# Homework Help: Coaxial Speed of Propagation

1. Jul 11, 2009

### CNX

I know my impedance minima and their associated frequencies for a particular coaxial cable. How would I go about deriving an equation that will let me calculate the speed of propagation and the dielectric constant?

My only hint is to consider the case for which Z = 0 but I don't know where to start.

I only have Feynman section 24-1 as a reference and he doesn't seem to cover this.

2. Jul 13, 2009

### turin

I need more information to help you. For example, I assume that you are considering TEM? The characteristic impedance ]i[vanishes[/i]?! I didn't know that Feynman wrote a book on transmission lines - what's the name of this book?

3. Jul 14, 2009

### maverick280857

He's referring to Feynman's Lectures on Physics.

CNX: Refer to any engineering textbook on Electromagnetic Theory, specifically the chapter on Transmission Lines. For instance, you can read Cheng's book. All the equations you're looking for, are there.

Can you tell me what you mean by impedance minima...impedance as seen into the line at a point from the load is a function of the characteristic impedance, the load impedance, the operating frequency and the position coordinate (or length). Minima wrt what?