Radio antennae


Does the shape of the antennae matter in regards to the wave length of the radio signal?

I saw somewhere that radio antennae have their rungs (I’m thinking of a ladder style antennae) spaced to match the length of the radio wave. So a higher frequency radio wave might have the rungs of the antennae spaced closer together (not sure if this is the right terminology, but picture old school TV antennae with a central pillar and “rungs” to either side).

Were old school antennae designed to have similar spacing as the actual length of the radio wave, or some multiple of the wave? How is this process interpreted and is this even a proper way to think of a radio receiver? Or is this just wrong. It seems to me that the wave lengths wouldn’t be more than a millimeter long.

In: 2

Yes, the length of the antenna matters.

Roughly, your antenna needs to be about the same size as the wave it’s receiving to work well. Radio waves run from hundreds of kilometers down to about a millimeter, but a millimeter is *really* high frequency (hundreds of GHz, up past WiFi).

Regular radio for TV or AM/FM broadcast is on the order of a few centimeters to a few meters, and the antennas match. Where it starts getting tricky is trying to design one antenna for multiple wavelengths. A big-ass dish works great but is impractical in a lot of situations. The multi “rung” antennas that you see on old TV rigs have multiple lengths and orientations to try and do a decent job of picking up a range of wavelengths from a variety of directions.

Some but not all antenna that use this concept. The “yagi” antenna one design you’re probably used to seeing on rooftops.

The desired wavelength affects the size and spacing of the elements. It’s common to have elements in units of half or whole wavelengths.

The length of radio waves varies from millimeters to many meters long. We’re probably tempted to think of them as small because they are invisible. But not all invisible things are small.