Hi !
I've read on google webs about voltage through transmission line voltage which at every point on the line we get V=(V+) + (V-)
I totally understand that equation, but it's confusing me , since we need to measure the voltage on the line at specific point, does the measure's instrument that I use, it calculates first the V+ separately , and then V- , then doing the sum between and gimme the result at specific point? or the device isn't working according to the math equation, works different but we get the same results.

How can I imagine a voltage passing through the line? I find it hard to imagine two signals simultaneously at the same point

thanks alot

 

What kind of transmission line? We need some context, so we can understand your question.

 

like this circuit here(general one not coaxial):
https://en.wikipedia.org/wiki/Transmission_line#/media/File:SmithChartLineLength.svg

How can I model that circuit in transmission line as electrical world circuit to be more clear for me what's going on?

I mean, can I for example instead of transmission line model it as "resistor with changing voltage/current over it" ?!

 

when I want to calculate the current at the middle of the line, what does it mean? isn't it the same current at the end of the line(as resistor analogy) ? because the middle of the line is series with the other middle of the line(the left of the whole line) ..so according to ohm, the same current must be passed ..

 

On a transmission line, The whole line becomes a component. You can sorta think of it as a transformer.

Only it doesn't transform voltage, it transforms impedance.

There are many models for transmission lines. Depending on what you're doing.

So, to analyze one, you need the source impedance, and the load impedance, and the impedance and length of line.

It's an AC device. Usually the SWR is measured. Standing wave ratio.

It's a ratio of the power put down the line and the power reflected back up.

As for the voltage any where on the line.....it's(hopefully) a balanced AC line.

Are you asking, or are you being asked, to plot voltage along the line?

Transmission lines can become very "weedy".

 

You can look at a transmission line like a lot of series inductors and parallel capacitors. The current or voltage that enters the transmission line and in some finite time propagates to the other end, so the instanteneous voltage and current in each section of the transmission line varies with time as the pulse travels through it.