Tam/WB2TT wrote:
"Cecil Moore" wrote:

The forward current and reflected current cancel at the mouth of
the shorted 1/4WL stub. However, they add in-phase 1/4WL away at
the short, maybe to many amps of RF current at the shorted end.
Since there is no physical impedance at the mouth of a stub, nothing
except superposition of forward and reflected waves happens there
and nothing except a virtual impedance exists there. All of the action
is at the shorted end of the stub where there exists 100% reflection.

I just did the simulation again, and you are right. For a 1V signal feeding
a 50 Ohm line through a 450 Ohm series resistor, there is 20 ma of
current flowing through the short. Don't understand why I didn't see it the
other time. There is 0 current through the 450 Ohm resistor.

Install a Bird wattmeter at the 450 ohm resistor and you will read
forward power and reflected power. The *net* current through the 450
ohm resistor is zero. The forward current is not zero. The reflected
current is not zero. Their magnitudes (10 ma?) are equal and their phases
are 180 degrees from each other so they cancel to net zero current.

If we take the forward current at the 450 ohm resistor as a reference of
10 ma at zero degrees, the reflected current will be 10 ma at 180 degrees.
Those two current signals add up (superpose) to zero at the resistor.
--
73, Cecil http://www.qsl.net/w5dxp



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