficients for a 2-port device.
--
73, Cecil, w5dxp.com
"Halitosis is better than no breath at all.", Don, KE6AJH/SK

I would recommend you to measure something yourselves, or put it into
a simulation. You will see that it doesn't matter whether you use a
deltaV/deltaI setup (complex values, not magnitudes) or reflection
(time varying phase of VSWR) measurement. Just try to explore other
paths and discover other insights.

It doesn't matter when you are measuring a single port device that
contains a generator in it (as long as your VNA setup is able to
distinguish between the output generated by the single port device and
the reflection towards the VNA).

There is similarity with measuring antenna impedance (single port
measurement) when close to (broadcast) stations. Your antenna is a
generator in that case. You can't use the non-coherent type of VSWR
analyzers as the detector detects the signal from the broadcast
station also. However when using a device with a coherent
(multiplying) detector you can, as the detector doesn't respond to the
output because of the (broadcast) station.

With Tom's HP89410 setup, the injected signal for S11 can be well
within the modulation bandwidth of SSB (that means well within 1 kHz
of the transmitter's carrier frequency).

When you have good understanding of diode detectors, you can even do
it without a VNA by using heterodyning and put your focus on the phase
and amplitude of the beat frequency.

With kind regards,


Wim
PA3DJS
www.tetech.nl
without abc, PM will reach me very likely