Smith Chart - Radially Scaled Parameters

I need to understand how to use these two Smith Chart Scales: 1) S.W. LOSS COEFF and 2) S.W. PEAK (CONST. P).

Could someone help me?

Do you have any example of use?

Thanks in advance.

Check these, one of the best smith chart series

https://www.youtube.com/watch?v=tbSr...4292FBEAB55A1C

https://www.youtube.com/watch?v=6QSn...444183F9F7596C

Dear Ata_sa16,

Thank you for your answer, but I have not found the answers to my questions in these videos. However, these videos are very good to start learning. This is not my case.

Best regards, Carlos

VSWR is a fairly old concept, that might have meant a lot in the 1950's, but mostly we use either return loss or voltage reflection coefficient nowadays. I think it was only popular since an SWR meter was easy to make with a detector diode and a way to slide it along a 50 ohm transmission line. This was decades before HP came out with a network analyzer!

p = voltage reflection coefficient = (S-1)/(S+1)

So if you have a VSWR of 2.2:1, the reflection coefficient is (2.2 - 1)/(2.2 + 1) = 0.375 magnitude

So if you want to know the SW Loss Coefficient...you use p instead.
In a LOSSLESS network, Power incident = Power reflected + Power transmitted.

Reflection coefficient is a voltage parameter, so to turn it into something like a power parameter you square it.

So Power Incident = 1 = p2 + t2
where p2 is proportional to the power reflected, and t2 is proportional to the power transmitted.

So if you want to know the transmitted voltage wave amplitude....t =√ (1 - p2) = √ (1 - 0.3752) = √0.859 = 0.927

the transmitted voltage wave amplitude is 0.927 times the incident.
The insertion loss is 20 Log .927 = 0.6582 dB

you could use a page like this too:
https://www.pasternack.com/t-calcula...AaAusaEALw_wcB

A good engineer should have these basic formulas in you head, and be able to do the calculations as a check on their fancy new computer simulation programs. (my opinion)

Dear biff44,

Thank you for your answer.

I know these concepts that you are trying to explain me, but this is not the matter.

I am trying to get information about the these old radially scaled parameters, because I want to understand how these old engineers used them.

Anyway, thanks for your answer.

Best regards, Carlos

What do you want to know ?

Prepare a set-squares and compasses.
There is no need to use complex calculator.

Their phisical meaning, how to use them and some examples.

biff4 showed them and you answered you know them.
https://www.edaboard.com/showthread.php?t=369815#4
Again, what do you want to know ?

https://www.edaboard.com/attachment....5&d=1501390134
https://www.edaboard.com/attachment....6&d=1501390380

Reconsider what you want to know.

Surely study my answer in https://www.edaboard.com/showthread.php?t=369815#6

Thank you biff4, I will wait for other reasonings that include exactly the scales that I am looking at. The lower ones. Thank you again.

What do you want to mean ?

I want to understand the phisical meaning of these two scales 1) S.W. LOSS COEFF and 2) S.W. PEAK (CONST. P) exactly. What is the relation with the standing wave?

(Pincident+Preflect)/(Pincident-Preflect)=(1+|S|^2)/(1-|S|^2)
This is also called as "Transmission Loss Coefficient.

sqrt( (1+|S|)/(1-|S|) )=sqrt(VSWR)=|V|max/|V|max,0
where "|V|max,0" mean maximum voltage when S is zero at load.

Thank you pancho_hideboo for the answer! :)

Could you show an example where exactly these two rules are used? I mean, are these two scales really necessary? What type of problems would be solved by exactly these two scales?

Thank you very much.

I showed you physical definitions of them clearly.

Guessing from your response's level of this thread, I don't think you can understand them even if I provide simple examples.
Consider and study by yourself.

I don't think these have much value.

(1) is for correction factor that is used to evaluate the attenuation caused by mismatched impedance in a lossy line.

(2) is for confirmation of possibility of high voltage.

To my surprise, guage is wrong in almost all Smith Charts which are available on Net.
https://www.microwaves101.com/downloads/smith.PDF

This is a clear evidence that these guages are not used and valuable.

Guage has to be corrected like attached figure.

It seems that no one had paid attention to these scales before XD. Thank you pancho_hideboo.

Attached guages are orginals by P.H. Smith.

P.H. Smith:"Transmission Line Calculator", Electronics, pp.29-31, Jan. 1939.

P.H. Smith:"An Improved Transmission Line Calculator", Electronics, pp.130-133, Jan. 1944.

Scales are like following in "1944.png".

MIN. LIMITS = |V|min/|V|min,0 = 1/sqrt(VSWR)
MAX. LIMITS = |V|max/|V|max,0 = sqrt(VSWR)

DB RATIO = dB20(VSWR)
MAX./MIN. RATIO = VSWR

DISSIPATION 1DB. STEPS ; ATTENUATION
DISSIPATION SW. LOSS COEF. = (Pincident+Preflect)/(Pincident-Preflect)=(1+|S|^2)/(1-|S|^2)

REFLECTION LOSS(DB) = -dB10(1-|S|^2)
REFLECTION COEF. = |S|

I have found the 1944 article and it is very interesting, but I have not found the "reflection coefficient magnitude (voltage) inside it... :( Can someone send me this paragraph if you have it?



Besides, the scale S.W. Peak Coeff (Const. P) does not appear in these articles. Can you provide me an article where this scale is show?

What do you want to mean ?
Definition of reflection coefficient is obvious.

It is "MAX. LIMITS" in original guage.

Yes Pancho I think it is obvious but I believe that this page had dissapeared from the original article. It does not matter.

Ok the other hand, I am going to think about this Max limits in depth and if I have some doubts I Will get back yo you.

Thank you very much for your help.

Anyway, do you recommend me antoja extra article to read?

Thanks again.