"But, radio waves can't travel through metal", I hear you say. Well, you know that, and I know that, so, let's do a experiment. If I use the best antenna (say those parabolic antenna thingies) against a thin sheet of metal, and use a extremely high wattage (say 100,000,000 watts), can the radio waves go through the metal? Or, could it melt the wall? Okay, okay. I know it sounds silly, but it's just a experiment, right?

According to Bing AI, it said, "Radio waves are affected by free electrons in electrical conductors such as metals and cannot pass through these materials. In a metal, there is a large number of freely mobile electrons available. When an electromagnetic (EM) wave, such as a radio wave, is incident on them, the electrons respond almost immediately to the oscillations. This response produces a magnetic field that joins with their electric field to produce EM radiation, and the phase is such that the transmitted wave is cancelled out. Therefore, metal absorbs radio waves"

  • $\begingroup$ Light doesn't travel through tick metal. Not true: if I put a high power light so an high power laser, I cut the metal, so the lights will pass.. If you change the "metal", you can do what you want, and you can do also with very low energy: just a magnet on an electromagnetic material... Just break the simplistic assumptions of Faraday cage (and thin metal is one of that). $\endgroup$ Dec 21, 2023 at 15:40
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    $\begingroup$ I think you're reading more intent to ridicule than actually exists, KC3WCR. That said, however, @GiacomoCatenazzi Please use comments only to discuss potential improvements to the question, not to write half-answers. $\endgroup$
    – Kevin Reid AG6YO
    Dec 23, 2023 at 1:14
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    $\begingroup$ @KC3WCR I really did not mean to make you feel like you're being laughed at! The contrary: I see how much you care, and that the conflicting statements you see must be frustrating to you! That's why I wrote an extensive answer that addresses the misconceptions you had individually, and explains what you might have gotten wrong when you presented them as common knowledge! Then I close with a concrete recommendation for learning material, and add a comic that praises people like you that are interested in learning. $\endgroup$ Dec 23, 2023 at 11:07
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    $\begingroup$ The key answer to this should mention both skin depth and penetration depth. $\endgroup$
    – user10489
    Dec 23, 2023 at 12:10
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    $\begingroup$ @KC3WCR, I think you’re running into mismatched expectations: regular visitors to the site expect questions here to be “well researched” as is clearly stated in the FAQs. This question appears to be completely unresearched as evidenced by its incorrect premise. beginner level/entry level questions are absolutely welcome here, but posters are expected to do a minimum amount of research, sharing what they’ve found so far in the post. Please don’t stop asking your questions! Please do start sharing the research you have done on them! $\endgroup$
    – webmarc
    Dec 23, 2023 at 15:32

1 Answer 1


"But, radio waves can't travel through metal", I hear you say.

Nobody says that. Why would they? Sure, conductive materials attenuate signal, and metals are typically very conductive, but real-world metal structures, often made of metals and alloys not optimized for high conductivity, are in fact plenty "RF transparent".

We do make simplifications like "a metal surface is a good reflector for RF", but it's not hard to keep in mind that it's only a good reflector, not a perfect one, and that it's a simplification.

Well, you know that, and I know that,

Well, I know it's wrong!

If I use the best antenna (say those dish antenna thingies)

A dish is just the reflector, not the antenna.

against a thin sheet of metal,

Thin, as well-known, means "lets through RF energy"; you'll want to read up on "skin depth".

It's really not a surprising concept if you know the physics: Maxwell's equations in materials simply allow for propagation of wave in anything but superconductive materials – and if your material is thin enough, yep, the wave will "travel through it" (the usual ray physics of partial reflection, diffraction and refraction still apply).

use a extremely high wattage (say 100,000,000 watts)

Why? Attenuation is something that happens as proportionality of output to input. So, instead of inserting 10⁵ W to get, say, 1 W out, insert 0.1 W in, and still get 1 µW out: that's very powerful for a radio receiver.

I know it sounds silly

Not at all. It just means you have a lot of things to learn about how RF waves actually work! So far you seem to be going from over-simplifications, and since you actually seem to care deeply about the matter, your only way forward here is to learn about the physics actually work.

Your approach of inserting high powers, thinking a dish is what makes for a good antenna, and the misconception that EM waves don't travel through metal suggest to me that you've been learning from bad educational material, and now you notice that what you've learned doesn't work in reality.

So, get better material to learn from! We don't know your background, so I don't think we can advise extremely well here, but:

You've got a general license; so, resistors, inductors and in general impedances do not scare you! So, maybe the ham-friendly style of Nahin's The Science of Radio (buy it used, maybe?) might be the right thing for you? It's a book that doesn't assume too much math (basically, just a bit of calculus), and goes into the topic from a radio operator's point of view, through historical steps.

Comic Advertisement for "National Radio Institute Education", from Nahin's book, where he used such ads lifted from 1970's fiction pulp magazines to brighten up the book's flow


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