[BC] Wave lengths

[JYRussell@academicplanet.com]

This whole thread has been Awesome.

I'm reading, and re-reading it, and looking at the diagram in the last 
glossy radio magazine (engineering extra?) that came out a few weeks ago. 
The shorts and opens part, depending on which multiple of a quarter wave 
you're looking at.  (I'm trying to imagine what you'd see with which tool as 
you looked at the cross section of the tx line when it's running.  I guess 
it would be the same as it is at the tx end, if everything's right but also 
wonder what that is... I only know how to use a SA to look at the noise 
floor for satellite stuff, so I don't know what a transmission picture looks 
like as you move along the line.)
OK, so I have to re-invent the wheel to appreciate it.
I hope you don't mind... it's just the way I seem to learn.


  I'm also reunderstanding how the size of the coax is at least partly 
dependant on the amplitude of the wave you want to set up in it. i.e. a 
5watt siganl vs a 10kW signal.
sure it seems obvious... you don't use radio shack stuff to hook you tx up 
to a 3 bay jampro.   But, why? so, I'm thinking about it like the string of 
inductors/caps in the thread and picture...

   Seems like as long as things are close to reasonable, it's fine.  But, 
when you push the limits, what happens?
  Which lets go first when the coax lets go? The first inductor / capacitor 
junction? Or the point where the first full quarter wave occurs?  How do you 
describe when the coax is breaking down... is it a failure of the conductors 
just due to the amplitude, or, a failure due to the lack of enough 
dielectric?  (f'rinstance, can you make a stranded RG58 center run down the 
center of a big enough foam filled line to handle the amplitude?  No... does 
the center just get hot due to the current?  RF current? would that mean 
there's a theoretically some frequency where you COULD do that?
So...
Does that mean that there is a point where there's not sufficient center 
conductor to allow the RF to be RF... it's actually so lacking in area for 
that "skin effect" that it become straight out electrical energy... and pops 
the center conductor?)

  Why can't you go the other way... 5 watts on the end of a piece of 1.5 
inch stuff.  Put the appropriately tuned... though rather small... antenna 
on the end for the freq. you're at... and it should work, right?  5 feet of 
it ... yeah... but a hundred??  Would the value of all the capacitance just 
"soak up" all the RF before you get to the end of the line.. ?  DO you just 
not have enough "oomph" to get the "skin effect" you need to set up a wave? 
That's what I think would happen... but maybe not.

Done properly, does any transmitter "see" anything beyond the first few feet 
if coax?  Probably not even the 'first few feet'...
 unless there's someting wrong.  although the tx does have to see the 
specified 50ohm to be happy... which I guess must be the antenna.  (or, the 
whole system?  hmmm. )

   This is another one of those "printable and bindable" threads.  I ought 
to be able to understand at least why a particular coax is appropriate for 
some given job... and which others I can get away with in a pinch... while I 
wait for the right stuff to get ordered. (Imaginary but possible 
scenario...)
??
Jason