    _____________
     |           
     |                      J-POLE ANTENNA
     |                    ** NOT TO SCALE **
     |                ** DIMENSIONS FOR 146MHz **
    56.39"       
     |           
     |     ______
     |      |      
     |      |      
     |      |                                
     |      |                ** NOTE: ALL    
     |    19.71"             MEASUREMENTS      
     |      |    ------      TO THIS POINT                
     |      |        3"           -------->  
  ---'------'----ͼ----      I.E. BOTTOM        MAX
                              OF "J"          <-- 2--->
                                                 IN.
                                                 (NOT CRITICAL)


      THE FEEDPOINT IS APPROX. 3" FROM THE BOTTOM OF THE J AND IS
      FED USING A BALUN OF 26-3/4" IN LENGTH CONSTRUCTED AS FOLLOWS:

              Ŀ  
             
                   LENGTH
                   OF CO-AX
                   OF BALUN
                   = 26-3/4"
                
                
              
              

            TO RIG

      * * * NOTE ==> CO-AX USED MUST BE SOLID POLYETHYLENE. THERE IS A
                     DIFFERENT VELOCITY FACTOR FOR FOAM-TYPE.
                     THE VELOCITY FACTOR USED FOR POLYETHYLENE
                     IS 0.66
                                0.66 * 5904 = 3897 USED IN
                                FORMULA. IF YOU USE FOAM
                                CO-AX, FIND THE CORRECT
                                VELOCITY FACTOR AND RECALCULATE
                                THE LENGTH OF THE BALUN.


            FORMULAE TO COMPUTE LENGTH OF ELEMENTS & BALUN IN INCHES
            SHORT ELEMENT    (2878/fMHz)
            LONG RADIATOR    ((K*(5904/fMHz))+(2878/fMHz))
            BALUN            (3897/fMHz)

    CONSTRUCTION: OUT OF 1/2 INCH COPPER PIPE, USING ONE 90 DEGREE
                  ELBOW AND ONE TEE. SOLDER (REMEMBER TO USE PLUMBING
                  SOLDER - SOLID WIRE, AND ACID FLUX; USE A PROPANE
                  BLOW TORCH OR SIMILAR HEAT SOURCE.

                  THE CONNECTION FROM THE BALUN IS MADE USING 5/8 INCH
                  HOSE CLAMPS, WITH THE WIRE SLIPPED IN AGAINST THE PIPE.

                  THE FEEDPOINT IS INITIALLY SET AT 3 INCHES FROM THE
                  BOTTOM OF THE J.  USING AN SWR METER OR BIRD
                  WATTMETER, SLIDE THE TAP TO LOCATE THE MINIMUM SWR.

