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Antenna Design Filtering Out UnWanted Frequencies

  1. Feb 2, 2013 #1

    I was wondering if someone could explain to someone with no electrical engineering background where would one place the resonator whose sole responsibility is to amplify sine waves at a particular frequency while ignoring other sine waves. Would this resonator be located by the antenna itself or at a location once the signal has passed through the transmission line to the receiver for example ? I hope I have not confused the technology and further hope that I've explained the question clearly. Please correct me wherever and ask any questions for further clarification.

    NOTE: If this is not the correct forum for this question could anyone suggest a site that is better suited for this area of study.

    Thanks in advance
  2. jcsd
  3. Feb 2, 2013 #2


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    Staff: Mentor

    Hi victor43, http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

    That resonator is present in every TV and radio receiver. It is located inside the TV or radio set. It is called the tuner.

    Where signals are expected to be weak, the antenna is usually designed to be resonant at the frequency band of interest, too, to provide you with the strongest signal and least noise.
    Last edited by a moderator: May 6, 2017
  4. Feb 2, 2013 #3
    Thank you for the reply.

    I understand what you are saying but from a schematics diagram description where on the circuit would you find the tuner ? Would it be coupled to the antenna ?

    Thanks again
    Last edited by a moderator: May 6, 2017
  5. Feb 2, 2013 #4


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    Staff: Mentor

    The antenna lead goes direct to the tuner.
  6. Feb 2, 2013 #5
    Thank again for the reply.
  7. Feb 4, 2013 #6


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    If you really want your receiver to be selective (say you wanted to eliminate some very high power local interfering transmitter and only wanted to receive a narrow range of frequencies) you could put a filter (resonator) right at the output of the antenna and then take the feeder to the receiver on well screened cable. It's hardly worth that effort in most applications, though and you can get perfectly good filtering with a band-pass filter on the input to the receiver. The receiver (tuner) , itself does this but it may not perform well enough in the presence of =abnormal interference levels. When there is a particularly high level of interference at a frequency that is not what you actually need to receive, then it is possible to use a 'notch' or 'band-stop' filter into the feeder at the receiver input and remove the problem of the tuner becoming overloaded by the interference. Companies sometimes supply such filters to deal with interference sources if they happen to be putting out embarrassing level of interference at 'legal' levels which still are affecting local broadcast reception. Radar transmissions at airports can be a nuisance, for instance.
    Interesting that you use the word "amplify", in this context. A resonator may transform or 'magnify' the voltage but you need an active device like a transistor actually to 'amplify' a signal - i.e. to increase its Power. It is Power that counts when you are trying to discriminate between wanted signals and noise and interference.
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