Sound Card and Digital Interface for HF Rig

The Engineering Web

Enjoying the world of digital radio and also preparing for the Virginia QSO Party has forced my hand at selecting appropriate interfacing gear between my PC and my new Icom 746. Value is key so I will start with requirements...


Purpose: Establish connectivity between an Icom 746 and a PC to provide benefits including slave band switching of logging software to radio band changes, report of current frequency to logging software, computer control of WinKey CW interface, bidirectional audio interface for sound card HF modes, etc.

  1. Solution shall support PSK31 and similar modes.
  2. Radio and Computer shall have 100% DC electrical isolation.
  3. Solution shall support computer controlled CW keying.
  4. Solution shall slave band and frequency based on current radio settings.
  5. Solution may be contained in one assembly.
  6. Solution shall yield improvement in operator efficiency.
  7. Solution may utilize specific I/O of the Icom 746 Transceiver.
  8. Solution's timing should be immune to operating system task switching delays.

Breaking down the requirements further...

  • 1.1 - Interface shall provide an audio path from the Icom 746 receive audio to the computer sound card input.
  • 1.2 - Interface shall provide an audio path from the computer sound card output to the Icom 746 transmit audio input.
  • 1.3 - Passband for the audio path each direction will have a bandwidth between 300Hz to 3,000Hz.
  • 2.1 - Audio path from computer sound card to Icom 746 shall use transformer.
  • 2.2 - Audio path from sound card to Icom 746 shall use transformer.
  • 2.3 - The PTT function from the computer to the transmitter shall be opto-isolated.
  • 3.1 - The contest logging software shall key the transmitter in CW mode.
  • 3.2 - The solution may use the DTR line on the serial port for transmitter CW keying
  • 3.3 - The solution should use a WinKey interface between the PC and the transmitter
  • 4.1 - The solution shall support automatic update of logging software band selection within 1 second of a band change on the transceiver.
  • 4.2 - The solution shall support automatic update of logging software frequency within 1 second of a dial change on the transceiver.
  • 5.1 - The system may be contained in one assembly.
  • 7.1 - The system may use the ACC1 and/or ACC2 ports of the Icom 746 Transceiver.
  • 7.2 - The system may use the Remote Jack port of the Icom 746 Transceiver
  • 8.1 - A WinKey interface should be used for keying CW on the transceiver.

Next week we will review current offerings that solve the above requirements.


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