Radio Scanner

Discussion in 'Wireless & RF Design' started by mossman, Jan 20, 2011.

  1. mossman

    Thread Starter Member

    Aug 26, 2010
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    Can someone explain in very general terms how a wideband superhet radio scanner operates? We're talking about an older scanner (80's), which uses discrete circuity, etc. (no microprocessor) to quickly detect signals and also calculates and displays the frequency on a digital display. My main question is not how the signal is detected necessarily (single conversion to 2 MHz IF), but rather how the scanner knows which frequency it is receiving (i.e., so it can display the frequency on the LCD).
     
  2. nsaspook

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    Aug 27, 2009
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    Last edited: Jan 20, 2011
  3. mossman

    Thread Starter Member

    Aug 26, 2010
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    Ok, but this one does not. Can you explain how it determines the frequency for the readout?
     
  4. nsaspook

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    Last edited: Jan 21, 2011
  5. Kermit2

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    Feb 5, 2010
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    The radio MUST have a local oscillator for the mixer circuit, so that local oscillator must always remain above or below the received freq by the amount of the IF, in this case, 2 MHZ. What ever freq your local oscillator is feeding the mixer will determine what freq you are recieving.
     
  6. nsaspook

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    Aug 27, 2009
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    In this model the readout was the 'frontend/PLL divider code' needed to generate that local osc frequency (10.7mhz/455khz IFs) not the actual frequency.
     
    Last edited: Jan 21, 2011
  7. mossman

    Thread Starter Member

    Aug 26, 2010
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    Figured it out. Thanks.
     
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