Most of the people interested in LF say that modern HF transceivers are usually unusable for 136kHz. RX portion of IC-751A seems to be good enough even for these "out of range" frequencies.
My own experience and modifications:
Mystery of RAM kept with lithium battery:
There is a RAM memory kept with lithium battery in this tcvr. The memory is placed on a small board EX-314. I was told by many people that this memory contains not only data stored by user, but even the controlling program of tcvr. In other words if battery fails tvcr becomes unusable and the whole tcvr (or at least the board) must be sent to Icom to be reprogrammed. There are also articles describing replacement of battery. See http://www.qth.com/KA9FOX/IC-751_battery.txt. I believed for long time that this "feature" applies to IC-751 model and not to the IC-751A. I asked many people about this and researched the Internet but nobody was able to give me a satisfactory answer. No word about this board is in Service manual which is detailed enough. I checked the battery and found that it still keeps 3 Volts, even after ten years . In spite of this I decided to avoid problems and to solve it in advance. I found 2 PCBs which can replace the original EX-314.
Nardo' Roberto (IK2RND) offers another. (send an e-mail asking for
details). I have chosen this one:
Built-in home-made AF filter:
To be able to receive extremely week CW signals on 136 kHz I fitted the transceiver with home-made AF filter.
............... 115 W,
3.5 MHz ............... 110 W
7 ... 14 MHz ..........100 W
10 MHz ...................95 W
21, 24 MHz .............93 W
28 MHz ...................87 W
Values are for CW and FM mode. With AM mode they are all almost exactly half.
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