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TECHNICAL REPORT:  
         
Kenwood TM742A Speaker Output Modification Using The Kennedy Technology FRS Module 
  


> Special Web Report:  06 Mar 2002 
   by John F. Reynolds, W5JFR 


I decided to try the Kennedy FRS set on my 1500 Goldwing so the passenger could hear and talk over the HAM Radio.  This could have been accomplished in many different ways.  However, I decided to give the Kennedy system a try.  As the normal speaker output from a Kenwood 741/742A is through a miniature phone jack on the side of the radio a slight modification is required so the sound will come through the Kenwood eight wire lead for the regular microphone. 

I started by removing the four screws that hold the bottom (non speaker side) on the radio.  Then loosened the four screws on the side of the radio, two on each.  A bit of leverage is required to remove the bottom of the radio.  Next I had to locate the normal speaker output at the miniature phone plug, as this was not easily accessible I traced it to its input at the front edge of resistor 2R7 from there I ran a jumper to pin seven of the microphone jack.  

This is located on the opposite side of the front circuit board. You will find eight pins, in rows of four.  The front will be 1-3-5-7 counting from the inside out.  Thus the rear pins will be 2-4-6-8. When pin seven is located the jumper can be completed.  

It is recommended that one use a fine insulated wire for this jumper, I used a wire that is also used for making wire wrap type circuits, it was eight inches long but I trimmed the non insulated portion of the ends to shorten it to six inches.  This modification requires a steady hand and a very fine tipped soldering iron. 

Now the sound from the Kenwood is routed to pin seven of the microphone lead and allows me and my passenger to hear the HAM through the Kennedy FRS set and this integrates the ham into the Honda sound system. When the microphone is keyed the passenger can also talk on the HAM. 

Thanks goes out to Carroll Walker who helped with the location of soldering points on the Kenwood 741/742A circuit board. 


John F. Reynolds, W5JFR, President MARC, 
MSGT, USAF Ret. (Security Police) 
Keep the frog on top and have a nice day. Rialto, CA. USA
  

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