Cecil Moore wrote:

Many examples exist for current drops in distributed networks. That's
one thing that makes circuit analysis invalid for distributed network
problems. The series current is NOT the same value everywhere in a
distributed network. Asserting that there is no such thing as "current
drop" in distributed networks simply indicates an invalid choice of
models.

How much current drop is there at 440 MHz in 100 feet of RG-58 between
the source and a 50 ohm load? Answer: A 20 dB power drop equates to a
40 dB current drop.

Cecil,

You seem to like the "Roach Motel" theory of current flow. The electrons
check in, but they don't check out.

Here's a clue.

Conservation of charge is every bit as fundamental as conservation of
energy. Current does not just disappear. So what happens in your abused
RG-58 case?

Answer: this is not a simple series circuit.

At every point along the line the current splits between continuing down
the line and shunting to the other half of the transmission line. When
the line is lossless, the shunting is purely reactive, and no net
current flows. However, when there is loss in the line, there is a small
phase shift along with the attenuation, and net current is shunted.

The "circuit" model, as you like to call it, is every bit as valid as
the "distributed network" model. However, due to the distributed time
and space considerations in a transmission line, the "circuit" model is
mathematically intractable for many applications.

The physical reality remains the same even if we cannot easily do the math.

Oh, by the way, in a constant impedance environment the current change
corresponding to a power reduction of 20 dB is also 20 dB, not 40 dB.

73,
Gene
W4SZ