How does the size of an object affect RF propagation?

[barry.haworth]

Hi there, can anyone please advise how the size of an obstructing object affects the propagation of an RF transmission? Eg, for instance does refraction only occur in objects that are larger than the wavelength or does it occur in objects smaller than the wavelength? I can find heaps of info about RF propagation but very little on how the various phenomena such as absorption, reflection, refraction, diffraction, scattering etc is affected by the size of an object relative to the wavelength? I would appreciate any and all feedback. Many thanks

 

[M Quack]

Refraction will only occur on objects larger than the wavelength.
Isolated objects smaller than the wavelength will scatter.
A regular array of small objects with spacing similar to the wavelength will diffract.
Diffraction will also occur at the edges of large objects.

These are general wave phenomena, not limited to RF. You might get a better understanding if you also look at other kinds of waves, such as microwaves, visible light, and x-rays. Just don't study water waves too much, they are highly non-linear.

 

[KL7AJ]

Hi there, can anyone please advise how the size of an obstructing object affects the propagation of an RF transmission? Eg, for instance does refraction only occur in objects that are larger than the wavelength or does it occur in objects smaller than the wavelength? I can find heaps of info about RF propagation but very little on how the various phenomena such as absorption, reflection, refraction, diffraction, scattering etc is affected by the size of an object relative to the wavelength? I would appreciate any and all feedback. Many thanks

I just happen to be in the process of writing a book for the ARRL dedicated specifically to radio propagation, especially ionospheric.

But, you've had some good answers here, as ionospheric refraction is a very MACRO phenomenon. The ionosphere, as a whole has a very large "radar cross-section" but can also be extremely lossy...or not.

Stay tuned!

Eric

 

[barry.haworth]

Dear M Quack, thank you for your prompt reply, it was very useful. I appreciate your help!

Many thanks,

Barry

 

[barry.haworth]

Hi Eric, good luck with the book! Would love a copy when you get it published.
Many thanks,
Barry