Is a standing radio wave realistically possible?

Question

A perfectly directional wave should have constant dead points at integer multiples of it's wavelength, but in reality is it ever possible to have a deadpoint from a radio broadcast due to standing waves, assuming of course a static signal?

Answer 1

Generating a standing radio wave in a resonant cavity is the idea behind the klystron.

Answer 2

Don't confuse amplitude as a function of distance with magnitude as a function of time.

You get standing waves as a result of interference between the propagated wave and a reflection. (Examples: reflection from the far end of a string or from the end of an organ pipe.)

It's a very real problem if you are using v.h.f. handheld radios in a heavily built up area with reflection from buildings interfering (in the physics sense of interference) with the transmitted wave to produce 'dead spots' at regular intervals.

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Answer 3

Imbalanced loads or mismatched impedances can cause a standing wave.

If a standing wave is powerful enough it can damage wires and electronic components.

I have seen an imbalance on 60 hertz 120 VAC line, where the load (which was a saw), caused some sort of 'bad' mismatch. The powerline was burnt every interval where the amplitude of the current was spiked (overlapped) via standing wave.

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As far as radio waves? They travel through the air. They are basically let loose and free to propagate. The reciever can not 'create' standing waves from the incoming signal. Nor can the receiver retransmit a signal or reflect a signal back to the transmitter. It's about the 'air'.

Physically connected, say through a BNC cable, then you have the opportunity to see reflections.