‰  NOW 40 WPM  ‰  
EARLY TUBE DEVELOPMENT BY SAN FRANCISCO BAY AREA AMATEURS STARTING IN THE
YEAR 1907, AND DESCRIBES THEIR CONTRIBUTIONS THAT WOULD EVENTUALLY BUILD
WHAT IS NOW SILICON VALLEY.  YOU CAN WATCH THE ENTIRE VIDEO SERIES BY GOING
TO THE YOUTUBE PLAYLIST PAGE AT GOO.GL/LAL1AT. CONSIDERATIONS FOR AUDIO
OSCILLATORS DIGITAL AUDIO OSCILLATORS ARE NOT ALWAYS THE BEST ANSWER KLAUS
SPIES, WB9YBM  DIGITAL CIRCUITS HAVE BECOME SO UBIQITOUS THAT WE TAKE FOR
GRANTED THAT THESE TYPES OF CIRCUITS WIL

ASSEMBLE THE SPEAKER CAVITY AFTER THE GLUE ON THE SPEAKER AND COVER DISK IS
DRY, PLACE THE SPEAKER FACE DOWN ON A FLAT SURFACE SO THE MAGNET IS UP AND
THE SPEAKER CONTACTS ARE ON THE RIGHT SIDE, AS SHOWN IN FIGURE 1B.  SET THE
SPEAKER CAVITY TUBE DOWN ON A FLAT SURFACE SO THE HOLES FOR THE SWITCH AND
RCA PHONO JACKS ARE CLOSEST TO THE FLAT SURFACE.  APPLY A BEAD OF GLUE, 4,
AROUND THE TOP EDGE OF THE SPEAKER CAVITY TUBE.  TURN THE TUBE OVER GLUED
SIDE FACING DOWN AND ORIENT THE SPEAKER CAVITY TUBE, 5 FIGURE 1B.  LOWER
THE TUBE DOWN ONTO THE BACK OF THE SPEAKER FRAME.  APPLY A SMALL WEIGHT TO
THE SPEAKER CAVITY TUBE TO APPLY PRESSURE SO THE SPEAKER SELF ALIGNS TO THE
SPEAKER CAVITY.  LET THIS ASSEMBLY SIT UNTIL THE GLUE IS DRY.  AFTER THE
GLUE HAS DRIED, MAKE SURE TO REMOVE ANY EXCESS GLUE THAT MIGHT OVERLAP THE
OUTSIDE EDGE OF THE SPEAKER CAVITY.  THE OUTSIDE SURFACE OF THE SPEAKER
CAVITY MUST BE CLEAR OF ANY GLUE.  INSTALL SWITCH, RCA PHONO JACK, AND
WIRING INSTALL THE SWITCH, 6, AND TWO RCA JACKS, 7, INTO THE SPEAKER CAVITY
TUBE, 5.  REMOVE ALL THE HARDWARE FROM THE SWITCH AND USE ONLY THE LOCK
WASHER BETWEEN THE SWITCH BODY AND CAVITY, THEN ONLY ONE NUT TO SECURE THE
SWITCH HORIZONTALLY IN PLACE.  WHEN INSTALLING THE RCA PHONO JACKS, TIGHTEN
THEM IN PLACE WITH THE TWO GROUND LUGS TOUCHING EACH OTHER SO THEY CAN BE
SOLDERED TOGETHER.  WIRE THE SWITCH, SPEAKER, AND TWO RCA JACKS ACCORDING

TO THE SPEAKER HOOKUP DIAGRAM SEEN IN FIGURE 2.  WHEN VIEWING THE SPEAKER
CAVITY FROM THE BOTTOM, THE LEFT RCA PHONO JACK IS THE AUDIO IN, AND WITH
THE SWITCH LEVER ORIENTED TO THE RIGHT, WILL BE THE CW SPEAKERS ON
POSITION.  THE OTHER SWITCH DIRECTION WILL BE THE BYPASS POSITION.  NOW
STUFF THE COTTON BALLS, 8, IN AND AROUND THE SPEAKER EDGES AND BOTTOM OF
THE SPEAKER.  DO NOT OVERSTUFF TO WHERE IT WILL CREATE A BULGE IN THE
BOTTOM COVER.  WITH THE SPEAKER CAVITY IN THE SAME POSITION, APPLY A SMALL
BEAD OF GLUE, 9, AROUND THE BOTTOM EDGE OF THE SPEAKER CAVITY, WHICH AT
THIS TIME SHOULD BE FACING UP.  PLACE THE 2 3/8 INCH COVER DISK, 10, TO THE
BOTTOM EDGE OF THE SPEAKER CAVITY.  PVC STREET ELBOW MODIFICATION RESONATOR
USE THE FINISHED SPEAKER CAVITY AS A GUIDE TO ADD CLEARANCE NOTCHES FOR THE
SWITCH AND RCA JACKS TO THE PVC STREET ELBOW SEE THE LEAD PHOTO.  ADD
ENOUGH DEPTH TO THE NOTCHES SO THERES ABOUT 3/16 TO 1/8 OF AN INCH OF THE
SPEAKER CAVITY EXPOSED AT THE BOTTOM OF THE ELBOW.  I USED A DREMEL TOOL
WITH A SMALL CIRCULAR SANDING WHEEL NOT A DISK.  SET THIS ASIDE FOR THE
MOMENT.  FINAL ASSEMBLY  ATTACH AN RCA JUMPER CABLE TO THE CW SPEAKER AUDIO
‰  END OF 40 WPM TEXT  ‰  QST DE W1AW  ƒ