Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Should you hear static on a crystal radio?

  1. Jul 22, 2014 #1
    Hi, I'm hoping I'm in the right section, I wasn't quite sure.

    For a couple of days I've been trying with no success to make a crystal radio.
    To save me the trouble of having to build my own components, I decided to build a tuned circuit that should resonate at a radio frequency (and insert this tuned circuit into a crystal radio circuit) - if I did this and I happened to get an empty station (so if I had a comerical radio tuned to that frequency, I wouldn't hear anything either) would I be able to hear any static, or any indication that my crystal radio was constructed correctly and just needed to be retuned?
     
  2. jcsd
  3. Jul 22, 2014 #2

    NascentOxygen

    User Avatar

    Staff: Mentor

    Yes, definitely. As you connect and disconnect the clip to the aerial you'll hear static. If you live close to a radio station's tower the signal will be so strong that you'll be able to hear the station's program whether you have the tuning right or not. If you hear nothing but silence, maybe your crystal earpiece is not working?
     
  4. Jul 22, 2014 #3
    Ok, thanks for alerting me.
     
  5. Jul 23, 2014 #4

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    The amount of Power the crystal set will get down its antenna wire is very small. The programme you hear, even when it's tuned correctly, will only be at a low level. Unless you are in a very bad environment, the "static" signals are at a much lower level than a (usable) broadcast signal. So it is unlikely that you would hear that static at all. Normal radios (with amplification in them) increase the level of signals and make "static" audible.

    PS The term 'static' is used all over the place but it is not very well defined. Actors use it in films etc haha. Most of the odd signals you will hear on the mf bands will be other interfering stations; that would really be termed 'interference'. The other signals are often generated by sparks in machinery or lightning and might be referred to as static.
     
  6. Jul 23, 2014 #5

    NascentOxygen

    User Avatar

    Staff: Mentor

    Static is what you hear when you rub the alligator clip back and forth across the metal window frame. Not listening to distant electrical storms here.
     
  7. Jul 23, 2014 #6

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    'Static' means different things to different people. Most people who reckon they can hear static are not doing anything to the antenna wire or the mains supply. If it's impulsive interference then it is often (at least it was, when motor cars were real motor cars) due to car ignition circuits. I really don't like the use of that term because it is so poorly defined. The only 'static' discharge, likely to cause interference is surely lightning.
     
  8. Jul 23, 2014 #7

    NascentOxygen

    User Avatar

    Staff: Mentor

    It sounds like static, so we call it static. It probably is due to miniscule static dscharges, though, as no radio station signal is needed.

    Yes, a word with multiple personalities.
     
  9. Jul 23, 2014 #8

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    Sounds to me that 'static sounds like static' is not a definition and anything goes if you use it. There are many identifiable sources of interference but I can't think where the 'static' bit came in - if we ignore lightning (and the Neighbour's Whimshurst machine).
    Colloquial is fine when it does not mislead; that's my problem.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Should you hear static on a crystal radio?
  1. Crystal Radio (Replies: 2)

Loading...