• Question: I know I have asked alot of questions, but its interesting to find out! I go to a radio club in school, how does what we are saying on the radio get to everybody else's radio?

    Asked by ejrw to Adam, Catherine, Karen, Leila, Nazim on 15 Mar 2012.
    • Photo: Adam Stevens

      Adam Stevens answered on 14 Mar 2012:

      To get your voice onto the radio waves you have to ‘modulate’ the two signals. The basically just means putting the sound wave from your voice into the radio wave. There’s several ways to do this, the most common being FM or AM. Frequency modulation changes the frequency of the radio wave to carry your sound wave, whereas amplitude modulation changes the amplitude of the radio wave!

      The radios you use in club are probably AM, but they could be FM.

      Nowadays a lot of radios are digital so instead of sending your voice directly they change it into a digital signal (1s and 0s) and modulate that into the radio wave.

    • Photo: Leila Battison

      Leila Battison answered on 15 Mar 2012:

      That’s really interesting Adam, I didn’t know either. All I knew was that radio waves are used (rather than sound waves) because they are a kind of electromagnetic wave that has a very long wavelength (between 10cm and 10m) so they can travel very long distances without being ‘attenuated’ which means they don’t get weaker as they travel.

      Someone else uses a radio receiver to pick up the waves, but they can pick up all kinds of radio waves from lots of different sources, so you use a tuner to pick up a specific ‘frequency’, that’s the number that makes BBC Radio 1 97 to 99 FM 🙂

    • Photo: Karen Masters

      Karen Masters answered on 15 Mar 2012:

      Ooh great question. They are sent as signals on radio waves.

      Light makes up a tiny fraction of a massive spectrum of what we call “electromagentic radiation”. Basically it’s waves in the electric/magnetic fields. Different kinds of waves have different frequences – so radio waves are very long, and light is much shorter (the different colours of light show the different frequencies across just the bit of the spectrum we call light).

      I think in detail, the information is carried using a pattern of changes in some property of the radio waves – either the amplitude (how strong they are), or the exact frequency for example (radio wave go from metres long, to centimetres long). That pattern is made using a microphone which turns the sound waves from your mouth into an electrical signal which can make radio waves, and in the other person’s radio that process is reversed in the speaker.

      It’s quite clever really – and amazing to think it’s technology which has been around for more than 100 years now.

    • Photo: Nazim Bharmal

      Nazim Bharmal answered on 18 Mar 2012:

      Radio is a wave at high frequencies, and we can change those frequencies to put sound, voice, or any other sound into those waves. That is called modulation. Then the radio waves travel around the transmitter and excite the electrons in any aerials they hit. If the aerial is connected to a stereo which is tuned to the right frequency, then the electronics can demodulate the signal to reproduce the sound.

      Radio is one of the earliest electronic circuits that people have created, and at home we have a 80 year old radio made up of just 7 parts that still works and you can still tune it to radio stations: it is a bit weird hearing modern pop music coming out of a radio made before my dad was born!

Comments

  • Photo: Adam

    Adam commented on :

    Fun fact 2 – you can bounce shortwave (high frequency) radio off the ionosphere (top of the atmosphere), meaning that you can send radio signals to people on parts of the Earth you can’t even see! That’s why sometimes you can pick up random stations where there shouldn’t be any.

    Radio waves actually go up to km size wavelengths, as well (technically they can get as big as you want, but when you get down to such low frequencies they just get attenuated immediately).