why 50 ohms impedance?

hi,

can anybody explain me why 50 ohm impedance? I know it is for impedance matching and provides maximum power transfer.

Is there a better way to explain why only 50 ohms? scientific formula or explanation?

Thanks

It is not only 50Ω, it is just most common impedance used. 75Ω is used in broadcasting more often for example.

I've seen various web sites discussing that question. Here's one:
http://www.microwaves101.com/encyclopedia/why50ohms.cfm

Because of the log nature of the impedance with physical dimensions, it is difficult to make transmission lines of less than 30 or more than 90 ohms impedance.

hi echo47,

i got the answer. this is a great explanation.

Thanks

refer
https://www.edaboard.com/viewtopic.php?p=903307#903307