‰  NOW 40 WPM  ‰  

OF THESE HISTORIC JEWELS TO LIFE IS A VERY REWARDING EXPERIENCE, WHETHER OR
NOT IT HAS BEEN MODIFIED.  FOR ME, PRESERVING THE ORIGINAL CIRCUITS IS THE
MORE RESPONSIBLE WAY TO GO.  BESIDES THAT, IF YOU EVER GET A B 17 FOR YOUR
SHACK, YOUR RADIOS WILL BE PLUG AND PLAY.  JOHN STANLEY, K4ERO, AND HIS
WIFE RUTH, WB4LUA, RETIRED TO RISING FAWN, GEORGIA AFTER 45 YEARS IN
INTERNATIONAL BROADCASTING, WHERE THEY DID ENGINEERING, CONSULTING, AND
TRAINING WITH CHRISTIAN RADIO STATIONS I

MODIFIED BY REMOVING THE ANTENNA INDUCTOR AND INSTALLING A LOADING
CAPACITOR.  THERE IS A SIMPLER WAY.  WE CAN CONNECT A FIXED CAPACITANCE IN
PARALLEL WITH THE 50 ANTENNA LOAD, AS SEEN IN FIGURE 4, WHICH WILL
TRANSFORM THE LOAD INTO A LOWER RESISTANCE.  FOR EXAMPLE, 900 PF FOR 7 MHZ
AND 1800 PF FOR 3R5 MHZ WILL MAKE THE TRANSMITTER SEE ABOUT 10 IN SERIES
WITH ABOUT 1000 PF.  THIS IS A LOAD THE TRANSMITTER CAN FEED PROPERLY.  WE
NEED ONLY USE A FEW TURNS OF THE ANTENNA INDUCTANCE AND ADJUST THE ANTENNA
COUPLING FOR THE DESIRED POWER OUTPUT.  KEYING THE TRANSMITTER  WE MUST
DEVISE A SAFE WAY OF KEYING THE FINAL STAGE OF THE TRANSMITTER TO OPERATE
CW.  THE ORIGINAL METHOD KEYED THE HIGH VOLTAGES COMING FROM THE DYNAMOTOR
VIA A RELAY.  ITS SAFER TO KEY THE INTERNAL RELAYS VIA THE KEY CONNECTION
WHICH WORKS FOR RELATIVELY SLOW CW OPERATION.  OTHER OPTIONS INCLUDE USING
GRID BLOCK KEYING, BY APPLYING A HIGH BIAS TO THE GRID OF THE FINAL TUBE
AND KEYING IT ON AND OFF.  THE BC SERIES TRANSMITTERS BRING OUT A GRID
CONNECTION TO THE REAR PLUG THAT CAN BE USED, HOWEVER, THE ARC 5
TRANSMITTERS DO NOT.  BE AWARE OF THE SOCKET DIFFERENCES BETWEEN ARC AND BC

MINIATURE BANANA PLUGS INSIDE THE HOUSING CAN AND SHOULD BE MADE WITHOUT
SOLDERING TO THEM.  POWER CONNECTIONS TO THE RECEIVER CAN BE MADE EITHER
VIA THE MALE DYNAMOTOR PINS OR VIA THE FEMALE SOCKET IN THE BACK.  IF YOU
INTEND TO USE A SPEAKER, YOU CAN FEED IT FROM THE BACK SOCKET, USING A
SMALL MATCHING TRANSFORMER AT THE SPEAKER.  MOST OF THE UNMODIFIED
RECEIVERS WERE DESIGNED TO FEED EITHER A 10 K LOAD OR A 600 HEADPHONE.
USING AN UNMODIFIED TRANSMITTER INVOLVES PROVIDING 24, 200, AND 550 V DC
VIA THE BACK PLUG AND CONNECTING THE OUTPUT TO YOUR ANTENNA.  ANTENNA
CONNECTION  THE ARC 5 RADIOS WERE ORIGINALLY MADE FOR AIRCRAFT ARC STANDS
FOR AIRCRAFT RADIO COMMUNICATIONS.  THEY WERE DESIGNED TO FEED INTO A
RELATIVELY SHORT WIRE ANTENNA FROM A FORWARD LOCATION BACK TO THE AIRCRAFT
TAIL.  THESE ANTENNAS TYPICALLY PRESENTED THE TRANSMITTER WITH 3 TO 10 IN
SERIES WITH A FEW HUNDRED PICOFARADS.  THE EXACT VALUES WOULD VARY WITH
FREQUENCY AND WITH THE LENGTH OF THE ANTENNA.  THUS, THE RADIO NEEDS A
MEANS TO MATCH THIS RANGE OF VALUES.  IF YOU OPERATE THE TRANSMITTER INTO A
SINGLE WIRE ANTENNA LESS THAN A QUARTER WAVELENGTH, THE TRANSMITTER WILL
PROBABLY FEED IT DIRECTLY.  HOWEVER, IF YOU WANT TO FEED A 50 COAX TO USE A
DIPOLE OR OTHER COMMON ANTENNA TYPE, THE OUTPUT NETWORK OF THE ARC 5
TRANSMITTER CANT LOAD PROPERLY.  THUS, MANY OF THE TRANSMITTERS WERE
‰  END OF 40 WPM TEXT  ‰  QST DE W1AW  ƒ