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TUCoPS :: Radio :: pro34_1.txt

Realistic Pro-34 Mods


From: parnass@ihuxz.ATT.COM (Bob Parnass, AJ9S)
Subject: Eliminating a birdie in the PRO-34 portable scanner
Organization: AT&T Bell Laboratories - Naperville, Illinois
                   PRO-34 BIRDIE ELIMINATED

                     by Bob Parnass, AJ9S

   Birdies are unwanted signals generated within a receiver,
   which  cause the receiver to "hear itself."  Some birdies
   are caused by the unwanted product of the local  oscilla-
   tor.   Another  cause  is  a  stage, which oscillates but
   isn't meant to oscillate, such as a high gain  intermedi-
   ate frequency (IF) amplifier.

   Most birdies,  especially  those  generated  by  a  local
   oscillator,  are frequency stable.  It's difficult to rid
   a radio of these birdies, and solutions  usually  involve
   better internal shielding and isolation among the stages.

   A "wandering birdie"  is  one  which  changes  frequency.
   Wandering birdies, and birdies which appear and disappear
   suddenly, may be caused by  intermittent  ground  connec-
   tions within the radio, or defective bypass capacitors.


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