How frequencies are converted to prom bits

• 
  The VCO oscillator is first divided by a counter which is some multiple of 63 times. Then it is further divided by some multiple of 64 times and compared with the reference frequency.
  • 
    The formula for a stable phased lock loop is
    • 64 * A + 63 * B equals Frequency / Reference
      where
      A is a value between 1 and 63
      B is a value between 1 and 1023

  
  Example:
  A prom contains an A of 9, a B of 456, and reference of 5 kHz.
  9 x 64 + 456 x 63 = 29304
  29304 times 5 kHz. = 146.52 MHz Voile.
  
  Conversely, one often starts with a frequency, not with prom values.
  Divide 146.52 MHz by 5 kHz to get 29304 for the dual modulus system.
  Now determine A and B.
  But you can't easily find A and B with your calculator.
  How many 63's and 64's are in 29304? Use your computer and try this
  Simple BASIC program
  

  • for B = 1 to 1023
    • for A = 1 to 63
      • if B * 64 + A * 63 = 29304 then Print A,B

      next A

    next B

  

  The proms in Syntor, MCX-100, and Syntor X radios hold -

  • Sixteen bits of A and B information
    • Lets just look at the typical data in a prom -

    Address	00 01 02 03 04 05 06 07	
    Values   B  6  0  6  4  0  D  3
    

    
    

    B664	Defines the frequency.
    466B	Reverse order
    0100 0110 0110 1011	Convert to binary -
    0100 0110 0110 1011	10 bits for B and 6 bits for A -
    B = 0100011000 = 280	Complement the lsb
    A = 101010 = 42
    Complement the lsb
    64 x A + 63 x B = 20328
    Basic dual modulus algorithm
    20328 x 5 = 101640	Multiply by 5 kHz reference
    101640 + 322560 = 424200	Add UHF prescaler
    424.200 + 21.4 = 445.6 MHz	Add IF 21.4

    
    

  • What are the other 8 bits - D 3?
    • They select proper VCO subrange, Reference, front end and prescaler, depending on which radio.
  • Syntor X radios additionally hold tot, pl, scan, and priority channel data.

  

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