How are radio waves created when we send information with things like computers? Is it similar to how larger radio waves from radio towers are made?

Question

How are radio waves created when we send information with things like computers? Is it similar to how larger radio waves from radio towers are made?

In: 3

Answer 1

Yes same idea, just smaller.

Imagine something like a champagne glass. When you tap it, you hear a tone- that tone is because the size and shape of a material give it a *resonant frequency*, meaning a vibration travels back and forth through the material that many times per second.

When an opera singer shatters a champagne glass, that’s because her voice exactly matches the resonant frequency of the glass. So the sound pressure waves from her voice exactly match the back and forth vibrations of the glass, meaning that the vibration in the glass increases with each sound wave from her voice. Eventually it increases beyond the strength of the glass, and the glass shatters. But before it does, her and the glass are both VERY loud.

Antennas work much the same. An antenna of a particular design has a particular resonant frequency. So you have to size your antenna to the frequency you want to transmit. The easiest way to do this is to just have the antenna be the same wavelength as the radio wave, or some perfect multiple or fraction of it.

For example, a 100 MHz FM Radio antenna should be almost exactly 3 meters long.

Computers however use MUCH higher frequencies, and much shorter ranges. WiFi and Bluetooth for example, use 2.4 GHz (2,400 MHz). That means a full-wave antenna would be 12.5cm long, or about 5 inches. However at these frequencies a 1/4 wave antenna works quite nicely, which is an inch or so long.

With that small of an antenna, it’s often easier to just print the antenna on the same circuit board as the rest of the gadget rather than having an external antenna. For example, consider [this module](https://usa.banggood.com/E103-W01-WIFI-ESP8266EX-2_4GHz-100mW-PCB-Antenna-IoT-UHF-Wireless-Transceiver-ESP8266-Transmitter-and-Receiver-RF-Module-p-1512018.html?cur_warehouse=CN)- this is a small WiFi radio and antenna module, someone who is building a gadget and wants to integrate WiFi can simply include this part rather than designing their own WiFi system. The squiggly line is actually the antenna- at short range, it works just fine. If you look at ‘recommended’ at the side you see a few other similar modules.