Tarmo Tammaru wrote:
Roy,

You are cheating. In the steady state there is no load on your source.
Regardless of what the Bird meter reads. Do one of the following:

Why is this cheating? There is reverse power on the line. The source is
not absorbing the reverse power. You and others have said, without
qualification, that it does. I've shown a case where it doesn't.

1.Short the end of the 1/2 wave line.
2.Use a 1/4 wave open ended line.
3.Get a pulse generator, 0 Ohm output impedance +50 Ohm series resistor. Set
the pulse with to 100ns and 1V, and use an arbitrary length of coax, either
open or shorted, but longer than 100ns. Grab a 'scope and look at the
junction of the coax and the 50 Ohm resistor. You will be able to see the
.5V reflected pulse appear across the 50 ohm resistor. ALL of the reflected
energy was absorbed, and half of the forward power.

When talking of amateurs and transmitters, we're dealing with
sinusoidal, steady state conditions. You've just described a transient
pulse situation. It's different in several ways, one of the most
important being that the source is off when the returning pulse arrives.
I'm fully able to discuss TDR phenomena, but it's not relevant, and only
adds confusion to a discussion of amateur transmitters and transmission
lines.

In sinusoidal, steady state conditions, it's absolutely incorrect to say
that the reflected power is absorbed by the source, whether the source
is matched or not. And it's easy to show it's incorrect, as I've done.

Roy Lewallen, W7EL


Tam/WB2TT
"Roy Lewallen" wrote in message
...

Sigh. I guess one more time. A mouse in the maze.

70.7 volt RMS voltage source, 50 ohm series resistor. Connect to an open
circuited, half wavelength transmission line. Put your magic lossless
Bird wattmeter in the line and measure the forward and reverse power:

Pf = 100 watts
Pr = 100 watts

The "transmitter" is perfectly matched to the line.
The "reflected power" is 100 watts.
The dissipation of the "transmitter" source impedance is zero. Not 100
watts. Not even one watt. Zero.

No, how can anyone possibly say that when the transmitter is matched,
the reflected power is absorbed by the transmitter?

Any number of other examples can easily be found. You'll find a few
others in the "Food For Thought" series available from
ftp://eznec.com/pub/food_for_thought/.

I'm firmly in agreement with Bill and Ian on this one.

Roy Lewallen, W7EL