spot of DIY

one of those things we all need now and again.
http://vk5ajl.com/projects/SWRMeter.php
knowing the principals full well from my days in a radio job, so I had a go.
work you know but with one error swap names of FWR and REV meeasure port.
to this:

With matched terminations on the output ports,

1. A portion of the wave traveling from port 1 (input) to port 4 (output) is

coupled to port 3 (forward coupled), but not to port 2.

2. A portion of the reflected wave traveling from port 4 to port 1 is coupled

to port 2, but not port 3.

3. A portion of the wave incident on port 2 to port 3 is coupled to port 4, but

not port 1; and a portion of the wave incident on port 3 is coupled to port 1, but not

port 4.

 

thought I had a total miss-match with 50R load but did a few tests and googleing and got it right.

The reflected voltage is r times the incident voltage.  Since power is proportional to the square of the voltage, the reflected power, Prefl is (5/7)2 x 4 W = 2.04 W

and the power to the antenna = 4 W  - Prefl = 1.96 W

when I work out how to add gerber plot files I will

and a picture of my work.