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Subject: Icom 737 Transmit Mod File

Following is a copy from Packet, on how to do the transmit mod for the
well-reviewed. Icom 737 HF transciever.  If someone else tries it, please
let us know if it works.
73 from Leigh/KM6JE in Santa Barbara.
1300 B#  1312 ALL    IW3BKW WW     940312 ICOM IC-737 GEN.COVERANGE.
                         ICOM IC-737
1) Remove the top and bottom covers of the transceiver.
2) Remove the final power amplifier module.
3) Locate the LOGIC-UNIT on witch there is a back-up lithium battery
   for the RAM memory.
4) On the LOGIC-UNIT, near the chip called IC6 (TMP82C265BF-2),between
   the output pin PC06 and the imput pin PA15, find the diode D3.
5) This diode is not an SMD component.
6) Cut the diode D3.
..Now the ICOM IC-737 will transmit from 1,6 to 30 Mhz !!!.
73's de IW3BKW Riccardo @OE7XCI. ***
*** END OF MSG # 1300 from IW3BKW @ OE7XCI.#TIR.AUT.EU

From: (Greg Chartrand)
Subject: Icom 737 CW Filter Switching Mod.
Date: 15 Mar 1994 17:51:37 GMT
Organization: National Energy Research Supercomputer Center
Lines: 105
Message-ID: <2m4sj9$>
X-Posted-From: InterNews
Xdisclaimer: No attempt was made to authenticate the sender's name.

            CW Filter Switching Modification for the Icom 737

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.


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

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.

Good luck! 73's
Greg Chartrand

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


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