View Single Post
  #66   Report Post  
Old August 26th 06, 06:24 PM posted to rec.radio.amateur.antenna
[email protected] n3ox.dan@gmail.com is offline
external usenet poster
 
First recorded activity by RadioBanter: Jul 2006
Posts: 137
Default Mismatched Zo Connectors

I say it's 100 microjoules.

200W forward - 100W reverse = 100W net forward power. The percieved
issue of some people not believing in the seperate forward and
reflected waves just doesn't come in here... it's that the real part of
the Poynting vector is REDUCED by reflections. If you want to contest
this point then you need to tell me where the sign error is.

If you have a constant voltage (constant electric field) output on your
radio then this effect actually causes LOSS of power transfer through
even a lossless line.

You've got a 200W matched condition, power flux is 200W. You have 100W
reflected wave, you get a net power flux of 200W - 100W = 100W. You
can see this from the Poynting vector which is proportional to the
difference of the squares of the electric field amplitudes of the
forward and reflected waves. You can also do this with lumped circut
impedance analysis too.

If you can't bump Ef up by using an impedance matching network, the net
power flux is REDUCED by the reflected wave, and as such, the stored
energy in the fields in the line is ALSO reduced. If you can increase
the forward electric field in the face of mismatch, you can push the
200W into the load.

The reflected wave makes it so you need more voltage to push RF down
the coax.

Not 300 microjoules. 100 microjoules. The energy per unit length in
the line is proportional to the Poynting vector.



Dan