[CW] 600 Hz Resonant Speaker for CW - Plans

[Bob Good]

Jeff,  Can you explain a little more about the "reed" portion.  I cannot visualize the trimming but am familiar with the "cans".  Sorry but thanks for the help.....Regards,  Bob  K4BG
  ----- Original Message ----- 
  From: Jeffrey Herman 
  To: CW Reflector 
  Cc: cw at mailman.qth.net 
  Sent: Monday, August 31, 2009 9:16 PM
  Subject: Re: [CW] 600 Hz Resonant Speaker for CW - Plans


   I seem to recall an article about a VERY narrow CW mechanical filter, constructed as such: Take a pair of old headphone "cans", remove the outer plastic ear cover, then remove the metal diaphram. Using a metal cutter called a nipper (?), trim the diaphram in such a way that, for the most part, just a reed appears in the center (the longer the reed, the lower its resonant frequency, and vice versa). Replace the diaphram and cover. Now that particular earpiece will only pass signals whose audio freq'y exactly matches the reed's resonant freq'y.

  One of those "ah-ha" type of simple but effective projects.

  73, Jeff  KH6O





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