When you first get started, you are going to sound nervous.  If you have never done this before, and possibly even if you have, you will have that shake and quiver in your voice that will give you away.  So, what can you do to get rid of this?  Well, I've got a simple answer that you will probably not like - start making regular episodes and power through it.

Nope, I don't know any tricks other than just doing the work. And, I cannot tell you what your magic number is.  But at some point you will hit that magic number, the nerves will subside and this will feel natural to you.