What would the radio world look like?

Let’s say that I could see light in the FM radio part of the electromagnetic spectrum (say everything was blue-shifted for some reason) what would the world around us look like? Would large radio antennas stand out like a neon tube for example?

Also, if the goal of a receiving antenna is to capture enough of the radio energy to get a clear signal, why does a straight wire have an advantage over other configurations with a larger surface area? I could see how a radio dish would act similar to a glass mirror in an optical telescope, however other simple light detectors like the remote’s sensor on your TV rely on a large surface area rather than a thin thread. Please enlighten :slight_smile:

Yes, you’d see things light up according to their intensity and frequency. The sky would have an even glow to it, and point transmitters would glow like neon or fluorescent tubes.

As far as antennas go, the longer the conductor, the better the reception. I could get better reception with a metal sheet that is longer than a single wire; the length is most important. It’s also possible to build a yagi directional antenna with wire alone, no longer than a single wire, but with more gain. Radio wave detection relies how much current is induced in the antenna, so lengthening the antenna or focusing radio waves on a central conductor will lead to better reception.

Vlad/Igor

Also, since radio waves can be picked up inside buildings and through obstacles, I would imagine that the majority of solid objects that you could see would be translucent to some degree.

Here’s a nice picture of the radio sky at 408MHz.

I think that you got me towards the answer, an antenna is detecting a current induced by a magnetic field (I’m guessing) and a photo cell is detecting an electronic chain reaction caused by an atom absorbing a photon. Therefore they both would have different design considerations.

But what is it about radio light that makes its preferred means of detection so different from visible light?

Wavelength.

It would look like a fairly uniform blue glow. The problem is that the wavelengths in question are in the neighborhood of 3 meters. Unless your eyes were redesigned and scaled up to an incredibly large size, they would be little more than field strength detectors.

Yup, you’re right; I didn’t think about that part. You would see more RF bouncing around inside buildings, and it would be more difficult to make out some objects well because they wouldn’t block much RF at all. Things could get really confusing if you were in an urban area with several point sources (i.e. radio station transmitters).

Vlad/Igor

One thing that would be pretty bizarre is that from the a light source with “color” A, an object could appear as color “B” and cast a shadow of color “C”. Buildings and enclosures would appear as multicolored objects of various degrees of transparency.

I think it is pretty safe to say that even if your eyes could see FM in false color, your brain wouldn’t be wired in a way to make good sense of the world.

Antennas work best when they are the same length (or a multiple of the length) as the wavelength of the radio wave you are trying to receive. Even in something like a dish antenna, the dish isn’t really the antenna part. Its just a big reflector (like a mirror) that focuses the radio waves onto a smaller antenna. The actual receiving antenna is usually mounted on a pole attached to the center of the dish.

A large surface area is going to help you gather up the radio waves, but if the surface isn’t tuned to the frequency you want then most of the radio waves you gather up won’t get coupled into the antenna so you’re wasting most of your effort.

The light sensor on your TV isn’t a tuned antenna. Instead it relies on the property of semiconductor junctions that their conductivity is affected by light. The receiver in this case is actually fairly equally sensitive to a wide range of light frequencies. A piece of infra-red transparent plastic is placed over the receiver so that it only receives frequencies in the range that your remote puts out, and again a tuned circuit is used (most remotes pulse their infra-red at a frequency of about 44 kHz) so that signals other than the remote can be more easily ignored. It works a lot differently than a radio antenna.

If I could “see” FM, would I somehow be able to interpret Bruce Springsteen’s “I’m on Fire” playing on 93.1 KCBS-FM?

Something I just remembered is that if we could ‘see’ in the radio, then depending on the frequencies, Jupiter would be the ‘brightest’ object in the sky. We’d also be able to see radio galaxies– huge beautiful structures which emit in the radio wavebands.