New video: Visualizing RF Standing Waves on mis-terminated transmission lines

[w2aew]

This video shows how standing waves are created on transmission lines from the addition of the forward (transmitted) wave and the reflected wave resulting from unmatched termination impedance.

[KD0CAC John]

Another good video , thanks again .
I wandered a while back that if measuring directly on feedline , that I should measure in multiple places , not just one spot .

[w2aew]

Another good video , thanks again .
I wandered a while back that if measuring directly on feedline , that I should measure in multiple places , not just one spot .

It all depends on the length of the line with respect to the wavelength of the signal being transmitted.

This also explains why - if you're having trouble adjusting your transmatch/tuner on a given band, that it can often help to add/remove some line between the tuner and antenna - because the impedance looking into a mismatched line will vary with line length (at a given operating frequency).  Adding or removing a bit of line can move the impedance off of a difficult-to-tune impedance extreme (node or anti-node).

[ElectroIrradiator]

That little experiment brings back memories.

Long time ago I literally measured the wavelength of an abused 2K25 X-band klystron by noting the distance between troughs in the standing wave reflected from a flat metallic surface, sitting perpendicular to the incident radiation. The metallic surface was a piece of polished PCB, and the slide it was riding on incorporated a micrometer. This was done because the 2K25 normally won't tune up into the 10GHz amateur band, but ... with a bit of help from a persuasion device...