ICOM IC-737

1- REMOVE POWER AND ANTENNA.
2- REMOVE SCREWS AND OPEN THE COVER.
3- REMOVE SCREWS AND OPEN THE BOTTOM COVER
4- REMOVE THE SCREWS AND REMOVE THE  PA  UNIT
5- REMOVE THE SCREWS AND FOLD OUT FRONT DISPLAY.
6- LOCATE LOGIC UNIT ON BACK OF THE RADIO
7- LOCATE DIODE  D3  ON THE LOGIC CIRCUIT BOARD.
8- CUT DIODE  D3.
9- REASSEMBLE THE RADIO.

NOTE: THE UNIT BOARD IS THE BOARD WITH A BATTERY IN YOUR LEFT. 

..Now the ICOM IC-737 will transmit from 1,6 to 30 Mhz !!!.
 

 

Mod complete.
Not responsible for errors on your part.

 

The Icom 737 is a wonderful radio for CW operation, but I did not like the filtering switching options offered in normal operation of the radio when you have installed BOTH the 9 Mhz and 455 Khz optional CW filters. The default option is to use the SSB filter for CW in the CW mode, and then switch in BOTH the 9 Mhz and 455 Khz optional IF filters in the CW-N mode. This provides too broad a filter for general tuning in CW, and the CW-N mode (with the two filters in) is far too sharp for just tuning around.

I felt that it would be better to allow the 455 Khz filter to be functioning full time in the CW mode, and then switch in the 9 Mhz CW filter in the CW-N mode. The following simple modification only requires a single wire to added to the radio.


MODIFICATION
 

1. Remove the top/bottom cover of the radio as per the manual.
   
    
2. Position the radio facing you and locate the resistor R-323 which is simply labeled "323" on the PC board just to the left of the opional 455 Khz CW filter. Solder a wire to the end of R-323 which is closest to the front pannel.
   
    
3. Locate J-3 just above and to the right of the 9 Mhz filter F-13. Attach a wire to the connector or wire going to pin 7. Pin 7 is the third pin from the right. (The pins are numbered 1-9 from left to right) You may carefully tack solder a wire to the plug by removing it first. I used a solid 28 gauge wire and just pushed it into the connector without soldering.
   
    
4. Replace the top and bottom covers.

I'm happy with the function of this modified switching arrangement. The CW-N function is now the mode of last resort when going after the weak ones, or when the QRM gets out of control, and tuning with just the 455 Khz filter is a better than using the SSB filter.


 

                                     Pin 7 of J3
                                      _________ 
                                     |ooooooooo|
                                            |
                               ____________ |_
                              |     F13    |  |
                              |____________|  |
                                              |
                               ____________   |
                              | CW FILTER  |  |
                              |____________|  |
                                              |
                                              |
                                              |
                                              |        |   ------------
                                              |        -  |   CW      |
                                    New wire >| R-323 | | |  FILTER   |
                                              |        -   ------------
                                              +--------|

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