ICOM transceiver IC-718 has an excellent receiver in spite of its low price. I can say that this device works better on low bands (40/80/160 m) after modification!. The receiving part (before the second RF-mixer) is completely same as in Kenwood TS-570D, but it has lower noise level in comparison with Kenwood.
I checked transceiver in PACKET, AMTOR, PACKTOR-I, CW, PSK-modes with KAMplus. Switching speed (TX/RX) for AMTOR is more than sufficient. For detailed characteristics look on site ICOM. I want to thank Vladimir - RK6FX for his ideas. So let's begin.
Remote top and bottom covers and turn transceiver over.
Swith on transceiver and turn the frequency to 100 kHz.
Connect RF-voltmeter to pin 12 of ACC-connector for TNC and adjust resistor R1104 until the minimum level of voltmeter scale. This resistor is located inside a soldered box on the board.