Thread: Brainteaser
View Single Post
  #47   Report Post  
Old May 31st 06, 03:26 AM posted to rec.radio.amateur.antenna
Cecil Moore
 
Posts: n/a
Default Brainteaser

"Jim Kelley" wrote:
Very nice, Cecil. It would be also
useful to know how you obtained these
numbers.


The same way you obtained your numbers, Jim, when you said:

It follows that the initial reflection
would be 50 watts. When we assume that
everything is re-reflected from the
source, then at two seconds the forward
power at the front of the line would be
150 watts. At four seconds, 175 watts;
six seconds, 187.5; eight seconds,
193.75, and so on.


Please note that your numbers and mine agree exactly.
Also please note that I posted those numbers days ago
on qrz.com under a brainteaser thread. I have the EXCEL
file if you or anyone else would like to have it. (In a
one second long transmission line, when the load reflects
50 watts, it has essentially reflected 50 joules because
nothing changes during the following second.)

In fact, I'll present a challenge for you and everyone
else. In any one second long lossless transmission line
with any forward power and any reflected power, I defy
you to come up with an example where the number of joules
stored in the line is not equal to the forward power plus
the reflected power. Those joules are the joules sourced
by the generator that have not made it to the load. The
conservation of energy principle will have it no other
way. The laws of physics win once again.
--
73, Cecil http://www.qsl.net/w5dxp