View Single Post
  #135   Report Post  
Old June 25th 10, 09:27 PM posted to rec.radio.amateur.antenna
lu6etj lu6etj is offline
external usenet poster
 
First recorded activity by RadioBanter: Jul 2006
Posts: 143
Default what happens to reflected energy ?

On 25 jun, 10:00, Cecil Moore wrote:
On Jun 25, 2:13*am, lu6etj wrote:

In a TL, instead, total destructive interference in one point would
mean energy stop flowing from that point forwards (is it OK say
"forwards"?) and reverse its flow direction doubling his value, is it
OK?.


In our ham transmission line systems, the goal is to accomplish total
destructive interference toward the source, i.e. zero reflected energy
incident upon the source. So let's talk about destructive interference
toward the source and constructive interference toward the load.

You name it "redistribution" too, not reflection.


By definition, reflection is something that happens to a single wave.
By definition, superposition involves two or more waves. The
redistribution that I am talking about can include both reflection and
superposition if both are present. Depending upon the system
configuration, both may be present, both may be absent, or one exist
without the other.

Well, my
question was how we can set (devise) an experiment to get such
behaviour in a TL?


I've presented it before and it is a simple Z0-match involving a 1/4WL
matching section.

50w-----50 ohm------+------1/4WL 300 ohm------1800 ohm load

On the source side, rho at '+' is 0.7143

Using a TDR, we can verify that there is indeed a reflection from the
50/300 ohm impedance discontinuity. What happens to that reflection
during steady-state?

What happens to Vfor1(rho) = 50v(0.7143) = 35.7v?

What happens to Pfor1(rho^2) = 50w(0.51) = 25.5w?
--
73, Cecil, w5dxp.com


Sorry. Cecil, I do not catch you (final numeric example), would you
mind give to me a more explanatory/explicit answer? (the rest OK). 73
Miguel