‰  NOW 20 WPM  ‰  TEXT IS FROM JANUARY 2017 QST  PAGE 62‰

OTHER FORMS OF FILTERING ARE NOT AVAILABLE.  IT MAY ALSO BE USEFUL WITH
OLDER COMMERCIAL RADIOS THAT HAVE MINIMAL FILTERING BUILT IN.  RATHER THAN
PROVIDE THE USUAL ELECTRICAL FILTER RESPONSE PLOT TO DESCRIBE HOW WELL THE
FILTER WORKS, I USED A RATHER DIFFERENT TEST SETUP.  ON MY WORKBENCH, I FED
A SIGNAL FROM A SIGNAL GENERATOR INTO THE FILTER AND USED A SMALL SPEAKER
ON ITS OUTPUT.  THE SPEAKER HAS A LARGE PERMANENT MAGNET AND IS DESIGNED TO
NOT BE OVERLOADED EASILY.  APPROXIMATELY 1 INCH FROM THE SPEAKER, I PLACED
A SOUND LEVEL METER ON SOME FOAM INSULATION TO REDUCE VIBRATION.  THE
QUESTION THAT THIS TEST WAS TRYING TO ANSWER WAS, WHAT DOES THE FILTER DO,
AS HEARD BY YOUR EARS?  ONE OF MANY OFTEN CONFLICTING ONLINE REFERENCES
PROVIDED THE FOLLOWING VERY RELATIVE INFORMATION ABOUT SOUND PRESSURE LEVEL
‰  END OF 20 WPM TEXT  ‰  QST DE W1AW  ƒ