MadSci Network: Physics

Re: radio reception at bends in underground tunnel

Date: Sat Apr 29 16:00:46 2006
Posted By: Madhu Siddalingaiah, Physicist, author, consultant
Area of science: Physics
ID: 1143412278.Ph

Hi Roland,

That's an interesting effect, but I have my doubts about any amplification
going on. Amplification implies that energy is being added to the system,
which requires a power source. I would guess that it's a coincidence
that signal improves around the bends, but I have no way to confirm that.
It's possible that the tunnel itself is acting as a waveguide and there are
antinodes at the bends, but that's pure speculation. I am surprized that
any signal gets through the tunnel at all!

To answer your second question, just about any effect that improves radio
reception can be used for antenna design. The real question is whether that
effect and geometry makes a good antenna. There are several qualities that
engineers look for in an antenna, such as size, effective aperture or
directive gain, band width, and efficiency. It's possible to make an
antenna that improves reception, but if it's limited to a very narrow band
or it's very inefficient, it might not be any better than any of the
numerous antenna designs that already exist.

Here is a general overview of antennas and some of the important

I hope that answers your questions!

Madhu - blog

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