# Suppose there is a standing wave in a transmission line at high power. Will the nodes of a wave 1 ft apart be hotter than the antinodes?

I was looking around for an evening and could not find an answer. I am also fuzzy on the exact electromagnetic physics principle of why a reflection occurs (please do not say "because the impedance did not match.") One explanation was that the electrical field changes mediums at the end of the line

I know this guess is probably wrong but I was thinking maybe a magnetic field follows the waves and dumps back into the transmission line similar to an inductor when disconnected from a circuit - electromagnetic interaction.

It depends if the dielectric losses are greater or the resistive losses.

The antinodes will be hotter if dielectric losses dominate The nodes will be hotter if resistive loses dominate.

The reflection happens because an open end on a trasmission line behaves like a voltage source that matches the incident signal. or because a short-circuit on a transmission like behaves like a source with the opposite voltage of the incident signal. an impedance mismatch is just a less extreme version of the above.

• So that is a yes .. there would be hot spots in the line if the nodes were far apart enough to make a difference .. "behaves like a voltage source that matches" true but that is not exactly what I am asking .. want the actual physical reason Commented Sep 14, 2021 at 3:42
• it's a "no" the nodes may actually be cooler. whay do you mean by "actual physical reason" Commented Sep 15, 2021 at 2:27

Nodes will be the hottest if resistance (conductor) losses dominate; antinodes will be hottest if dielectric losses dominate.

At lower frequencies, the conductor (usually copper) losses dominate - so the nodes will be hottest.

• if the nodes are 1 foot apart the frequency is about 300Mhz Commented Sep 18, 2021 at 2:23